OBD2 Codes List and Meaning [Signs, causes & diagnostic procedure]

If you’re new to diagnosing vehicles and are wondering what the different OBD2 codes or diagnostic trouble codes mean, then you’re in the right place. Many times, users utilize OBD2 diagnostic scanners to find out why their car check engine light is on. And when the codes appear on the screen, many people are not able to comprehend what the different codes stand for.

To make your work easier, we researched many diagnostic trouble codes and their meaning so that you can have an easy time knowing why the check engine light is on and repair your car where needed. These codes also let you have a rough estimate of the repair as you can tell which part has a problem.

OBD II codes belong to four groups, which are as follows:

Powertrain (P) Codes
Chassis (C) Codes
User network (U) Codes
Body (B) Codes

What you need to know about OBD2 Codes

Before we look at the OBD2 codes list, it is vital to understand the basics of OBD II codes; so that we can have an easy time interpreting them.

What is OBD?

OBD in full means onboard diagnostics. Also, it is the vehicle’s electronic system that performs self-diagnosis and reporting. Hence, if a problem is noticed, the system registers it as a unique code. That particular code is referred to as a diagnostic trouble code (DTC). If you’re diagnosing the car, you can get that code and interpret it to know the type of issue you’re facing. For instance, if the vehicle gives you the …. Code, this implies that there is a …. So, your job is to detect the problem and rectify it.

The good news is that some advanced diagnostic scanners explain what the trouble code means and help you to have a rough idea of where to look or what part of the car to check. Note that OBD II codes are trouble codes that are specific to OBD II-compliant vehicles only. These feature vehicles manufactured from 1996 and newer domestic, European, and Asian.

How to interpret the digits in OBD2 codes:

Interpreting and using OBD2 scanner codes is not difficult as it provides monitoring for different systems. Some of the systems are powertrain, chassis, body, user network, and much more. Identifying the vehicle system with a fault is simple by looking at how the code appears.

Here is how you can identify a fault code:

The First Character (Letter)

Every OBD2 code begins with a letter that denotes the section of the car that has a problem. Here are different letters with the parts that they represent.

P – Powertrain: this represents the engine, transmission, and all the accessories linked to it.

C – Chassis: it features mechanical systems and functions such as suspension, steering, and braking.

U – User network & vehicle integration: it covers functions that are managed and shared by onboard computer systems.

B – Body: it represents parts that are mainly found in the passenger compartment area.

The second character (Number)

After identifying the letter, the next step is to identify the number. DTCs come with either “0” or “1”.

0 – if the number is “0”, then the code is a generic or standardized code

1 – if the number is “1”, then it is a manufacturer-specific code

The third character (Number)

0 – Fuel & air metering and auxiliary emission controls

1 – Fuel & air metering

2 – Fuel & air metering (injector circuit)

3 – Ignition systems or misfires

4 – Auxiliary emission controls test

5 – Vehicle speed control & idle control systems

6 – Onboard computer & output circuit

7 – Transmission

The fourth character (Number)

The final section of the diagnostic fault code is a two-digit number. This number indicates the real issue you’re facing. The two numbers fall between 0 and 99. From our DTCs below, you can clearly see that every error code features five characters, which allows you to interpret the code.

Without wasting any more time, here are some of the codes with their meaning.

OBD2 Codes List

P0001 -Issue with the Fuel Volume Regulator Control Circuit

P0002 -Fuel Volume Regulator Control Circuit Range/Performance down

P0003 -Low Fuel Volume Regulator Control Circuit Problem

P0004 -High Fuel Volume Regulator Control Circuit Problem

P0005 -An Open Circuit Fuel Shutoff Valve “A” Control

P0006 -Fuel Shutoff Valve “A” Control Circuit Low

P0007 -Fuel Shutoff Valve “A” Control Circuit High

P0008 -Misalignment in the Engine Position System Performance Bank 1

P0009 -Variation in the Engine Position System Performance Bank 2

P0010 “A” Camshaft Position Actuator Circuit Bank 1 Malfunction

P0011 – It indicates a problem with the timing of your “A” camshaft.

P0012 -Malfunctioning “A” Camshaft Timing Over-Retarded (Bank 1)

P0013 -VVT solenoid or Actuator Circuit has worn out

P0014 – It shows the B camshaft on bank 1 is over-advanced.

P0015 -“B” Camshaft Position – Timing Over-Retarded than PCM

P0016 -Crankshaft Position – Camshaft Position Correlation (Bank 1 Sensor A)

P0017 -Issue with camshaft and crankshaft

P0018 -Crankshaft Position – Camshaft Position Correlation (Bank 2, Sensor A)

P0019 -Crankshaft Position – Camshaft Position Correlation (Bank 2, Sensor B)

P0020 -“A” Camshaft Position Actuator Circuit (Bank 2)

P0021– Incorrect Camshaft variable timing solenoid

P0022– “A” Camshaft Timing Issue

P0023– “B” Camshaft Position – Actuator Circuit

P0024– “B” Camshaft Position Timing Over-Advanced

P0025– “B” Camshaft Position – Timing Over-Retarded

P0026– Intake Valve Control Solenoid Circuit Malfunction

P0027– Problem with the Exhaust Valve Control Solenoid Circuit

P0028– Intake Valve Control Solenoid Circuit Malfunction (Bank 2)

P0029– Exhaust Valve Control Solenoid Circuit Range/Performance

P0030– Primary HO2S Heater Control Circuit Malfunction

P0031– Low Voltage at HO2S Heater Control Circuit (Bank 1, Sensor 1)

P0032– High Voltage at HO2S Heater Control Circuit (Bank 1, Sensor 1)

P0033– Turbo Charger Bypass Valve Control Circuit

P0034– Low Voltage at Turbo Charger Bypass Valve Control Circuit

P0035– High Voltage at Turbo Charger Bypass Valve Control Circuit

P0036– HO2S Heater Control Circuit Malfunction (Bank 1, Sensor 2)

P0037 – This error code denotes an issue with the oxygen sensor heating element for the sensor installed in the bank 1 sensor 2 positions.

P0038– HO2S Heater Control Circuit (Bank 1, Sensor 2) High

P0039– Turbo/Super Charger Bypass Valve Control Circuit Malfunction

P0040– O2 Sensor Signals Swapped (B1 S1/B2 S1)

P0041 -O2 Sensor-related problems at Bank 1 Sensor 2/ Bank 2 Sensor 2

P0042 -HO2S Heater Control Circuit (Bank 1 Sensor 3)

P0043 -Low Voltage at HO2S Heater Control Circuit (Bank 1 Sensor 3)

P0044 -High Voltage at HO2S Heater Control Circuit (Bank 1 Sensor 3)

P0045 -Turbo/Super Charger Boost Control Solenoid Circuit/Open

P0046 -Turbo/Super Charger Boost Control Solenoid Circuit Range/Performance

P0047 -Low Voltage at Turbo/Super Charger Boost Control Solenoid Circuit

P0048 -High Voltage at Turbo/Super Charger Boost Control Solenoid Circuit

P0049 -Turbo/Super Charger Turbine Overspeed

P0050 -HO2S Heater Control Circuit Malfunction (Bank 2, Sensor 1)

P0051 -Low Voltage at HO2S Heater Control Circuit (Bank 2, Sensor 1)

P0052 -High Voltage at HO2S Heater Control Circuit (Bank 2, Sensor 1)

P0053 -HO2S Heater Resistance (Bank 1, Sensor 1)

P0054 -HO2S Heater Resistance (Bank 1, Sensor 2)

P0055 -HO2S Heater Resistance (Bank 1, Sensor 3)

P0056 -HO2S Heater Control Circuit (Bank 2, Sensor 2)

P0057 -Low Voltage at HO2S Heater Control Circuit (Bank 2, Sensor 2)

P0058 -High Voltage at HO2S Heater Control Circuit (Bank 2, Sensor 2)

P0059 -HO2S Heater Resistance (Bank 2, Sensor 1)

P0060 -HO2S Heater Resistance (Bank 2, Sensor 2)

P0061 -HO2S Heater Resistance (Bank 2, Sensor 3)

P0062 -HO2S Heater Control Circuit (Bank 2 Sensor 3)

P0063 -Low Voltage at HO2S Heater Control Circuit (Bank 2 Sensor 3)

P0064 -High Voltage at HO2S Heater Control Circuit (Bank 2 Sensor 3)

P0065 -Problem with the Air Assisted Injector Control Solenoid Valve

P0066 -Air Assisted Injector Control Circuit Low

P0067 -High Voltage at Air Assisted Injector Control Circuit

P0068 -MAP/MAF – Throttle Position Mismatch

P0069 -Manifold Absolute Pressure – Barometric Pressure Mismatch

P0070 -Ambient Air Temperature Sensor Circuit Malfunction

P0071 -AAT Sensor Range/Performance

P0072 -Low Voltage at Ambient Air Temperature Sensor Circuit

P0073 -High Voltage at Ambient Air Temperature Sensor Circuit

P0074 -Ambient Air Temperature Sensor Circuit Not Constant

P0075 -Intake Valve Control Solenoid Circuit (Bank 1) Malfunction

P0076 -Intake Valve Control Solenoid Circuit Malfunction (Bank 1)

P0077 -High Voltage Intake Valve Control Solenoid Circuit (Bank 1)

P0078 -Exhaust Valve Control Solenoid Circuit Malfunction (Bank 1)

P0079 -Low Voltage at Exhaust Valve Control Solenoid Circuit (Bank 1)

P0080 -High Voltage at Exhaust Valve Control Solenoid Circuit (Bank 1)

P0081 -Intake Valve Control Solenoid Circuit Not Functioning Correctly (Bank 2)

P0082 -Low Voltage at Intake Valve Control Solenoid Circuit (Bank 2)

P0083 -High Voltage at Intake Valve Control Solenoid Circuit (B2)

P0084 -Exhaust Valve Control Solenoid Circuit Malfunction (Bank 2)

P0085 -Low Voltage at Exhaust Valve Control Solenoid Circuit (Bank 2)

P0086 -High Voltage at Exhaust Valve Control Solenoid Circuit

P0087 -Low Pressure at Fuel Rail/System

P0088 -High Pressure at Fuel Rail/System

P0089 -Problem With Fuel Pressure Regulator 1

P0090 -Fuel Pressure Regulator 1 Control Circuit Malfunction

P0091 -Low Voltage at Fuel Pressure Regulator 1 Control Circuit

P0092 -High Voltage at Fuel Pressure Regulator 1 Control Circuit

P0093 -Large Leakage in the Fuel System

P0094 -Small Leakage in the Fuel System

P0095 -Intake Air Temperature Sensor 2 Circuit Malfunction

P0096 -Intake Air Temperature Sensor 2 Circuit Range/Performance Not Matched

P0097 -No Voltage at Intake Air Temperature Sensor 2 Circuit

P0098 -High Voltage at Intake Air Temperature Sensor 2 Circuit (Bank 1)

P0099 -Intake Air Temperature Sensor 2 Circuit Malfunction

P0100 -Faulty MAF Sensor or CircuitP0086 -High Voltage at Exhaust Valve Control Solenoid Circuit

P0101 – The OBD2 code alerts you there’s an issue with your mass air flow sensor.

P0102 -Low Input at MAF Circuit

P0103 -High Input at MAF Circuit

P0104 -Mass Air Flow “A” Circuit Intermittent

P0105 -Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction

P0106 -Manifold Absolute Pressure/BPC Range/Performance Mismatch

P0107 -Low Input at Manifold Absolute Pressure/Barometric Pressure Circuit

P0108 -High Input at Manifold Absolute Pressure/Barometric Pressure Circuit

P0109 -Manifold Absolute Pressure/Barometric Pressure Circuit Not Continuous

P0110 -Bank 1 Intake Air Temperature Sensor 1 Circuit Malfunction

P0111 -Mismatched Intake Air Temperature Sensor 1 Circuit Range/Performance

P0112 -Intake Air Temperature Sensor 1 Circuit Voltage Too Low

P0113 – The OBD2 code indicates a problem with your intake air temperature sensor.

P0114 -Intake Air Temperature Bank 1 Sensor 1 Circuit Malfunction

P0115 -Faulty Engine Coolant Temperature Circuit

P0116 -Incorrect ECT Circuit Range

P0117 -Low Voltage Output at Engine Coolant Temperature Circuit

P0118 -High Voltage Output at Engine Coolant Temperature Circuit

P0119 -Engine Coolant Temperature Circuit Sensor 1 Malfunction

P0120 -Faulty Throttle/Pedal Position Sensor/Switch “A” Circuit

P0121 -Throttle/Pedal Position Sensor/Switch “A” Circuit Range/Performance

P0122 -Low Voltage Output at Throttle/Pedal Position Sensor/Switch “A” Circuit

P0123 -High Voltage Output at Throttle/Pedal Position Sensor/Switch “A” Circuit

P0124 -Throttle/Pedal Position Sensor/Switch “A” Circuit Out of Range

P0125 – It means there is a problem that your engine does not reach the proper operating temperature.

P0126 -Insufficient Coolant Temperature or faulty thermostat

P0127 -High Intake Air Temperature

P0128 – It denotes that your vehicle’s engine isn’t staying hot enough.

P0129 -Barometric Pressure Too Low

P0130 -O2 Sensor Circuit Malfunction (Bank 1, Sensor 1)

P0131 -Low Voltage Output at O2 Sensor Circuit (Bank 1, Sensor 1)

P0132 -High Voltage Output at O2 Sensor Circuit (Bank 1, Sensor 1)

P0133 -O2 Sensor Circuit Slow Response

P0134 -O2 Sensor Circuit Completely Stops Working

P0135 – It shows you that the heating circuit in your oxygen sensor is malfunctioning.

P0136 -Faulty O2 Sensor Circuit (Bank 1, Sensor 2)

P0137 -Low Voltage Output at O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)

P0138 -High Voltage Output at O2 Sensor Circuit (Bank 1, Sensor 2)

P0139 -O2 Sensor Circuit (Bank 1, Sensor 2) Slow Response

P0140 -O2 Sensor Circuit Not Working

P0141 -Faulty O2 Sensor Heater Circuit

P0142 -O2 Sensor Circuit (Bank 1 Sensor 3)

P0143 -Low Voltage Output at O2 Sensor Circuit (Bank 1 Sensor 3)

P0144 -High Voltage Output at O2 Sensor Circuit (Bank 1 Sensor 3)

P0145 -O2 Sensor Circuit (Bank 1 Sensor 3) Slow Response

P0146 -O2 Sensor Circuit (Bank 1 Sensor 3) Not Responding

P0147 -O2 Sensor Heater Circuit (Bank 1 Sensor 3) Malfunction

P0148 -Fuel pressure is Too Low or High

P0149 -Problem in the Fuel Timing Sequence

P0150 -O2 Sensor Circuit Sensor 1 Bank 2 Malfunction

P0151 -Low Voltage Output at O2 Sensor Circuit Sensor 1 Bank 2

P0161 – It tells you that there’s a sensor malfunction in bank 2 sensor 2. It’s typically followed by the Check Engine Light.

P0171 – The air-fuel ratio is not correct

P0172 – Fuel System Too Rich (Bank 1)

P0234 – Turbocharger/Supercharger “A” Overboost Condition

P0299 – Turbo or supercharger not performing well

P0300 – The P0300 OBD2 code denotes there is the engine is misfiring.

P0316 – The P0316 OBD2 code shows an engine misfire on startup.

P0340 – The P0340 OBD2 code indicates there’s an issue with your vehicle’s camshaft position sensor.

P0341 – Camshaft Position Sensor “A” Circuit Range/Performance (Bank 1 or Single Sensor)

P0335 – Crankshaft Position “A” Circuit MalfunctionP0335 – Crankshaft Position “A” Circuit Malfunction

P0440 – The code tells you there is a malfunction in your EVAP system, and is normally very easy to fix.

P0401 – It denotes the EGR system isn’t redirecting carbon dioxide to your engine as needed.

P0442 – The error code shows a small leak in your EVAP system.

P0455 – The fault code indicates there’s a leak in your EVAP system.

P0446 – It tells you there is a problem with the EVAP vent control circuit.

P0452 – The code means low pressure in your EVAP system.

P0456 – The code means there is a leak in your EVAP system.

P0504 – Brake Switch “A”/”B” Correlation

P0611 – Fuel Injector Control Module Performance is down

P0700 – It indicates a potentially serious issue with your transmission control system.

P0733 – Issues with the shifting into 3rd gear

P2047 – Reductant Injection Valve Circuit/Open issue

P2074 – Throttle Position Correlation at Higher Load- Manifold Absolute Pressure/Mass Air Flow

P2092 – “A” Camshaft Position Actuator Control Circuit Low

P2148 – Fuel Injector Group “A” Supply Voltage Circuit High

P2209 – Nox Sensor Heater Sense Circuit Range/Performance

P2188 – System Too Rich at Idle Bank 1

P2299 – The brake Pedal Position is not correct

P2257 – Secondary Air Injection System Control “A” Circuit Low

P2448 – Secondary Air Injection System High Air Flow Bank 1

P242B – Fix Exhaust Gas Temperature Sensor Circuit Range/Performance Bank 1 Sensor 3

P246F – Exhaust gas temperature sensor bank 1 sensor 4

P06DE – Engine oil pressure control circuit stuck on

P012B – Turbocharger/supercharger inlet pressure sensor issue

A detailed review of OBD2 Codes with their signs, causes, and diagnostic procedure

Popular Powertrain (P) OBD2 Codes

P0008

Code Description:

Engine Position System Performance – Bank 1

Interpretation:

Bank 1 camshaft and the crankshaft have a variation in mechanical timing. This implies that the engine control module (ECM) is having timing problems.

Key Signs:

Check Engine Light comes on
Reduced power
Rough acceleration
Lower fuel economy

Potential Causes:

Timing chain is experiencing tension
Timing chain is stretched
Crankshaft reluctor wheel is not referenced to TDC (top dead center)
Wiring damage
Worn out timing parts
Internal damage to ECM

Diagnostic Procedure:

Apply a sophisticated code reader to pull engine codes
Inspect the VCT/VVT circuit for open/damaged wires.

P0010

Code Description:

Intake Camshaft Position Actuator Circuit / Open (Bank 1)

Interpretation:

Bank 1 camshaft and the crankshaft have a variation in mechanical timing. The issue takes place when the engine undergoes high RPM. The ECM doesn’t properly adjust valve lift at high RPM.

Key Signs:

Check Engine Light comes on
The engine performs badly at high RPM
Vehicle runs roughly
Lower fuel economy
Vehicle doesn’t pass emission test

Potential Causes:

Sludge in engine oil
Faulty OVC (oil control valve)
Internal damage to ECM
ECM timing is out of sync
Wiring damage
Malfunction of crankshaft or camshaft sensor
A short in VCT/VVT circuit, or the circuit is open

Diagnostic Procedure:

Use an advanced diagnostic tool to pull engine codes
Inspect the VVT/VCT solenoid system for dirty oil
Inspect the circuit for wiring problems

P0011

Code Description:

Intake Camshaft Position Timing – Over-Advanced (Bank 1)

Interpretation:

The camshaft timing for bank 1 is over the limit set by the ECM. This leads to an over-advanced condition that happens either during retarding or advancing of the camshaft timing

Related article: Step-By-Step Guide on How to read OBD1 Codes

Key Signs:

Check Engine Light comes on
Hard starting
Poor idle
Car may run rough or stall
Poor fuel economy
Car may fail the emission test

Potential Causes:

Camshaft remains advanced despite ECM commanding it to retard
Bank 1 oil control solenoid may be clogged or stuck
Oil may be too thick and is thus blocking passages in bank 1
Wiring issues in VCT/VVT
Oil continuously flows to VCT piston chamber

Diagnostic Procedure:

Confirm that engine oil is clean and has the recommended viscosity
Visually inspect the wiring in the CVT system
Pull engine codes and live data with the help of an advanced diagnostic scanner

P0012

Code Description:

Intake Camshaft Position Timing – Over-Retarded (Bank 1)

Interpretation:

Bank 1 is having an over-retarded timing condition that occurs either during retarding or advancing

Key Signs:

Check Engine Light comes on
Rough start
Poor fuel economy
Vehicle may run rough or stall
Vehicle may fail the emission test

Potential Causes:

Camshaft timing is wrong
Wiring issues in VCT/VVT
Oil continuously flows to VCT piston chamber
Timing valve solenoid control has failed and is stuck in the open position
Oil may be extremely thick and is blocking passages in bank 1

Diagnostic Procedure:

Check that engine oil is clean
Inspect the wiring in the CVT system
Pull engine codes and live data using an advanced diagnostic scan tool
With the help of a bidirectional scan tool, instruct the timing valve solenoid control valve to open and close then see if camshaft timings change. If they change it means the valve is not the issue.

P0014

Code Description:

Exhaust Camshaft Position Timing – Over-Advanced (Bank 1)

Interpretation:

Bank 1 camshaft is having an over-advanced timing condition that occurs either during retarding or advancing

Key Signs:

Check Engine Light comes on
Rough start
Bad fuel economy
Vehicle may run rough or stall
Vehicle may fail the emission test

Potential Causes:

Camshaft timing is wrong
Wiring issues in VCT/VVT
Oil continuously flows to VCT piston chamber
Timing valve solenoid control has failed and is stuck in the open position
Oil may be extremely thick and is blocking passages in bank 1

Diagnostic Procedure:

Confirm that engine oil is clean and full in the tank
Inspect the wiring in the CVT system
Pull engine codes and live data with the help of a high-end diagnostic scan tool
With the help of a bidirectional scan tool, instruct the timing valve solenoid control valve to open and close then see if camshaft timings change. If they change it means the valve is not the issue.

P0016

Code Description:

Crankshaft Position Camshaft Position Correlation Bank 1 Sensor A

Interpretation:

The crankshaft and camshaft signals are out of time. This indicates that the ECM can detect that the timing of the crankshaft and that of the camshaft do not correlate.

Key Signs:

Check Engine Light comes on
The engine may crank but fail to start
The engine may proceed to run but it will record poor performance
There is a rattling sound in the harmonic balancer
Poor fuel economy

Potential Causes:

The timing chain is overstretched
Tone ring on the camshaft and/or crankshaft is has slipped or broken
Timing chain has jumped teeth and placed the camshaft timing out of position
Issues with camshaft phaser and putting the phaser out of position
Wiring to crank/cam sensor is damaged

Diagnostic Procedure:

Check oil control valve (OCV) for connection or wiring issues
Inspect that engine oil is clean, full and has the right viscosity
Pull engine codes and live data using a high-end diagnostic scanner
Utilize a bidirectional scan tool, instruct the OVC on and off then observe if camshaft timings change. If they change it means the valve is not the issue.

P0021

Code Description:

Intake Camshaft Position Timing – Over-Advanced (Bank 2)

Meaning:

The camshaft timing for bank 2 is over the limit put down by the ECM. This leads to an over-advanced condition that happens either during retarding or advancing the camshaft timing.

Key Signs:

Check Engine Light comes on
It is hard starting
Poor idle
Vehicle may run rough or stall
Bad fuel economy
The vehicle may fail the emission test

Potential Causes:

Camshaft remains advanced despite ECM commanding it to retard
Bank 2 oil control solenoid may be clogged or stuck
Oil may be too thick and is thus blocking passages in bank 2
Wiring issues in VCT/VVT
Oil continuously flows to VCT piston chamber

Diagnostic Procedure:

Inspect that engine oil is clean and has the ideal viscosity
Check the wiring in the CVT system
Pull engine codes and live data with the assistance of an advanced diagnostic scanner

P0022

Code Description:

“A” camshaft position – timing over-retarded (Bank 2)

Interpretation:

The camshaft timing for bank 2 is over-retarded

Key Signs:

Check Engine Light comes on
Vehicle stalls
It hard starts

Potential Causes:

Camshaft remains retarded regardless of the ECM instructing it to advance
Wiring issues in VCT/VVT
Oil continuously flows to VCT piston chamber
Timing valve controlled solenoid has failed and stays open

Diagnostic Procedure:

Inspect the wiring in the CVT system
Pull engine codes and live data with the help of an advanced diagnostic code reader
Reset the codes. If P0022 returns use a bidirectional scanner to verify whether VCT solenoid is functioning.

P0030

Code Description:

Heated Oxygen Sensor (H02S) Heater Control Circuit Bank 1 Sensor 1

Interpretation:

Bank 1, sensor 1 of the O2 sensor heater circuit is faulty. This indicates that the engine isn’t achieving closed-loop and thus the vehicle has increased emissions.

Key Signs:

Check Engine Light comes on
More time needed to achieve closed-loop
Poor fuel economy
The engine may go into the fixed fuel mix

Potential Causes:

H02S sensor in bank 1, circuit 1 is not sending the right signal to ECM
Defective or failed element in the heater circuit
Open in O2 sensor heater’s circuit
Open/short in O2 sensor heater’s battery
Faulty ECM

Diagnostic Procedure:

Check the wiring and power to the O2 sensor and make sure there’s no damage/open/short
Apply scan tool to pull engine codes
Inspect voltage of O2 sensor and make sure it corresponds manufacturer’s specs
Replace O2 sensor if need be

P0031

Code Description:

Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 1 Sensor 1

Interpretation:

The resistance of the heater circuit in bank 1 is very low to heat fuel until it attains air to fuel ratio of 14:7. The fault is coming from the 1st sensor of bank 1. This code occurs when the resistance level is below 0.8A.

Key Signs:

Check Engine Light comes on
This is rare, but ECM may enter failsafe mode

Potential Causes:

Short or open in the O2 heater circuit
Bad O2 sensor heater
A wiring issue in the circuit leading to the heater. It may be broken or frayed
Bad ECM

Diagnostic Procedure:

Check wiring and power to the O2 sensor and make sure there’s no damage/open/short
Utilize a scan tool to pull engine codes

P0037

Code Description:

Heated Oxygen Sensor (H02S) Heater Control Circuit Bank 1 Sensor 2

Interpretation:

Bank 1, sensor 2 of the O2 sensor heater circuit is defective. Thus, the engine isn’t achieving closed loop and as a result, the vehicle has increased emissions.

Key Signs:

Check Engine Light comes on
More time needed to achieve closed loop
Reduced fuel economy
The engine may go into the fixed fuel mix

Potential Causes:

H02S sensor in bank 1, circuit 2 is not sending the correct signal to ECM
Faulty or failed element in the heater circuit
Open in O2 sensor heater’s circuit
Open/short in O2 sensor heater’s battery
Bad ECM

Diagnostic Procedure:

Check the wiring and power to the O2 sensor and ensure there’s no damage/open/short
Pull engine codes using a scanner
Inspect voltage of O2 sensor and ensure it corresponds with manufacturer’s specs
Change O2 sensor if needed

P0087

Code Description:

Fuel Rail/System Pressure – Too Low

Interpretation:

The ECM has indicated that the pressure of fuel going to the fuel pump module is below the pressure that was instructed by the ECM

Key Signs:

Check Engine Light comes on
Vehicle may have a rich fuel condition
The vehicle may also misfire
Vehicle may operate poorly

Potential Causes:

Clogged fuel filter or fuel screen
Defective fuel pressure sensor
Defective fuel pump
Fault in the fuel line that’s causing a restriction

Diagnostic Procedure:

Use code reader to pull engine codes
Visually inspect the fuel tank, fuel filter, and fuel lines
Take manual readings of fuel pressure and compare with specifications
Run a fuel pump test

P0102

Code Description:

Mass or Volume Air Flow Circuit Low Input

Interpretation:

The mass airflow (MAF) sensor is not working within the normal expectation and is thus sending a lower signal than normal (due to low voltage)

Key Signs:

Check Engine Light comes on
Extremely low fuel consumption and thus internal engine problems
The engine runs roughly
Car idles and stalls often

Potential Causes:

Faulty MAF sensor
Presence of dirt and debris in MAF (restricts airflow)
Leaks in the air intake system
Poor wiring of the circuit to MAF sensor

Diagnostic Procedure:

Apply scanner to pull engine codes
Inspect the MAF sensor wiring and circuit
Check for air leaks in the air intake system
Check MAF to view if there’s dirt and debris

P0106

Code Description:

Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem

Interpretation:

The Powertrain Control Module (PCM) has not found a change in engine speed, throttle angle, and/or exhaust gas recirculation (EGR) despite a rise in manifold absolute pressure (MAP). An increase in MAP shows an increase in engine load.

Key Signs:

Check Engine Light comes on
Poor fuel economy
The engine fails to idle
The engine produces black smoke (visible at tailpipe)
It has the erratic acceleration

Potential Causes:

Defective MAP sensor
The air intake part is loose, cracked or doesn’t have its plastic fitting
Water or dirt affecting connector to MAP sensor
Corrosion may be leading to poor signal to and from MAP sensor
A defective PCM

Diagnostic Procedure:

Apply an advanced scan tool to pull engine codes
Use a scanner to read the MAP sensor when the engine is off but the key is on. It should be similar or close to barometric pressure (BARO) reading.
Turn on the engine and see if the MAP sensor readings drop significantly. If it does, then the sensor is working well.

P0107

Code Description:

Manifold Absolute Pressure/Barometric Pressure Circuit Low Input

Interpretation:

PCM has discovered that the voltage in the MAP sensor is less than .25 volts, which is too low to send a dependable signal.

Key Signs:

Check Engine Light comes on
Car is hard to start
Bad fuel economy
Engine fails to idle
The engine produces black smoke (cab be seen at tailpipe)
Engine cranks for long
Erratic acceleration

Potential Causes:

Faulty MAP sensor
Open or short in the signal circuit, 5volt reference circuit or ground circuit
PCM is defective (least likely but not unlikely)

Diagnostic Procedure:

Apply a high-end scanner to pull engine codes
Use a diagnostic scan tool to take the voltage of the MAP sensor when the engine is on and the key is on. If it’s less than 0.5V, turn the engine off, remove the MAP sensor and use a volt/ohm meter to detect for 5 volts on the 5-volt reference circuit

P0108

Code Description:

Manifold Absolute Pressure/Barometric Pressure Circuit High Input

Interpretation:

It means that the PCM has discovered that the voltage in the MAP sensor is more than 5 volts or generally greater than commanded under the prevailing situation.

Key Signs:

Check Engine Light comes on
Bad fuel economy
Engine fails to idle and may not start completely
The engine produces black smoke (it can be seen at tailpipe)
The engine cranks for long
Erratic acceleration

Potential Causes:

Defective MAP sensor
Open or short in the signal circuit, 5volt reference circuit or ground circuit
Leak in vacuum system, more so in the engine or supply line to MAP sensor
Bad PCM

Diagnostic Procedure:

Utilize a high-end automotive scan tool to pull engine codes
Use an advanced scanner to take the reading of the MAP sensor when the engine is off but the key is on. It should be similar or close to barometric pressure (BARO) reading
If the difference between the two readings is more than 0.5 then you’re looking at a faulty MAP sensor.

P0113

Code Description:

Intake Air Temperature Circuit High Input

Interpretation:

The PCM has identified that the signal voltage from the intake air temperature (IAT) is more than 5V, which is more than the expected range.

Key Signs:

Check Engine Light comes on
The engine may run extra lean

Potential Causes:

Faulty IAT sensor
Defective or loose wiring at IAT sensor
Open or short in IAT ground circuit, signal circuit or reference circuit
PCM is faulty

Diagnostic Procedure:

Apply an advanced scan tool to pull engine codes.
Check live data from the IAT sensor. If the reading is less than -30 degrees then the sensor is likely to be defective. And if not, then it’s probably an intermittent issue.
Inspect the wiring for opens and loose connections

P0116

Code Description:

Engine Coolant Temperature Circuit Range/Performance Problem

Interpretation:

The PCM has seen an abrupt and quick change in engine coolant temperature (ECT) at a period when there shouldn’t be such a change.

Key Signs:

Check Engine Light comes on
Low fuel economy
The engine refuses to idle and may not start at all
The engine produces black smoke (visible at tailpipe)

Potential Causes:

The thermostat is either missing or open
A bad ECT sensor
Open or short in ECT signal or ground circuit

Diagnostic Procedure:

With the help of an OBD2 scanner, commence by diagnosing and resetting any other ECT codes
Then, view the ECT reading. When the engine is cold the reading should match ambient temperature reading. If it doesn’t then there’s an issue with the ECT sensor

P0118

Code Description:

Engine Coolant Temperature Circuit High Input

Interpretation:

The PCM has identified that ECT is less than freezing temp yet the engine has been running for several minutes, which is not normal.

Key Signs:

Check Engine Light comes on
Bad fuel economy
Engine fails to idle and may not start at all
The engine produces black smoke (visible at tailpipe)

Potential Causes:

Defective ECT sensor
Open or short in ECT signal or ground circuit
PCM is defective

Diagnostic Procedure:

Utilize an OBD2 scan tool, check the reading of ECT. If it’s a logical reading then the issue is intermittent.
Conduct a wiggle test while looking out for drop-outs. If there are any then there’s a poor connection to or from the ECT sensor

P0121

Code Description:

Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance Problem

Interpretation:

The PCM has discovered that the throttle position sensor (TPS) voltage is more or less than it should be for the present RPM.

Key Signs:

Check Engine Light comes on
The vehicle produces black smoke (visible at tailpipe)
Vehicle stumbles when you accelerate or decelerate
The engine may fail to start totally

Potential Causes:

Faulty TPS
Open or short in TPS circuit
Bad connection to TPS
PCM is bad

Diagnostic Steps:

Inspect all wiring to TPS for loose, open or short connections
Apply an OBD2 scanner, view for live, and freeze frame data from TPS. If it doesn’t read 0.5 at idle and 4.5 at full throttle the TPS is bad

P0122

Code Description:

Throttle/Pedal Position Sensor/Switch A Circuit Low Input

Meaning:

PCM is reporting that the TPS has recorded a voltage that is lower than the normal minimum limit. The value varies from one car to another but the code may come when the voltage hits .20V or less

Check Engine Light comes on
Extremely high idle
Rough or low idle
The vehicle stalls
Acceleration is poor or low

Potential Causes:

Defective TPS
OBD port not working
Open or short in TPS circuit
Wrong mounting of TPS after replacement
TPS has loosened
A defective PCM

Diagnostic Procedure:

Visually inspect all wiring to TPS for loose, open or short connections
Confirm that TPS is tightly in position, especially if you recently changed it

P0123

Code Description:

Throttle/Pedal Position Sensor/Switch A Circuit High Input

Interpretation:

The PCM is reporting that the TPS has registered a voltage that is higher than the usual /maximum limit, which is normally around 5 volts.

Key Signs:

Check Engine Light comes on
Extremely high idle
Rough or low idle
Frequent surges

Possible Causes:

Defective TPS
Open or short in TPS circuit
Poor installation of the TPS after replacement
PCM is defective (least likely but not unlikely)

Diagnostic Procedure:

Check all wiring to TPS for loose, open or short connections
The view that TPS is firmly held in position, especially if you recently replaced it

P0128

Code Description:

Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)

Interpretation:

The PCM has discovered that the engine has not attained the required temperature despite being on for enough time to attain that temperature.

Key Signs:

Check Engine Light may turn on
The engine temp drops when the car is in high speed
The engine takes abnormally long to warm

Potential Causes:

The thermostat is leaking or stuck in the open position
The engine coolant level is too low
Defective IAT sensor
Bad ECT sensor
Faulty cooling fan

Diagnostic Procedure:

Inspect whether coolant strength and level are in the suggested range
Find out whether IAT sensor, ECT sensor, and coolant fan are functioning
If all the above are okay then the thermostat is the one with an issue

P0130

Code Description:

O2 Sensor Circuit Malfunction (Bank 1 Sensor 1)

Interpretation:

The ECM has discovered that the O2 sensor voltage stayed lower than normal (below .4v) for too long (20 seconds or more)

Key Signs:

Check Engine Light turns on
The vehicle produces black smoke (visible at tailpipe)
Low fuel economy
Engine may fail to start totally
When the engine starts it may run rough or stumble

Potential Causes:

Normally connected to corrosion, loose terminal or burnt wire in the O2 sensor connector
Faulty O2 sensor
Open or short in the wiring to the O2 sensor
Unmetered oxygen is getting back into exhaust system, mainly because there are holes in the system

Diagnostic Procedure:

Check all the wiring to O2 sensor for loose, open or short connections
Conduct a wiggle test to know where the voltage drops out
Utilize an OBD2 diagnostic scanner, inspect whether sensor 1 of bank 1 is switching well. Usually it should switch evenly between rich and lean in quick successions.

P0131

Code Description:

O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)

Interpretation:

The ECM has discovered that there’s a low voltage condition in bank 1 sensor 1; i.e. O2 sensor voltage remained too low for longer than 2 minutes.

Key Signs:

Check Engine Light turns on
The vehicle produces black smoke (visible at tailpipe)
Bad fuel economy
The engine may fail to start totally
The engine starts but it may run rough and/or stumble

Potential Causes:

Normally, this is connected to corrosion, loose terminal or burnt wire in the O2 sensor 1 connector
Faulty O2 sensor
Open or short in the wiring to the O2 sensor
O2 circuit is undergoing high resistance

Diagnostic Procedure:

Check all wiring to O2 sensor 1 for loose, open or short connections
Apply a wiggle test to know where the voltage drops out
Utilize an OBD2 scan tool, inspect whether sensor 1 of bank 1 is switching well.

P0132

Code Description:

O2 Sensor Circuit High Voltage (Bank 1 Sensor 1)

Interpretation:

The heated O2 sensor in bank 1 sensor 1 is providing a higher voltage reading than it is required. For most cars the code comes when a voltage that exceeds 1.5V.

Key Signs:

Typically, it doesn’t feature signs. Nevertheless, in a few cases the Check Engine Light may come on and fuel economy may be poor.

Potential Causes:

Fuel temp is very high
Short, open or broken wire in O2 sensor circuit

Diagnostic Procedure:

Check all the wiring to O2 sensor for loose, open or short connections
Perform a wiggle test to know where the voltage drops out
Using an OBD2 diagnostic scanner, inspect whether sensor 1 of bank 1 is switching properly.

P0133

Code Description:

O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)

Interpretation:

The O2 sensor or ECM can’t adjust air to fuel ratio as it’s required to even when the engine is operating

Key Signs:

Also, this code doesn’t come with signs. However, you may see a Check Engine Light come on and fuel economy may become poor.

Potential Causes:

A faulty first O2 sensor in bank 1
Short, open or broken wire in the O2 sensor circuit
An exhaust leak

Diagnostic Procedure:

Check all the wiring to first O2 sensor for loose, open or short connections
Utilize a wiggle test to know where the voltage drops out
Inspect if there are exhaust leaks or air inlet leaks
Use an OBD2 scanner to inspect whether sensor 1 of bank 1 is switching well.

P0134

Code Description:

O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)

Interpretation:

The PCM has concluded that the first O2 sensor in bank 1 is inactive or open because it has not warmed up after more than 1 minute of the engine running.

Key Signs:

Check Engine Light turns on
The vehicle produces black smoke (visible at tailpipe)
Bad fuel economy
The engine may run rough and/or stumble

Potential Causes:

Defective O2 sensor
Short, open or broken wire in the O2 sensor circuit
Exhaust leak
Bad heater circuit in the O2 sensor
The heater circuit has blown fuse
The PCM is faulty

Diagnostic Procedure:

Check all the wiring to first O2 sensor (bank 1) for loose, open or short connections
Conduct a wiggle test to find out where the voltage drops out
Check whether there are exhaust leaks or air inlet leaks

P0135

Code Description:

O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

Interpretation:

In most cases, when the O2 heater attains operating temperature, O2 sensor adjusts based on ambient temp. If ECM shows that the O2 sensor took too long to adjust this code is set. It applies to the first sensor of bank 1.

Key Signs:

Check Engine Light comes on
Lower fuel economy

Potential Causes:

Short, open or broken wire in O2 heating system
Great resistance in O2 heater element or circuit

Diagnostic Procedure:

Inspect all the wiring to first O2 sensor (bank 1) for loose, open or short connections
Perform a wiggle test to find out where the voltage drops out
If the code is relentless change the O2 sensor or use an Autel Maxidiag Elite MD802 scanner

P0136

Code Description:

O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)

Interpretation:

The ECM has indicated that there’s a low voltage condition in bank 1 sensor 2; i.e. O2 sensor voltage remained too low for longer than 2 minutes.

Key Signs:

Check Engine Light comes on
The vehicle produces black smoke (visible at the tailpipe)
Bad fuel economy
The engine may fail to start totally
In case it starts it may run rough and/or stumble

Potential Causes:

It is usually a problem connected to corrosion, loose terminal, or burnt wire in the O2 sensor 2 connectors.
Bad O2 sensor
Open or short in the wiring to the O2 sensor
The O2 circuit is undergoing great resistance

Diagnostic Procedure:

Inspect all the wiring to O2 sensor 2 for loose, open or short connections
Apply a wiggle test to know where the voltage drops out
Use an OBD2 scanner to detect whether sensor 2 of bank 1 is switching properly.

P0137

Code Description:

O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)

Interpretation:

The PCM has detected that the O2 sensor may be inactive

Key Signs:

It usually lacks symptoms. Nevertheless, you may see the Check Engine Light come on and fuel economy may reduce drastically.

Potential Causes:

Defective O2 sensor
Short, open or broken wire in the O2 sensor circuit
Bad heater circuit in the O2 sensor
Great resistance in O2 heater element or circuit
Defective fuel pump regulator leading to very high or very low fuel pressure
There is an exhaust leak

Diagnostic Procedure:

Visually check all wiring to O2 sensor for loose, open or short connections
Conduct a wiggle test to detect where the voltage drops out
View whether exhaust leaks or air inlet leaks
If the code is relentless change the O2 sensor

P0138

Code Description:

O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)

Interpretation:

The heated O2 sensor in bank 1 sensor 2 is delivering a higher voltage reading than it should. Many vehicles show this code when the voltage exceeds 1.5V.

Key Signs:

Typically, it doesn’t come with signs. Nevertheless, signs like the Check Engine Light and lower fuel economy may show up.

Potential Causes:

Fuel temp is extremely high
Short, open or broken wire in the O2 sensor circuit

Diagnostic Procedure:

Check all the wiring to O2 sensor for loose, open or short connections
Apply a wiggle test to determine where the voltage drops out
Use an OBD2 scan tool to find out whether sensor 1 of bank 2 is switching as needed.

P0139

Code Description:

O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)

Interpretation:

The O2 sensor or ECM can’t change the air to fuel ratio as it’s supposed to even when the engine is running.

Key Signs:

Normally, it doesn’t come with signs. Nevertheless, signs like the Check Engine Light and lower fuel economy may show up.

Potential Causes:

The second O2 sensor in bank 1 is defective
Short, open or broken wire in the O2 sensor circuit
There is an exhaust leak

Diagnostic Procedure:

Inspect all the wiring to second O2 sensor for loose, open or short connections
Conduct a wiggle test to know where the voltage drops out
Inspect for exhaust leaks or air inlet leaks
With the help of an OBD2 scanner, verify whether sensor 2 of bank 1 is switching properly.

P0140

Code Description:

O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 2)

Interpretation:

The PCM has detected that the second O2 sensor in bank 2 is inactive or open because it has not warmed up after more than 1 minute of the engine running.

Key Signs:

Check Engine Light turns on
The vehicle produces black smoke (visible at tailpipe)
Bad fuel economy
The engine may run rough and/or stumble

Potential Causes:

Defective O2 sensor
Short, open or broken wire in the O2 sensor circuit
There is an exhaust leak
Bad heater circuit in the O2 sensor
The heater circuit has blown fuse
A faulty PCM

Diagnostic Procedure:

Inspect all the wiring to second O2 sensor (in bank 2) for loose, open or short connections
Perform a wiggle test to know where the voltage drops out
Check for exhaust leaks or air inlet leaks

P0141

Code Description:

O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

Interpretation:

The moment the O2 heater attains operating temperature, O2 sensor switches based on ambient temp. If ECM indicates that the O2 sensor took too long to switch this code is set. It applies to the second sensor of bank 1.

Key Signs:

Check Engine Light comes on
Low fuel economy

Potential Causes:

Short, open or broken wire in O2 heating system
High resistance in O2 heater element or circuit

Diagnostic Procedure:

Verify all the wiring to second O2 sensor (bank 1) for loose, open or short connections
Perform a wiggle test to know where the voltage drops out
If the code is lasting replace the O2 sensor

P0151

Code Description:

O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)

Interpretation:

It shows the ECM has detected that there’s a low voltage situation in bank 2 sensor 1; i.e. O2 sensor voltage remained too low for longer than 2 minutes.

Key Signs:

Check Engine Light comes on
The vehicle produces black smoke
Bad fuel economy
The engine may fail to start completely
The car may run rough and/or stumble if it starts

Potential Causes:

Normally an issue connected to corrosion, loose terminal or burnt wire in the O2 sensor 2 connector
Faulty O2 sensor
Open or short in the wiring to the O2 sensor
The O2 circuit is going through the high resistance

Diagnostic Procedure:

Check all the wiring to O2 sensor 1 for loose, open or short connections
Perform a wiggle test to detect where the voltage drops out
Utilize an OBD2 scan tool to inspect whether sensor 1 of bank 2 is switching properly.

P0153

Code Description:

O2 Sensor Circuit Slow Response (Bank 2 Sensor 1)

Interpretation:

The O2 sensor or ECM can’t change the air to fuel ratio as it’s supposed to even when the engine is running

Key Signs:

Check Engine Light may come on and
Poor fuel economy

Potential Causes:

First O2 sensor in bank 2 is faulty
Short, open or broken wire in the O2 sensor circuit
Exhaust leak

Diagnostic Procedure:

Investigate all the wiring to second O2 sensor for loose, open or short connections
Conduct a wiggle test to detect where the voltage drops out
Inspect for exhaust leaks or air inlet leaks
Utilize an OBD2 scan tool to investigate whether sensor 1 of bank 2 is switching properly.

P0154

Code Description:

O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 1)

Interpretation:

The PCM has shown that first O2 sensor in bank 2 is inactive or open because it has not warmed up after more than 1 minute of the engine running

Key Signs:

Check Engine Light comes on
The car emits black smoke
Bad fuel economy
The engine may run rough and/or stumble

Potential Causes:

Bad O2 sensor
Short, open or broken wire in the O2 sensor circuit
There exhaust leak
Faulty heater circuit in the O2 sensor
The heater circuit has blown fuse
The PCM is bad

Diagnostic Procedure:

Check all the wiring to first O2 sensor (bank 2) for loose, open or short connections
Apply a wiggle test to determine where the voltage drops out
Check for exhaust leaks or air inlet leaks

P0157

Code Description:

O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)

Interpretation:

The ECM has investigated that there’s a low voltage condition in bank 2 sensor 2; i.e. O2 sensor voltage remained too low for longer than 2 minutes

Key Signs:

Check Engine Light turn on
The car emits black smoke
Low fuel economy
The engine may fail to start totally
The engine may run rough and/or stumble if it starts

Potential Causes:

It is an issue normally linked to corrosion, loose terminal or burnt wire in the O2 sensor 2 connector
Faulty O2 sensor
Open or short in the wiring to the O2 sensor
The O2 circuit is going through a high resistance

Diagnostic Procedure:

Investigate all the wiring to O2 sensor 2 for loose, open or short connections
Perform a wiggle test to find out where the voltage drops out
Use a diagnostic scan tool to check whether sensor 2 of bank 2 is switching well.

P0161

Code Description:

O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)

Interpretation:

If the O2 heater attains operating temperature, O2 sensor switches based on ambient temp. If ECM finds out that the O2 sensor took too long to switch this code is set. It applies to the second sensor of bank 2.

Key Signs:

Check Engine Light turns on
Lower fuel economy

Potential Causes:

Short, open or broken wire in O2 heating system
Great resistance in O2 heater element or circuit

Diagnostic Procedure:

Inspect all the wiring to second O2 sensor (bank 2) for loose, open or short connections
Utilize a wiggle test to know where the voltage drops out
If the code is lasting change the O2 sensor

P0171

Code Description:

System Too Lean (Bank 1)

Interpretation:

There’s a lean condition in bank 1; i.e. there’s excess oxygen in the exhaust

Key Signs:

The decrease in engine power
The vehicle hesitates then surges when accelerated
It is rough idle

Potential Causes:

Bad or defective MAF sensor
MAF sensor has a vacuum leak
Positive Crankcase Ventilation (PCV) valve is stuck in an open position
A leakage either in PCV or vacuum system

Diagnostic Procedure:

Check MAF sensor in bank 1 for dirt and debris
Inspect whether fuel pressure is correct
Inspect vacuum and PCV for leaks
Perform a smog test using an OBD2 diagnostic scanner

P0172

Code Description:

System Too Rich (Bank 1)

Interpretation:

There’s a rich condition in bank 1; i.e. there’s too little oxygen in the exhaust

Key Signs:

Usually, it doesn’t come with signs. Nevertheless, signs like the Check Engine Light and lower fuel economy may show up.

Potential Causes:

Dirty or defective MAF sensor
MAF sensor has a vacuum leak
The problem relating to fuel pressure or delivery

Diagnostic Procedure:

Inspect MAF sensor in bank 1 for dirt and debris
Inspect whether fuel pressure is right
View fuel lines and injectors for any leaks/openings and dirt
Investigate vacuum, PCV and exhaust for leaks
Conduct a smog test using OBD2 scanner

P0174

Code Description:

System Too Lean (Bank 2)

Interpretation:

There’s a lean circumstance in bank 2; i.e. there’s excess oxygen in the exhaust

Key Signs:

Great decrease in engine power
Vehicle hesitates then increases when accelerated
Rough idle

Potential Causes:

Bad or defective MAF sensor
MAF sensor has a vacuum leak
Positive Crankcase Ventilation (PCV) valve is stuck in an open position
A leak either in PCV or vacuum system

Diagnostic Procedure:

Investigate MAF sensor in bank 2 for dirt and debris
Inspect whether fuel pressure is correct
View vacuum and PCV for leaks
Perform a smog test using OBD2 scanner

P0175

Code Description:

System Too Rich (Bank 2)

Interpretation:

There’s a rich condition in bank 2; i.e. there’s too little oxygen in the exhaust

Key Signs:

This code doesn’t come with signs. However, signs like the Check Engine Light and lower fuel economy may show up.

Potential Causes:

Filthy or defective MAF sensor
The MAF sensor has a vacuum leak
An issue relating to fuel pressure or delivery

Diagnostic Procedure:

Investigate MAF sensor in bank 2 for dirt and debris
Inspect whether fuel pressure is right
Check fuel lines and injectors for any leaks/openings and dirt
Inspect vacuum, PCV and exhaust for leaks
Conduct a smog test using OBD2 diagnostic scanner

P0193

Code Description:

Fuel Rail Pressure Sensor Circuit High Input

Interpretation:

The PCM has discovered that the pressure of fuel is not within the range that’s recommended by the car manufacturer.

Key Signs:

Check Engine Light comes on
The engine cranks but doesn’t start
Vehicle hesitates upon the increase of speed

Potential Causes:

Faulty fuel rail pressure (FRP) sensor
Bad fuel pump
Open or short in FRP circuit
Low or no fuel in the tank

Diagnostic Procedure:

Check all the wiring and connections in FRP circuit and check for shorts, opens, broken and melted wires
Inspect for corroded or burnt terminals in connectors
Apply a car scanner to pull codes and freeze frame data

P0300

Code Description:

Random/Multiple Cylinder Misfire Detected

Interpretation:

The PCM has identified that there’s an engine cylinder that’s not firing as needed. It could be one or more cylinders. The PCM hasn’t specified the exact cylinder.

Key Signs:

Check Engine Light turns on
Check Engine Light may flash
Engine lacks the required power
The engine may be difficult to start
The engine may stumble and hesitate often

Possible Causes:

Bad or worn out spark plugs
Low fuel pressure
Vacuum leak
Faulty catalytic converter
Faulty fuel injector
Bad coil
The faulty camshaft position sensor
Bad crankshaft sensor
Trouble with distributor

Diagnostic Steps:

Use a code reader to pull codes and view if there are any other besides P0300. Address the others first.
Check whether there are loose, open or short wires in ignition coils
Investigate whether spark plugs and their wires are in good condition
Inspect that fuel pressure is within the predetermined range
Check fuel injectors to view whether they are in good condition or not

P0301

Code Description:

Cylinder 1 Misfire Detected

Interpretation:

The PCM has discovered that cylinder #1 is not firing as required

Key Signs:

Check Engine Light comes on
Check Engine Light may flash
Engine lacks power
The engine may be troublesome to start
The engine may stumble and hesitate often

Potential Causes:

Bad or worn out spark plugs in cylinder 1
Low fuel pressure
Vacuum leak
Faulty catalytic converter
Bad fuel injector
Bad coil
The faulty camshaft position sensor
Bad crankshaft sensor
Problem with distributor

Diagnostic Procedure:

With the help of a scanner, pull codes, and view if there are any other besides P0301. Rectify the others first before moving forward.
Examine whether there are loose, open or short wires in ignition coils in cylinder 1
Check whether cylinder 1 spark plugs and their wires are in good condition
Test that fuel pressure is within the required range
Check fuel injectors to know whether they are in perfect state

P0302

Code Description:

Cylinder 2 Misfire Detected

Interpretation:

The PCM has discovered that cylinder #2 is not firing well

Key Signs:

Check Engine Light comes on
The engine lacks power
The engine may be hard to start
Check Engine Light may flash
The engine may stumble and hesitate often

Potential Causes:

Bad or worn out spark plugs in cylinder 2
Low fuel pressure
Vacuum leak
Faulty catalytic converter
Faulty fuel injector
Defective coil
The bad camshaft position sensor
Bad crankshaft sensor
Issue with distributor

Diagnostic Procedure:

Utilize a scan tool to pull codes and view if there are any other besides P0302. Address the others first
Examine whether there are loose, open or short wires in ignition coils in cylinder 2
Check whether cylinder 2 spark plugs and their wires are in good condition
Inspect that fuel pressure is within the suggested range
Examine fuel injectors to view whether they are in perfect state

P0303

Code Description:

Cylinder 3 Misfire Detected

Interpretation:

The PCM has discovered that cylinder #3 is not firing well

Key Signs:

Check Engine Light comes on
Engine lacks power
Check Engine Light may flash
The engine may be difficult to start
The engine may stumble and hesitate often

Potential Causes:

Bad or worn out spark plugs in cylinder 3
Low fuel pressure
Vacuum leak
Faulty catalytic converter
Bad fuel injector
Defective coil
The faulty camshaft position sensor
Bad crankshaft sensor
Issue with distributor

Diagnostic Procedure:

Utilize scanner to pull codes and view if there are any other besides P0303. Tackle the others first.
Examine whether there are loose, open or short wires in ignition coils in cylinder 3
Check whether cylinder 3 spark plugs and their wires are in perfect condition
Inspect that fuel pressure is within the predetermined range
Examine fuel injectors to know whether they are in good state

P0304

Code Description:

Cylinder 4 Misfire Detected

Interpretation:

The PCM has discovered that cylinder #4 is not firing as needed

Key Signs:

Check Engine Light comes on
Engine lacks power
Check Engine Light may flash
The engine may be hard to start
The engine may stumble and hesitate often

Potential Causes:

Bad or damaged spark plugs in cylinder 4
Low fuel pressure
There is a vacuum leak
Faulty catalytic converter
Defective fuel injector
Bad coil
The damaged camshaft position sensor
Faulty crankshaft sensor
Issue with distributor

Diagnostic Procedure:

Apply a scan tool to pull codes and determine if there are any other besides P0304. Handle the others first.
Check whether there are loose, open or short wires in ignition coils in cylinder 4
Examine whether cylinder 4 spark plugs and their wires are in good state
Inspect that fuel pressure is within the recommended range
Check fuel injectors to know whether they are in perfect state

P0305

Code Description:

Cylinder 5 Misfire Detected

Interpretation:

The PCM has determined that cylinder #5 is not firing as required

Key Signs:

Check Engine Light comes on
Engine lacks power
Check Engine Light may flash
The engine may be challenging to start
The engine may stumble and hesitate often

Potential Causes:

Worn out or defective spark plugs in cylinder 5
Low fuel pressure
Vacuum leak
Bad catalytic converter
Defective fuel injector
Worn out coil
The faulty camshaft position sensor
Bad crankshaft sensor
Problem with distributor

Diagnostic Procedure:

Utilize a scanner to pull codes and view if there are any other besides P0305. Rectify the others first.
Check whether there are loose, open or short wires in ignition coils in cylinder 5
Examine whether cylinder 5 spark plugs and their wires are in perfect condition
Inspect that fuel pressure is within the recommended range
Check fuel injectors to understand whether they are in excellent condition

P0306

Code Description:

Cylinder 6 Misfire Detected

Interpretation:

The PCM has determined that cylinder #6 is not firing well

Key Signs:

Check Engine Light comes on
Engine lacks power
Check Engine Light may flash
The engine may be difficult to start
The engine may stumble and hesitate regularly

Potential Causes:

Faulty or damaged spark plugs in cylinder 6
Low fuel pressure
A vacuum leak
Damaged catalytic converter
Faulty fuel injector
Bad coil
The defective camshaft position sensor
Faulty crankshaft sensor
Issue with distributor

Diagnostic Procedure:

Use a diagnostic scan tool to pull codes and view if there are any other besides P0306. Deal with the others first
Check whether there are loose, open or short wires in ignition coils in cylinder 6
Examine whether cylinder 6 spark plugs and their wires are in good state
Ensure that fuel pressure is within the recommended range
Check fuel injectors to see whether they are in excellent condition

P0316

Code Description:

Misfire Detected On Startup (First 1000 Revolutions)

Interpretation:

The PCM has figured out a misfire less than 1,000 revolutions after startup

Key Signs:

Check Engine Light comes on
The engine lacks power
It is rough idle

Potential Causes:

There is no fuel
Low fuel pressure
Damaged or worn-out spark plugs
Vacuum leak
Faulty catalytic converter
Faulty fuel injector
Bad coil
Damaged crankshaft sensor
Wiring defect in the crankshaft position sensor
Problem with PCM

Diagnostic Procedure:

Use a scanner to Pull all codes then address other misfire codes first
Examine all wiring and connectors in crankshaft and camshaft position sensors
Check freeze frame data to narrow down the issue

P0320

Code Description:

Ignition/Distributor Engine Speed Input Circuit Malfunction

Interpretation:

There’s electrical circuit damage in either the crankshaft position (CKP) sensor or camshaft position (CMP) sensor

Key Signs:

Check Engine Light comes on
The engine lacks power
The engine misfires, hesitates and stumbles
Engine cranks but it don’t start

Potential Causes:

Faulty ignition/distributor/engine speed sensor
Open or short in the power supply circuit and/or control circuit between PCM and ignition/distributor/engine speed sensor.

Diagnostic Procedure:

Examine all the connectors and wiring to ignition/distributor/engine speed sensors that are in excellent state.
Get rid of connectors and view if their terminals are burnt/corroded
Pull and reset the P0320 code, drive the vehicle for some minutes, and view if the code returns. If it does then there is a high chance a sensor requires replacing.

P0325

Code Description:

Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)

Interpretation:

The PCM has discovered that the engine’s knock sensor 1 in-circuit bank 1 is not functioning well

Key Signs:

Check Engine Light may turn on
The engine may also lose power

Possible Causes:

The first sensor in circuit bank 1 may be bad
Open or short in the wiring to the sensor
The issue with engine coolant
The engine is extremely lean
Defective PCM

Diagnostic Steps:

Check all the wiring to knock sensor 1 in-circuit bank 1. Make sure there are no shorts or open wires.
Examine coolant temp data to check problems
If there are no issues, get rid of the code and test drive the car. If it comes back the sensor is bad.

P0327

Code Description:

Knock Sensor 1 Circuit Low Input (Bank 1 or Single Sensor)

Interpretation:

The Knock sensor on bank 1 has low output voltage than required; normally 0.5V or less

Key Signs:

Check Engine Light may come on
Fluctuation in RPM and loss of engine power

Potential Causes:

The sensor in-circuit bank 1 may be defective
Open or short in the wiring to the sensor
Bad PCM

Diagnostic Procedure:

Inspect the resistance of the knock sensor and make sure it matches the manufacturer’s requirements.
Examine all the wiring to knock sensor 1 in-circuit bank 1. Make sure there are no shorts or open wires.
If the above procedures don’t work change the knock sensor

P0328

Code Description:

Knock Sensor 1 Circuit High Input (Bank 1 or Single Sensor)

Interpretation:

The Knock sensor on bank 1 has high output voltage than normal; typically 0.5V or less

Key Signs:

Check Engine Light turns on
Irregular RPM
The engine pings when accelerating
Loss of power
Knocking sound coming from the engine compartment

Possible Causes:

Knock sensor 1 in-circuit 1 may be faulty
Open or short in the wiring to the sensor
Low fuel pressure
Loose knock sensor
Utilizing the wrong type of fuel
Damaged PCM

Diagnostic Steps:

Make sure the right fuel was used
Check all the wiring to knock sensor 1 in-circuit bank 1. Make sure there are no shorts or open wires.
Examine the resistance of the sensor. If it doesn’t match manufacturer specs change the sensor

P0332

Code Description:

Knock Sensor 2 Circuit Low Input (Bank 2)

Interpretation:

The Knock sensor on bank 2 has low output voltage than required; normally 0.5V or less

Key Signs:

Check Engine Light may come on
Fluctuation in RPM and loss of engine power

Potential Causes:

The sensor in-circuit bank 2 may be bad
Open or short in the wiring to the sensor
Bad PCM

Diagnostic Procedure:

Inspect the resistance of the knock sensor and make sure it matches the manufacturer’s requirements.
Examine all the wiring to knock sensor 2 in-circuit bank 2. Ensure there are no shorts or open wires.
If the above doesn’t work change the knock sensor

P0335

Code Description:

Crankshaft Position Sensor A Circuit Malfunction

Interpretation:

The PCM has determined that the crankshaft position (CKP) sensor is not producing pulses or the pulses are not usual. It utilizes these pulses to know the position of the crankshaft.

Key Signs:

Check Engine Light comes on
The engine may fail to start
Car may run rough

Potential Causes:

Bad CKP sensor
Open or short in CKP sensor wiring
The timing belt is broken
Even though less likely, the PCM might fail

Diagnostic Procedure:

Commence by inspecting if there’s an RPM signal using a code reader
And if it’s not there, examine all the wires and connectors to the sensor. Repair if need be.
Inspect the sensor’s resistance and compare it with the manufacturer’s suggestions. If they don’t match change the sensor.

P0336

Code Description:

Crankshaft Position Sensor A Circuit Range/Performance

Interpretation:

The PCM has not obtained proper data from CKP sensor and thus cannot change ignition timing and fuel injection as required.

Key Signs:

Check Engine Light comes on
Intermittent stalling
The engine may fail to start
Irregular misfire

Potential Causes:

Worn out CKP sensor
Problem with CKP sensor wiring
Reluctor ring is dislodged from its stationary location
Reluctor ring is broken
Bad PCM

Diagnostic Procedure:

Check CKP sensor for wiring issues
Examine reluctor ring if it has broken/damaged teeth or dirt lodged in the teeth
Inspect sensor resistance and compare it with manufacturer suggestions. If they don’t match change the sensor

P0340

Code Description:

Camshaft Position Sensor Circuit Malfunction

Interpretation:

An issue in the camshaft position sensor (CPS) circuit. Therefore, PCM can’t perform ignition spark and fuel injector timing well.

Key Signs:

Check Engine Light turns on
The engine may fail to start
Car may run rough
Rough idle
There is misfire

Potential Causes:

Bad CPS
Open or short in CPS wiring
Faulty CKP sensor
A failed PCM

Diagnostic Procedure:

Check to wire to CPS and ensure there are no open or broken wires
Inspect CPS voltage if it’s within the manufacturer’s specs. If it’s not changed the sensor
Examine CKP sensor as well to detect whether it’s the source of the issue

P0341

Code Description:

Camshaft Position Sensor Circuit Range/Performance

Interpretation:

It shows that the signal the PCM is getting from the camshaft position sensor (CPS ) is inconsistent with what it should be.

Key Signs:

Check Engine Light may come on
Poor fuel economy

Potential Causes:

Faulty CPS
Open or short in CPS wiring
Bad reluctor wheel
Interference in CPS wiring (from spark plug)

Diagnostic Procedure:

Examine wiring to CPS and make sure there are no open or broken wires
Check reluctor wheel and examine for fault or missing teeth
Change the CPS

P0345

Code Description:

Camshaft Position Sensor A Circuit Malfunction (Bank 2)

Interpretation:

The PCM has determined an issue in the CPS circuit of bank 2. The issue could be anywhere in the circuit; sensor, wring, or PC.

Key Signs:

Check Engine Light comes on
Low engine power
Difficulty starting or no starting totally
Car runs rough and/or misfires

Potential Causes:

Open, grounded or short wiring in CPS circuit of bank 2
Faulty CPS
Bad CKP sensor

Diagnostic Procedure:

Check wiring to CPS in bank 2 and confirm there are no open or broken wires
Examine CPS voltage to ascertain it’s within the range specified by the manufacturer
Check circuit connectors for corrosion and burns
Examine that CKP sensor is operating as it should
Change CPS if all the above don’t work

P0351

Code Description:

Ignition Coil A Primary/Secondary Circuit Malfunction

Interpretation:

It indicates that there’s a short in the driver circuit for the engine’s coil #1 (the coil for cylinder #1)

Key Signs:

Check Engine Light comes on
There is an engine misfire

Potential Causes:

Short or open in the coil on plug (COP) driver circuit
Loose or broken connection at the coil
Bad COP
Faulty or failed PCM

Diagnostic Procedure:

If the engine is not misfiring, then it’s an intermittent issue. Begin by inspecting coil #1 wires and apply the wiggle test.
Inspect for loose connections and broken connector locks
If all the above don’t work change coil #1

P0354

Code Description:

Ignition Coil D Primary/Secondary Circuit Malfunction

Interpretation:

There’s a short in the driver circuit for the engine’s coil #4 (the coil for cylinder #4)

Key Signs:

Check Engine Light comes on
Engine misfire

Potential Causes:

Short or open in the coil on plug (COP) driver circuit
Loose or broken connection at the coil
Bad COP
Failed PCM

Diagnostic Procedure:

If the engine is not currently misfiring then it’s an intermittent problem. Start by checking coil #4 wires visually as well as using wiggle test
Check for loose connections and broken connector locks
If all the above don’t work replace the coil #4

P0400

Code Description:

Exhaust Gas Recirculation Flow Malfunction

Interpretation:

There is an insufficient or a non-existent amount of exhaust gases going into the cylinders

Key Signs:

Heightened NOx emissions
Increased combustion temperatures

Potential Causes:

Exhaust gas recirculation (EGR) passage is plugged
Bad EGR solenoid
Defective Wiring or harness to EGR solenoid
EGR valve is bad
Vacuum lines are damaged or disconnected from EGR valve or EGR valve solenoid

Diagnostic Procedure:

Using a bidirectional scanner, open and close EGR valve while the engine is operating. If the engine stumbles then there’s a wiring issue.
And if the engine doesn’t stumble but it dies then the ports are plugged
Afterward, examine all hoses, vacuum lines, solenoid, and solenoid harnesses for damage.
With the help of a diagnostic code reader, inspect solenoid voltage to confirm it’s within the normal range.
If all the above don’t work change the EGR valve

P0401

Code Description:

Exhaust Gas Recirculation Flow Insufficient Detected

Interpretation:

The PCM has determined an insufficient amount of EGR

Key Signs:

Engine pinging when the car is at high speed or under load

Potential Causes:

Faulty differential pressure feedback EGR (DPFE) sensor
Damaged EGR valve
EGR valve can’t open because of lack of vacuum
There is a blockage in EGR tube

Diagnostic Procedure:

Examine EGR valve and its tubing for deposits
Inspect DPFE sensor voltage to confirm it’s within the recommended range
If not change the sensor. If it is not functioning, change the EGR valve

P0402

Code Description:

Exhaust Gas Recirculation Flow Excessive Detected

Interpretation:

The PCM has discovered an excessive amount of EGR

Key Signs:

Engine surging off idle

Potential Causes:

Faulty differential pressure feedback EGR (DPFE) sensor
Bad EGR valve
EGR valve can’t open because of lack of vacuum
There is a blockage in EGR tube

Diagnostic Procedure:

Check DPFE sensor voltage to ensure it’s within the required range
If not change the sensor.

P0403

Code Description:

Exhaust Gas Recirculation Circuit Malfunction

Interpretation:

The PCM has determined that the EGR circuit has malfunctioned and isn’t sending the ideal voltage at the right time.

Key Signs:

Check Engine Light comes on
The engine may misfire when accelerated
It is rough idle

Potential Causes:

Short or open in the circuit leading to EGR solenoid
Pins connecting EGR solenoid are damaged or loose
Existence of water in EGR solenoid harness
EGR solenoid isn’t receiving voltage supply

Diagnostic Procedure:

Pull codes and freeze frame data to ascertain the P0403 code
Inspect all the wiring and connections to EGR solenoid
Disconnect and examine the EGR valve circuit for a short or open
Clear OBD code and do the test drive. If it comes back change solenoid

P0404

Code Description:

Exhaust Gas Recirculation Circuit Range/Performance

Interpretation:

The PCM has detected that EGR valve is open when it should be closed or it’s closed when it should be open.

Key Signs:

Check Engine Light comes on
The engine may idle rough
The engine may fail to idle
Car may fail emissions

Potential Causes:

Open or short in reference, ground or PCM controlled circuit
Bad PCM

Diagnostic Procedure:

Check all the wiring to EGR to confirm there are no shorts or opens
With the help of a bidirectional scan tool, open and close EGR valve as you watch the EGR position. If it’s not close to the “desired” position then there is a chance it’s a bad valve

P0405

Code Description:

Exhaust Gas Recirculation Sensor A Circuit Low

Interpretation:

The EGR valve pintle is not moving as it is needed either because of remarkably low voltage or its position is lower than the PCM has instructed.

Key Signs:

Check Engine Light turns on

Potential Causes:

Open or short in reference or ground circuit
Faulty EGR valve
Failed PCM

Diagnostic Procedure:

Check all the wiring to EGR to confirm there are no shorts or opens
Utilize a bidirectional diagnostic scan tool to open and close EGR valve and watch how it responds. If it’s moving well then it’s an irregular issue.

P0406

Code Description:

Exhaust Gas Recirculation Sensor A Circuit High

Interpretation:

The EGR sensor has had abnormally high voltage reading for too long

Key Signs:

Check Engine Light comes on
May surge when you drive
May stall intermittently
Vehicle may fail emissions

Potential Causes:

Defective EGR valve
Short or open in EGR wiring circuit
Debris build up in EGR valve and is holding it open

Diagnostic Procedure:

Pull codes and freeze frame data
Visually inspect all wiring to EGR to ensure there are no shorts or opens
Using a scan tool, view EGR position during startup and while running to ensure its correct
Clear code and do the test drive

P0411

Code Description:

Secondary Air Injection System Incorrect Flow Detected

Interpretation:

The flow coming from the secondary air injection system is out of the range suggested by PCM

Key Signs:

Check Engine Light comes on
The engine may hesitate when you accelerate

Possible Causes:

Faulty air injection pump
Inspect valve is bad or missing
Worn out or leak in exhaust component

Diagnostic Procedure:

Check air injection system and examine for broken parts, damaged hoses, and excess carbon
Reset the code and do a test drive

P0420

Code Description:

Catalyst System Efficiency Below Threshold (Bank 1)

Interpretation:

A catalytic converter is not functioning as efficiently as it should and the car is thus emitting more harmful particles.

Key Signs:

Check Engine Light comes on
The engine doesn’t have power
Lower fuel economy

Potential Causes:

Faulty O2 sensor
Bad engine coolant temp
Wiring to downstream O2 sensor is worn out or poorly done
A leak in the fuel injector
Contaminated oil
Applying leaded fuel where unleaded fuel was needed
The faulty catalytic converter, exhaust pipe, muffler or exhaust manifold

Diagnostic Procedure:

Examine the exhaust system for damage and leaks.
Inspect the voltage of the downstream O2 sensor while the engine is operating. If it’s not steady (jumpy between 0.1 and 0.9 V) then the catalytic converter should be changed

P0421

Code Description:

Warm-Up Catalyst Efficiency Below Threshold (Bank 1)

Interpretation:

The downstream O2 sensor on bank 1 has detected that the converter is not working according to specification.

Key Signs:

Check Engine Light comes on
The engine doesn’t have power
The engine may hesitate during acceleration

Potential Causes:

Bad catalytic converter
Faulty O2 sensor, particularly downstream O2 sensor
Fouled up the spark plug

Diagnostic Procedure:

Examine the voltage of the O2 sensor (both) and confirm they match the specs. If not then change as necessary.
Check catalytic converters and inspect for red fumes
Smell fumes and try to find traces of excessive fuel
If the latter two are present replace catalytic converter

P0430

Code Description:

Catalyst System Efficiency Below Threshold (Bank 2)

Interpretation:

The catalytic converter is not working as well as it should. It’s thus releasing more dangerous pollutants

Key Signs:

Check Engine Light comes on
The engine may lack power
Poor fuel economy

Potential Causes:

Bad O2 sensor
There is a leak in the exhaust system
Faulty catalytic converter

Diagnostic Procedure:

Inspect exhaust system for any leaks and damages
When the vehicle is running, Examine the voltage of downstream O2 sensor. If it’s not firm then the catalytic converter is worn out.

P0440

Code Description:

Evaporative Emission Control System Malfunction

Interpretation:

A part of the EVAP system is not working well

Key Signs:

Check Engine Light may come on

Potential Causes:

The gas cap is not functioning or has not been installed as needed
The canister is plugged and bad
Purge solenoid is not working

Diagnostic Procedure:

Check gas cap to see if it’s installed firmly
Faulty for disconnected or cracked EVAP hoses
Examine charcoal canister and fuel tank for leaks and damages
Inspect that purge valve (solenoid) doesn’t feature leaks

P0441

Code Description:

Evaporative Emission Control System Incorrect Purge Flow

Interpretation:

The PCM has determined that there’s no purge flow (i.e. purge control valve is still closed) regardless of commanding a purge.

Key Signs:

Check Engine Light may come on
There is a rough or erratic idle

Potential Causes:

Bad or loose EVAP hoses
Faulty purge valve
The gas cap is loose, missing or damaged
Faulty or damaged Charcoal canister

Diagnostic Procedure:

Check gas cap to see if its set up firmly
Examine for disconnected or cracked EVAP hoses
Check charcoal canister and fuel tank for leaks and damages
Inspect that purge valve (solenoid) has no leaks

P0442

Code Description:

Evaporative Emission Control System leak Detected (small leak)

Interpretation:

The PCM has discovered a very small vapor leak in the EVAP control system

Key Signs:

Check Engine Light may come on
Poor fuel economy

Potential Causes:

Damaged or loose EVAP hoses
Bad purge valve
The gas cap is loose, missing or damaged
The charcoal canister is leaking
A leakage in the fuel tank

Diagnostic Procedure:

View gas cap to know if it’s mounted tightly
Inspect for disconnected or cracked EVAP hoses
Check charcoal canister and fuel tank for leaks and damages
Examine that purge valve (solenoid) has no leaks
If the above doesn’t solve the issue, then conduct a smoke test

P0443

Code Description:

Evaporative Emission Control System Purge Control Valve Circuit Malfunction

Interpretation:

It is possible there’s an open in the purge control valve circuit or the circuit has an abnormal voltage (too high or too low)

Key Signs:

Check Engine Light may come on
The vehicle may have a lean condition

Potential Causes:

Driver circuit in PCM has an open or short
Short or open somewhere in the wiring harness to purge valve
Purge solenoid has short or open
Water intrusion has to lead the connector to break or wear out

Diagnostic Procedure:

With a scanner, instruct the purge valve to open. Listen for a clicking sound.
If it doesn’t click check solenoid and connectors for breakages and symptoms of excess wearing out.
Examine all the circuits for wiring problems

P0446

Code Description:

Evaporative Emission Control System Vent Control Circuit Malfunction

Interpretation:

The PCM has determined an open or short in EVAP control circuit or a short to ground circuit

Key Signs:

Check Engine Light comes on

Potential Causes:

Bad EVAP vent valve
There is a blockage in vent valve
Vent valve control circuit has an open or short

Diagnostic Procedure:

Inspect all the wiring to vent valve
If the above doesn’t, then change vent valve

P0449

Code Description:

Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction

Interpretation:

The PCM has discovered an issue in the circuit that controls the EVAP system vent

Key Signs:

Check Engine Light comes on

Potential Causes:

Circuit issue in the EVAP vent valve
Bad EVAP vent valve
Wiring issue in the EVAP vent valve

Diagnostic Procedure:

Inspect every wire leading to the vent valve for shorts and opens
View fuses that power the vent solenoid
Check if vent valve has cracks or openings
Apply a bidirectional automotive scanner to actuate the valve to check if its functioning

P0452

Code Description:

Evaporative Emission System Pressure Sensor/Switch Low

Interpretation:

The PCM has determined that the fuel tank pressure is extremely low

Key Signs:

Check Engine Light comes on

Potential Causes:

Faulty fuel tank pressure (FTP) sensor
Loose gas cap leading to loss of vacuum
Wiring issues in the circuits that lead to FTP sensor
Cracked or damaged vapor line (either to the tank or vacuum canister)
Leaking gasket in the fuel pump module

Diagnostic Procedure:

Examine vapor hoses for any breakages and opens
Diagnosing this issue is very challenging (because of the location of the FTP sensor), its suggested that you get a professional to help you out.

P0455

Code Description:

Evaporative Emission Control System Leak Detected (large leak)

Interpretation:

The PCM has determined a large vapor leak somewhere in the EVAP control system

Key Signs:

Check Engine Light may turn on
Lower fuel economy

Potential Causes:

Bad or loose EVAP hoses
The gas cap is loose, missing or worn out
Non-compatible gas cap

Diagnostic Procedure:

Examine gas cap to see if it’s mounted firmly
Inspect for disconnected or damaged EVAP hoses
Check charcoal canister and fuel tank for leaks and cracks
If the above don’t succeed, change the gas cap

P0456

Code Description:

Evaporative Emissions System – Small leak detected

Interpretation:

The FTP sensor has shown a small leak in the EVAP system

Key Signs:

Check Engine Light comes on

Potential Causes:

A leakage in fuel tank hoses or EVAP hoses
Bad gas cap
A leakage in the vent valve or purge valve
A leakage in EVAP canister

Diagnostic Procedure:

With a bidirectional diagnostic scanner, activate vent solenoid as you monitor FTP sensor. It will indicate if the system is sealing well or not
If it is, then you can apply a smoke test to see the leak

P0457

Code Description:

Evaporative Emission Control System (EVAP) Leak Detected

Interpretation:

A vacuum leak is present and the EVAP system can’t draw fuel vapors into the system for efficient burning.

Key Signs:

Check Engine Light comes on
Poor fuel economy
The smell of fuel in the exhaust

Potential Causes:

The gas cap is either loose, damaged or missing
Loose, disconnected or damaged hose in the EVAP system
Damaged vacuum canister

Diagnostic Procedure:

Check the gas cap and see if it’s loose or has debris that’s preventing it from mounting well
Examine vacuum hoses for damages and breaks
View charcoal canister for leaks

P0463

Code Description:

Evaporative Emission Control System Pressure Sensor High Input

Interpretation:

The signal from the fuel level sensor is above 5 volts for over a period.

Key Signs:

Check Engine Light comes on
Fuel light may come on and sound alarmed
Varying fuel level gauge
Fuel level gauge may incorrectly read empty or full

Potential Causes:

Faulty fuel level sensor
The issue with fuel level sensor circuit
Bad instrument cluster
Defective fuel tank

Diagnostic Procedure:

Check the fuel tank for cracks or leaks
View wiring harness
Do the voltage test on fuel level sensor circuit
If all those refuse to work out you may have to replace the fuel tank

P0500

Code Description:

Vehicle Speed Sensor Malfunction

Interpretation:

The car speed, as provided by the vehicle speed sensor (VSS) is not within the recommended range

Key Signs:

Check Engine Light comes on
ABS light may come on
Speedometer may refuse to work
Loss of ABS (anti-lock brakes)
Transmission may not function as needed

Potential Causes:

Damaged VSS
Wiring challenge in VSS circuit
PCM is not configured correctly for the tire size of the car

Diagnostic Procedure:

View all the wiring to VSS and inspect for open, short, broken and chaffed wires
Examine the voltage of the speed sensor

P0506

Code Description:

Idle Control System RPM Lower Than Expected

Interpretation:

The PCM has discovered that the engine idle speed is lower than the required RPM

Key Signs:

Check Engine Light comes on
There is rough idle due to lower idle speed

Potential Causes:

Vacuum leak
Air is restricted in the exhaust or intake air path
The bad positive crankcase ventilation valve
An issue with throttle body
Worn out PCM

Diagnostic Procedure:

Inspect vacuum leaks, cracks and restriction
It is important to know that this code is informational more than anything, so look out for other codes that it comes with and address them first.

P0507

Code Description:

Idle Control System RPM Higher Than Expected

Interpretation:

The PCM has determined that the engine idle speed is higher than the recommended RPM (normally over 200 RPM)

Key Signs:

Check Engine Light comes on

Potential Causes:

The faulty positive crankcase ventilation valve
Leaking air intake
Problem with throttle body
Vacuum leak
Bad EVAP system
Faulty idle air controller (IAC) or an issue with IAC circuit
Damaged PCM

Diagnostic Procedure:

Inspect for vacuum leaks, damages, and restriction
It is vital to understand that this code is informational more than anything, so check other codes that it comes with and handle those first.

P0521

Code Description:

Engine Oil Pressure Sensor/Switch Range/Performance

Interpretation:

The PCM has seen an unforeseen value in an engine oil pressure sensor. The value could be fixed when it should fluctuate or simply out of the usual range

Key Signs:

The oil pressure gauge may read too low or too high
Check Engine Light comes on
Oil pressure light may come on

Potential Causes:

Oil level in the engine is too low
Defective wiring to oil pressure sensor
Oil pressure is too low
Dirty oil

Diagnostic Procedure:

Examine that oil level is not extremely low
Inspect that the ideal oil was used
Check every wiring to the oil pressure sensor and check for open, short or broken wires
If possible, take the oil pressure reading and compare it with the reading indicated by the car’s PCM. That should show if the issue is with oil pressure

P0522

Code Description:

Engine Oil Pressure Sensor/Switch Low Voltage

Meaning:

The PCM has discovered an extremely low value in engine oil pressure sensor

Key Signs:

Check Engine Light comes on
The engine may stall during driving
The Oil pressure gauge reads zero or low value
The Oil pressure light comes on
The engine may fail to start

Potential Causes:

A problem with the wiring in the oil pressure sensor circuit
Faulty oil pressure sensor
Low oil level or blockage in the oil passage
Utilizing the wrong type of oil

Diagnostic Procedure:

View oil level and condition
Inspect every wiring to the oil pressure sensor
Examine the sensor’s voltage to confirm it meets the manufacturer’s specs
If possible, take the oil pressure reading and compare it with the reading indicated by the car’s PCM. That should show you if the problem is with oil pressure

P0562

Code Description:

System Voltage Low

Interpretation:

The PCM has found out that the ignition feed circuit has very low voltage. This implies that the charging system might not be working as it is supposed to.

Key Signs:

Check Engine Light comes on
Red battery light on
Poor fuel economy
Transmission may fail
The engine may fail to start
The engine may start then stall and die

Potential Causes:

Faulty alternator
High resistance either in the alternator-battery circuit, alternator-PCM circuit or both
Failed PCM

Diagnostic Procedure:

Inspect whether the battery voltage is right
Confirm the battery is well connected then view alternator belt
Use a digital volt-ohm meter (DVOM), inspect whether the charging system is functioning
Reset the code then do a test drive. If the code returns check PCM voltage

P0606

Code Description:

ECM/PCM Processor Fault

Interpretation:

The PCM has found out an integrity error in its own system

Main Symptoms:

Check Engine Light comes on

Potential Causes:

Defective PCM

Diagnostic Procedure:

Re-flash PCM with updated software. If that doesn’t function change the PCM

P0700

Code Description:

Transmission Control System Malfunction

Interpretation:

If the transmission control module (TCM) identifies an error in the transmission system and sets a code, this code is as well as kept in the PCM

Key Signs:

Check Engine Light comes on
Transmission may exhibit challenges

Potential Causes:

All transmission-linked challenges can trigger this code

Diagnostic Procedure:

This is simply an informational code, so pull all transmission codes, rectify them and do a test drive to fix this code.

P0705

Code Description:

Transmission Range Sensor Circuit Malfunction (PRNDL Input)

Interpretation:

The PCM has determined a malfunction in the transmission range sensor (TRS)

Key Signs:

Check Engine Light comes on
Actuating starter may be very difficult
Back up lights may not work
The engine may only start at neutral
Intermittent shift RPMs
Delayed transmission engagement
Lower fuel economy

Potential Causes:

Faulty TRS
Shorted wire in TRS circuit
Loose TRS
The loose or corroded connector at the external TRS. Pins may also be bent

Diagnostic Procedure:

It normally needs replacing the TRS

P0715

Code Description:

Input/Turbine Speed Sensor Circuit Malfunction

Interpretation:

The actual transmission input speed does not match the recommended input speed

Key Signs:

Check Engine Light comes on
Transmission may fail to shift
Transmission shifts unpredictably
Failure in speedometer
Reduced fuel economy

Potential Causes:

Bad input speed sensor
Faulty output speed sensor
A wiring issue in input/output speed sensor circuit
The loose or burnt connector in the transmission circuit
Poorly programmed PCM

Diagnostic Procedure:

Check all the wiring and connectors for loose, burnt, open or broken connections
Using a scan tool, pull all codes and freeze frame data to know which sensor is malfunctioning
Change sensor if need be

P0720

Code Description:

Output Speed Sensor Circuit Malfunction

Interpretation:

The PCM has detected that there’s a malfunction in the Output Shaft Speed Sensor (OSS) of the transmission system.

Key Signs:

Check Engine Light comes on
Delayed shifts
Worn out speedometer

Potential Causes:

Bad OSS
Faulty transmission fluid temperature sensor
Wiring issue in the OSS circuit

Diagnostic Procedure:

Examine that all wiring to OSS is rightly carried out and there are no open, broken or shorted wires
Inspect OSS voltage and match with manufacturer’s specs. If they don’t match change OSS
Check transmission fluid temperature sensor voltage and match with manufacturer’s specs. If they don’t match change the sensor

P0741

Code Description:

Torque Converter Clutch Circuit Performance or Stuck Off

Interpretation:

The TCM has found out a problem within the circuit that controls the torque converter clutch (TCC) solenoid

Key Signs:

Check Engine Light comes on
Lower fuel economy

Potential Causes:

Shorted wire in transmission’s ground circuit
Internal short in TCC solenoid
Bad TCM

Diagnostic Procedure:

Examine that all wiring in the transmission circuit is well done and there are no open, broken or shorted wires
Inspect the resistance of the TCC solenoid and match with manufacturer’s specs
Check TCM using an advanced scanner and view if its performance parameters are within the required range

P1101

Code Description:

MAF Sensor Out Of Self-Test Range./KOER Not Able To Complete KOER Aborted

Interpretation:

The PCM has determined an irregular (or abnormal) voltage from the Mass Air Flow (MAF) sensor

Key Signs:

Check Engine Light comes on
The engine performs unpredictably upon startup
Poor vehicle power
Rough idling

Potential Causes:

Bad MAF sensor
Wiring problem in MAF sensor circuit
Defective connector(s) in MAF system

Diagnostic Procedure:

Examine that all wiring in the MAF sensor circuit is well done and there are no open, broken or shorted wires
Inspect air filters for dirt and dirt that might be blocking air flow
Carry out the smoke test in a vacuum system to check for leaks before and after MAF sensor
View the voltage in the MAF sensor and match it with the manufacturer’s specs. If they don’t match change the sensor
Examine continuity between PCM and MAF sensor

P1133

Code Description:

HO2S Insufficient Switching Sensor 1

Interpretation:

The PCM has detected that the front heated O2 sensor (HO2S) is not working well

Key Signs:

Check Engine Light comes on
Difficult starting
Poor fuel economy
Rough or erratic idling

Potential Causes:

Faulty O2 sensor
Cracked, broken, shorted or corroded wires/connectors in front HO2S
EGR valve is stuck open
Misfires on at least one cylinder

Diagnostic Procedure:

Inspect that all O2 sensor wires and connectors are not cracked, open, broken, shorted or burnt
With a diagnostic scan tool, detect whether oxygen sensors are switching enough times
If not, check their voltage to comprehend which sensor is faulty. Replace it if need be

P1135

Code Description:

Air/Fuel Ratio Sensor Heater Circuit Malfunction Bank 1 Sensor 1

Interpretation:

This Toyota code means that the PCM has identified an oxygen sensor heater circuit malfunction

Key Signs:

Check Engine Light comes on
Longer time needed to achieve closed-loop
Decreased fuel economy
Engine may go into the fixed fuel mix

Potential Causes:

H02S sensor in bank 1, circuit 1 is not sending the correct signal to ECM
Damaged or failed element in heater circuit
Open in O2 sensor heater’s circuit
Open/short in O2 sensor heater’s battery
Defective ECM (this is the least likely cause)

Diagnostic Procedure:

Inspect wiring and power to the O2 sensor and ensure there’s no damage/open/short
Use code reader to pull engine codes
Examine voltage of O2 sensor and ensure it matches the manufacturer’s specs
Change O2 sensor if necessary

P1399

Code Description:

Random Cylinder Misfire Detected

Interpretation:

This Honda code means that the PCM has found out that there’s an engine cylinder that’s not firing the right way. It could be one or more cylinders as the PCM doesn’t specify the exact cylinder

Key Signs:

Check Engine Light comes on
Engine lacks power
Check Engine Light may flash
The engine may be difficult to start
The engine may stumble and hesitate often

Potential Causes:

Bad or worn out spark plugs
Low fuel pressure
Vacuum leak
Faulty catalytic converter
Bad fuel injector
Defective coil
The faulty camshaft position sensor
Bad crankshaft sensor
Problem with the distributor

Diagnostic Procedure:

With a diagnostic scan tool, pull codes and check if there are any other besides P0300. Rectify the others first
Examine whether there are loose, open or short wires in ignition coils
Check whether spark plugs and their wires are in a nice state
Inspect that fuel pressure is within the required range
Examine fuel injectors to know whether they are in perfect condition

P1450

Code Description:

Unable To Bleed Up Fuel Tank Vacuum

Interpretation:

This code can be found on a Ford, Jaguar, Lincoln, Mercedes, Mercury, and Oldsmobile and it means that the Evaporative Emission Control System has failed to bleed up the fuel tank

Key Signs:

Check Engine Light comes on
The engine may refuse to start

Potential Causes:

Bad vent valve
Obstruction in vacuum lines
Faulty charcoal canister
Overfilling fuel tank

Diagnostic Procedure:

Inspect that all vent valve wires and connectors are not cracked, open, broken, shorted or burnt
Get rid of any blockage in vacuum lines. Check your application manual for this method
Examine charcoal canister for any cracks
Inspect that the fuel amount is within the suggested range

P1457

Code Description:

This is a manufacturer-specific code that has different meanings for different vehicles

Acura – it means Evaporative emission (EVAP) canister purge system (canister system) – leak determined
Audi – it implies Exhaust gas recirculation temperature (EGRT) sensor 2/Bank 2 – open circuit/short to positive
Honda – it means Evaporative emission (EVAP) canister purge system (canister system) – leak discovered
Isuzu – it implies Evaporative emission (EVAP) canister purge system (canister system) – leak detected
Kia – it means Evaporative emission (EVAP) canister purge valve (low)
Volkswagen – it implies Exhaust gas recirculation temperature (EGRT) open circuit/short to positive

P1491

Code Description:

This is a manufacturer-specific code that has different meanings for different vehicles

Acura – it means Exhaust gas recirculation (EGR) system – valve lift insufficient
Chrysler – it implies Radiator Fan Relay Circuit Conditions
Honda – it means Exhaust gas recirculation (EGR) system – valve lift insufficient
Infiniti – it implies Evaporative emission (EVAP) canister purge control system – malfunction
Isuzu – it means Exhaust gas recirculation (EGR) system – valve lift insufficient
Mercedes – it implies AC system – pressure too high
Nissan – it means Evaporative emission (EVAP) canister purge system – bypass vacuum valve malfunction

P1494

Code Description:

EVAP Leak Detection Pump Pressure Switch Condition

Interpretation:

It is a Chrysler code, this code means the same as P0442, i.e. PCM has determined a very small vapor leak somewhere in the EVAP control system

Key Signs:

Check Engine Light may come on
Lower fuel economy

Potential Causes:

Damaged or loose EVAP hoses
Bad purge valve
The gas cap is loose, missing or damaged
Charcoal canister is leaking
The fuel tank is leaking

Diagnostic Procedure:

Examine gas cap to view if it’s installed firmly
Inspect for disconnected or damaged EVAP hoses
Check charcoal canister and fuel tank for leaks and cracks
Examine that purge valve (solenoid) has no leaks
If the above doesn’t work then you should perform a smoke test

P1516

Code Description:

Throttle actuator control module/throttle actuator position performance

Interpretation:

It is a GM code and it implies that the voltage being sent by the throttle actuator position sensor (TAPS) doesn’t match the voltage being received by the actual throttle position sensor

Key Signs:

Check Engine Light comes on
Car may fail to accelerate
Irregular surging
Poor fuel economy

Potential Causes:

Bad pedal position sensor
Open or short in circuit supplying power to pedal position sensor
Failed PCM

Diagnostic Procedure:

Check all the wiring to pedal position sensor and confirm there are no open, broken or shorted wires
Run a resistance test on sensor. If it fails then change it
Conduct a test drive, if the code returns carry out a test on PCM

P1684

Code Description:

Battery Power to Module Disconnected

Interpretation:

This code is linked with Dodge and Chrysler vehicles. It means the transmission control module (TCM) is disconnected from the battery’s power B+ or ground

Key Signs:

Check Engine Light comes on

Potential Causes:

Short in TCM harness
TCM was either replaced or disconnected
Recently disconnected battery
Bad TCM

Diagnostic Procedure:

Examine all the wiring to TCM and make sure there are no shorted, broken or open wires
With a scan tool, reset the code
Perform a voltage test on TCM to find out if it’s faulty

P2096

Code Description:

Post Catalyst Fuel Trim System Too Lean Bank 1

Interpretation:

There’s a lean condition (i.e. too much air and too little fuel) in cylinder #1 on a V6 or V8 engine.

Key Signs:

Check Engine Light comes on
Lower fuel economy
Unpredictable acceleration
Engine misfires
It is rough idle
May produce spark knock

Potential Causes:

Low fuel pressure
Large vacuum leak
Large air leak somewhere around the 1st cylinder
Misfiring plugs that cause the engine to run rough
Bad O2 sensor
Damaged exhaust system

Diagnostic Procedure:

With a diagnostic scanner, pull all the codes and handle all the others first
Check the exhaust system for any spoiled or worn-out components
Examine vacuum leaks in the engine, more so between the intake manifold and MAF sensor
Inspect that plug wires are not burning
If the car has very little acceleration power, inspect for clogged converter
If none of the above are able to resolve to replace the MAF sensor then downstream O2 sensor (in that order)

P2097

Code Description:

Post Catalyst Fuel Trim System Too Rich Bank 1

Interpretation:

There’s a rich condition (i.e. too little oxygen content) in cylinder #1

Key Signs:

Check Engine Light comes on
Engine lacks power
Lower fuel economy

Potential Causes:

Bad catalytic converter
Defective O2 sensor(s)
Faulty MAF sensor or manifold air pressure sensor
The leak in the exhaust system
Wiring challenge e.g. burnt, open, broken or disconnected wire

Diagnostic Procedure:

Check wiring harnesses for broken, open, burnt or disconnected wires
Inspect the exhaust for leaks and damages
Pull all codes and freeze frame data. Reset the codes and carry out a test drive
If code P2097 returns view resistance of MAF sensor and O2 sensors. Replace is need be

P2101

Code Description:

Throttle Actuator “A” Control Motor Circuit Range/Performance

Interpretation:

The code shows up when there’s an electrical or mechanical problem in the throttle actuator A (TA-A)

Key Signs:

Check Engine Light comes on
The engine refuses to accelerate
Fixed idle speed

Potential Causes:

Faulty TA-A
Open or short in TA-A circuit
Bad PCM

Diagnostic Procedure:

Identify TA-A and inspect all its wiring harnesses. Make sure there are no open, broken, disconnected, shorted or burnt wires and connectors
Readjust the code and perform a test drive. If it returns to test the actuator

P2138

Code Description:

Throttle/Pedal Pos Sensor/Switch D / E Voltage Correlation

Interpretation:

The PCM has found a fault in either the D or E (or both) circuit of the throttle position sensor

Key Signs:

Check Engine Light comes on
Car may refuse to start
Car may stall
Bad acceleration

Potential Causes:

The bad throttle position sensor
Faulty throttle body motor
Wiring or connector problem in throttle body motor circuit

Diagnostic Procedure:

Check the throttle body motor circuit for loose, broken, burnt or open wires and connectors
Test resistance of throttle motor and throttle position sensor. Change if needed

P2181

Code Description:

Cooling System Performance

Interpretation:

A vague OBD II code, the P2181 suggests that there’s somewhere in the engine where the temperature is out of range. It can be extremely hot or extremely cold.

Key Signs:

Check Engine Light comes on
Temperature gauge shows extremely high or extremely low temp
If the temp is extremely cold the engine will have a rich condition

Potential Causes:

Faulty engine coolant temperature (ECT) sensor
Wiring or connector problem in ECT circuit
Presence of air in the cooling system
The thermostat is stuck open or closed
Low engine coolant level

Diagnostic Procedure:

In case the engine is running very cold replace the thermostat
Inspect to confirm there are no open, broken, disconnected, shorted or burnt wires and connectors in ECT circuit
Examine whether the fan is functioning. If it’s wobbling or has a leak fasten or replace the fan. Don’t forget to inspect its fuse as well
Inspect the resistance of the ECT sensor. If it’s off the pre-determined reading replace the sensor

P2195

Code Description:

O2 Sensor Signal Stuck Lean Bank 1 Sensor 1

Interpretation:

The O2 sensor 1 on cylinder 1 (bank 1) is reading an air/fuel ratio that has strayed so far from the normal 14.7:1 that the PCM is no longer able to properly rectify the ratio

Key Signs:

Check Engine Light comes on

Potential Causes:

Bad O2 sensor or A/F (air/fuel) ratio sensor
Open or short in the O2 sensor circuit
Damaged fuel pressure system leading to very high or very low fuel pressure
Fuel leak
A leak in engine vacuum or intake air
Leak in PCV system
Failed PCM
Leak in fuel system (tank or hoses)
Faulty MAF sensor

Diagnostic Procedure:

View all the wiring harnesses to O2 sensor circuits, especially sensor 1
Examine vacuum, fuel tank and PCV systems for leaks
With a diagnostic scan tool, diagnose short and long term fuel trim values and compare with manufacturer specs.
Take readings for MAF and O2 sensor 1 and match with specs
Inspect the resistance of those sensors to confirm if they work well. Replace if needed

P2196

Code Description:

O2 Sensor Signal Stuck Rich Bank 1 Sensor 1

Interpretation:

This code is similar to P2195; i.e. O2 sensor 1 on cylinder 1 (bank 1) is reading an air/fuel ratio that has strayed so far from the normal 14.7:1 that the PCM can’t correct the ratio

Key Signs:

Check Engine Light comes on

Potential Causes:

Bad O2 sensor or A/F (air/fuel) ratio sensor
Open or short in the O2 sensor circuit
Faulty fuel pressure system causing very high or very low fuel pressure
Fuel leak
Leak in engine vacuum or intake air
Leak in PCV system
Damaged MAF sensor
Leak in fuel system (tank or hoses)
Bad PCM

Diagnostic Procedure:

Examine every wiring harnesses to O2 sensor circuits, more so sensor 1
Test vacuum, fuel tank and PCV systems for leaks
Utilize a scanner to diagnose short and long term fuel trim values and compare with manufacturer specs.
Take readings for MAF and O2 sensor 1 and match with specs
Inspect the resistance of those sensors to make sure they work as needed. Change if required

P2270

Code Description:

O2 Sensor Signal Biased/Stuck Lean Bank 1 Sensor 2

Interpretation:

The signal being displayed by sensor 2 on bank 1 is stuck lean (the sensor has detected too much air)

Key Signs:

Check Engine Light comes on
Engine may run rough

Potential Causes:

The issue with a fuel injector
Exhaust leak near sensor 2 of bank 1
Faulty sensor 2 of bank 1
Incorrect fuel pressure
The leak in engine coolant
Bad purge solenoid valve
Failed PCM

Diagnostic Procedure:

Inspect every wiring harnesses to O2 sensor circuits, especially sensor 1 of bank 1
Test for exhaust leaks
Using an automotive scanner, check sensor readings and match with manufacturer specs
Examine resistance of sensors and replace if need be

P2646

Code Description:

“A” Rocker Arm Actuator System Performance/Stuck Off Bank 1

Interpretation:

The “A” rocker arm actuator control circuit is either stuck in the off position or not working as it should

Key Signs:

Check Engine Light comes on
The engine may lack power
Engine valve train may be too noisy

Potential Causes:

Clogged oil passages
Low oil pressure
Oil utilized is too thick
Rocker arm actuator has a built-up slug

Diagnostic Procedure:

Ensure that the oil used is of the right viscosity
Inspect A” rocker arm actuator hoses and passages for obstruction
Remove code and perform a test drive. If it returns perform manufacturer pinpoint test for A” rocker arm actuator

P2A00

Code Description:

O2 Sensor Circuit Range/Performance Bank 1 Sensor 1

Interpretation:

The upstream O2 sensor circuit has failed to cycle as expected by the PCM over a period of time predetermined by the PCM

Key Signs:

Check Engine Light comes on
Lower fuel economy
Pathetic engine performance
Engine misfires

Potential Causes:

Bad O2 sensor 1 in bank 1
Burnt, open, broken, shorted or disconnected wire/connector in the sensor circuit
There is a vacuum leak
Faulty MAF sensor
The leak in engine exhaust

Diagnostic Procedure:

Check all the wiring harnesses to O2 sensor circuits, especially sensor 1 of bank 1
Test for leaks in engine and vacuum system
Handle other codes, reset all codes and perform a test drive. If the code returns test resistance of MAF sensor and O2 sensor. Change if required.

Popular Chassis (C) OBD II Codes

C0265

Code Description:

EBCM Motor Relay Circuit Low When On

Interpretation:

The Electronic Brake Control Module (EBCM) is sending an unpredictably low voltage signal

Key Signs:

ABS warning light comes on
Check Engine Light may come on

Potential Causes:

Shorted or open wire in EBCM harness
The bad electrical connection in EBCM circuit
Faulty EBCM

Diagnostic Procedure:

Examine all the wiring and connectors in EBCM for loose, open or shorted connections
Check EBCM for resistance and compare readings with manufacturer’s specs. If they are out of range consider changing them

C1130

Code Description:

Engine Signal 1

Interpretation:

The ABS control module has discovered that there’s an issue with the engine control unit (ECU) or PCM

Key Signs:

ABS warning light comes on
Check Engine Light comes on

Potential Causes:

Faulty ECU
Bad ABS actuator and/or ABS control module
Problem with CAN communication line
Defective controller(s) because of unnatural system voltages

Diagnostic Procedure:

Detect and rectify all other codes first before changing ECU
Inspect whether system voltage is within manufacturer’s suggestion
Examine wiring to ECU and confirm that there are no open, shorted or broken wires
Test all fuses and replace as if need be
Conduct tests on ABS module
Run tests on CAN line
Readjust all codes and perform a test drive. If the code returns you may have to change ECU

C1145

Code Description:

Right Front Wheel Speed Sensor Input Circuit Failure

Interpretation:

The right front wheel speed, as provided by the wheel’s speed sensor is not within the required range

Key Signs:

ABS warning light comes on
Check Engine Light comes on

Potential Causes:

Faulty right front wheel speed sensor
A wiring problem in that speed sensor’s circuit
PCM is not configured as needed for the size of the right front wheel

Diagnostic Procedure:

Inspect every wiring to the right front wheel speed sensor and check for open, short, broken and chaffed wires
Examine the voltage of the speed sensor and match it with manufacturer specs. If they don’t match change the sensor

C1201

Code Description:

Engine Control System Malfunction

Interpretation:

The Electronic Control Unit (ECU) has failed

Key Signs:

Check Engine Light comes on
Additional warning lights may emerge depending on which module is affected

Potential Causes:

Faulty ECU
Defective controller(s) because of abnormal system voltages

Diagnostic Procedure:

Verify and correct all other codes first before replacing ECU
Inspect whether system voltage is within manufacturer’s recommendation
Examine the wiring to ECU and ascertain that there are no open, shorted or broken wires
Readjust all codes and do the test drive. If the code returns you may have to replace ECU

C121C

Code Description:

Torque Request Signal Denied

Interpretation:

This camshaft-related code is informational. It comes with codes P0344, P0345, or P0365. Diagnosing those codes will remove this one

C1223

Code Description:

ABS Control System Malfunction

Interpretation:

This code comes about when the vehicle’s stability control (VSC) system identifies any malfunction in the ABS

Key Signs:

ABS warning light comes on
Check Engine Light comes on

Potential Causes:

Faulty ABS control module
Open or short in the ABS circuit
Bad ABS sensor

Diagnostic Procedure:

Test all wiring in the ABS circuit for loose, open or short connections
Carry out resistance tests on ABS sensors and modules. Replace as necessary
Reset code and conduct drive cycle, if it returns probe other systems, including PCM

C1233

Code Description:

Left Front Wheel Speed Sensor Input Signal Missing

Interpretation:

The PCM or car speed sensor (VSS) has failed to receive signals from the Left Front Wheel Speed Sensor

Key Signs:

ABS warning light comes on
Check Engine Light comes on

Potential Causes:

Bad connection in Left Front Wheel Speed Sensor
Open, shorted or broken wire in Left Front Wheel Speed Sensor harness
FaultyLeft Front Wheel Speed Sensor

Diagnostic Procedure:

Inspect every wiring in the Left Front Wheel Speed Sensor circuit for loose, open or short connections
Conduct resistance test on Left Front Wheel Speed Sensor.
Reset code and do drive cycle, if it returns probe ABS system entirely

C1234

Code Description:

Right Front Wheel Speed Sensor Input Signal Missing

Interpretation:

The PCM or car speed sensor (VSS) has failed to get signals from the Right Front Wheel Speed Sensor

Key Signs:

Check Engine Light comes on
ABS warning light comes on

Potential Causes:

Pathetic connection in Right Front Wheel Speed Sensor
Open, shorted or broken wire in Right Front Wheel Speed Sensor harness
Bad Right Front Wheel Speed Sensor

Diagnostic Procedure:

Examine every wiring in the Right Front Wheel Speed Sensor circuit for loose, open or short connections
Carry out resistance test on Right Front Wheel Speed Sensor.
Clear OBD2 code and conduct drive cycle, if it returns probe ABS system entirely

C1241

Code Description:

Low Battery Positive Voltage

Interpretation:

This code comes about when there’s a problem with the skid control ECU (master cylinder solenoid)

Key Signs:

Check Engine Light comes on
ABS warning light comes on

Potential Causes:

Low battery voltage
Running on an incorrect battery
Poorly maintained battery
High resistance either in the alternator-battery circuit, alternator-PCM circuit or both
Faulty charging system

Diagnostic Procedure:

Inspect whether or not the battery voltage is sufficient
Confirm battery is well connected then check the alternator belt
With a digital volt-ohm meter (DVOM), check whether the charging system is working
Readjust the code then carry out a test drive. If the code returns view PCM voltage

C1713

Code Description:

Right Rear Height Control Sensor

Interpretation:

The PCM has identified that after turning the ignition on, a voltage of .3V or less, or 4.7V or more was attained for more than 1 second at each height control sensor sub−assy rear.

Key Signs:

Check Engine Light comes on
Height control indicator lamp (N) comes on or blinks
The car will not perform a height control function

Potential Causes:

Bad Right Rear Height Control Sensor
Wiring issue in Right Rear Height Control Sensor
Damaged suspension and ride control parts
Issue with shocks and/or struts

Diagnostic Procedure:

Check all the wiring in the RIGHT Rear Height Control Sensor circuit for loose, open or short connections
Do a resistance test on Right Rear Height Control Sensor. Replace if necessary
Make sure that every section, including ball joints, springs (for ride height), shocks and struts are properly maintained,

Popular User Network & OBD II Codes

U0001

Code Description:

Controller Area Network (CAN) Data Bus: High-Speed Bus/Communication Control Module

Interpretation:

The high-speed bus is a communication line between the totally integrated power module (TIPM) and other car modules. If this code shows up, it means there’s a module (especially ABS module) that has failed to communicate with TIPM

Key Signs:

Check Engine Light comes on
Car may refuse to start on one or few attempts
The key alarm may activate intermittently

Potential Causes:

Open in either positive or negative CAN bus circuit
Short to ground on CAN bus circuit
Open in power or ground supply circuit to the module that set the code
Issue with TIPM
Low voltage

Diagnostic Procedure:

With a bidirectional scanner, operate each module independently to discover which one is not functioning
After you’ve detected the module examines that its circuits have no loose, open, broken or disconnected wires and connectors
Repeat the same procedure for TIPM
Apply an ohmmeter to verify continuity on wire terminals in the module and TIPM
If the steps don’t work, then replace the TIPM

U0073

Code Description:

Control Module Communication Bus “A” Off

Interpretation:

There is an issue with CAN bus making it difficult for modules to exchange information and to communicate with the scan tool

Key Signs:

Check Engine Light comes on
Instrument cluster indicator “light” on
Poor fuel economy
The engine doesn’t have power

Potential Causes:

Open in the “A” CAN bus + or – circuit
Short to power or ground in “A” CAN bus circuit

Diagnostic Procedure:

Pull all communication codes and rectify them first then this one last
Check all bus communication connections (connectors and wires) for breaks, shorts, opens, chafing, burns and melted spots
Readjust all codes and perform a test drive. If this code returns disconnect one control module at a time and check if the scan tool can communicate with PCM

U0101

Code Description:

Lost Communication With Transmission Control Module

Interpretation:

It means a lack of communication between the transmission control module (TCM) and other control modules.

Key Signs:

Check Engine Light comes on
The vehicle doesn’t shift gears
Remains in one gear, usually 2nd or 3rd gear

Potential Causes:

Open in CAN bus + or – circuit
Short to power or ground in either + or – CAN bus circuit
Bad TCM

Diagnostic Procedure:

With a bidirectional scanner like Foxwell Elite NT630, control TCM and watch if it responds. If it doesn’t probe it further
If it responds then inspect all the wires, connectors and fuses that make the circuit
With the key on engine off, check the voltage of CAN C+ and C-. If the readings don’t correspond manufacturer’s specs then the communication circuits are bad

U0107

Code Description:

Lost Communication With Throttle Actuator Control Module

Interpretation:

The code indicates a lack of communication between the throttle actuator control (TAC) module and other control modules

Key Signs:

Check Engine Light comes on
No throttle response
Electronic throttle control light comes on or flashes

Potential Causes:

Open in CAN bus + or – circuit
Short to power or ground in either + or – CAN bus circuit
Bad TAC module

Diagnostic Procedure:

With a bidirectional diagnostic scan tool, control TAC module and view it if it responds. If it doesn’t probe it further. You can use an Autel Maxisys Pro MS908P for better accuracy
If it responds then examine every wire, connector and fuse that make the circuit
Using a key on engine off, check the voltage of CAN C+ and C-. If the readings don’t correspond manufacturer’s specs then the communication circuits are bad

U0121

Code Description:

Lost Communication With Anti-Lock Brake System Control Module

Interpretation:

Lack of communication between the anti-lock brake system (ABS) control module and other control modules

Key Signs:

Check Engine Light comes on
ABS warning light comes on
TRAC or ESP/ESC (or both) warning light comes on

Potential Causes:

Open in CAN bus + or – circuit
Short to power or ground in either + or – CAN bus circuit
Faulty ABS control module

Diagnostic Procedure:

Using a bidirectional automotive scanner, control ABS control module and check if it responds. If it does not check it further. The Autel Maxidas DS808 automotive tool would be ideal for this test
If it responds then test all the wires, connectors and fuses that make the circuit
Using the key on engine off, inspect the voltage of CAN C+ and C-. If the readings don’t complement manufacturer’s specs then the communication circuits are faulty

U0155

Code Description:

Lost Communication with Instrument Panel Control Module

Interpretation:

It indicates a lack of communication between the instrument panel control (IPC) module and other control modules

Key Signs:

Check Engine Light comes on
All indicator lights in instrument panel/cluster come on, or
There are no indicator lights in instrument panel/cluster come on

Potential Causes:

Open in CAN bus + or – circuit
Short to power or ground in either + or – CAN bus circuit
Bad IPC module

Diagnostic Procedure:

With an Autel MaxiSys MS906BT Bluetooth bidirectional scanner, control IPC module and view it if it responds. If it does not examine it further
If it reacts then inspect all the wires, connectors and fuses that make the circuit
Using the key on engine off, check the voltage of CAN C+ and C-. If the readings don’t correspond manufacturer’s specs then the communication circuits are faulty

U1000

Code Description:

This Is A Manufacturer-Specific Code That Means Different Things In Different Cars

Infiniti – it means CAN Communication Line – Signal Malfunction
Isuzu – it implies Class 2 Communication ID Not Learned
Nissan It means CAN Communication Circuit
GM – it implies Class 2 Communication Malfunction Conditions

Diagnostic Procedure:

This code is usually informational and it comes with other network codes. Diagnosing all the codes that it comes with will fix/reset this code, too.

U1120

Code Description:

Lost Wheel Distance

Interpretation:

It is a Chrysler code. The U1120 implies that the ABS module is not able to communicate with speed sensors

Key Signs:

Check Engine Light comes on
ABS warning light may come on

Potential Causes:

Open in CAN bus + or – circuit
Bad ABS control module (least likely)
Short to power or ground in either + or – CAN bus circuit

Diagnostic Procedure:

With a bidirectional scanner such as Upgraded LAUNCH X431 V+, manage ABS control module and check if it responds. If it doesn’t, examine it further
If it responds, inspect all the wires, connectors and fuses that make the circuit
Using the key on engine off, examine the voltage of CAN C+ and C-. If the readings don’t complement manufacturer’s specs then the communication circuits are damaged

U1900

Code Description:

CAN Communication Bus Fault

Interpretation:

The Primarily a Ford code, the U1900 means the same as U0001

Key Signs:

Check Engine Light comes on
Car may refuse to start on one or few attempts
The key alarm may set off intermittently

Potential Causes:

Open in either positive or negative CAN bus circuit
Open in power or ground supply circuit to the module that set the code
Low voltage
Short to ground on CAN bus circuit
An issue with TIPM

Diagnostic Procedure:

With the help of a bidirectional diagnostic scan tool, examine each module separately to know which one is not working
After you’ve identified the module, observe that its circuits have no loose, open, broken or disconnected wires and connectors
Repeat for TIPM
With an ohmmeter, examine continuity on wire terminals in the module and TIPM
If all the steps refuse to work, replace the TIPM

Popular Body (B) Codes

B0092

Code Description:

Left Side Restraints Sensor 2

Interpretation:

It is a Ford code, the B0092 implies that the left side airbag sensor has identified an issue with the airbag system.

Key Signs:

Airbag warning lights may come on
Excessive illumination of airbag warning lights

Potential Causes:

Open, short or broken wire in left side restraint sensor 2 harness
Faulty left side restraint sensor 2

Diagnostic Procedure:

Examine every wiring to left side restraint sensor 2 for loose, open or short connections
Measure resistance of left side restraint sensor 2 and match with specs. If they don’t match, then you’ve to change the sensor

B1015

Code Description:

This is a manufacturer-specific code that means different things in different vehicles

Chrysler – it Means Rear Defrost Switch Request Input Circuit/Performance
GM – it Means Passenger Deploy. Loop Resistance High
Ford – it Means Electronic Instrument Cluster Unconfigured
Mazda – it Means Electronic Instrument Cluster Unconfigured
Mitsubishi – it Means Heater Water Temperature Sensor Performance

B1047

Code Description:

Driver-Side Side Air Bag Module And Other Air Bag Module Circuits Short

Interpretation:

It indicates that there’s a short in the side airbag on the driver’s side

Key Signs:

Airbag warning lights may come on
Excessive illumination of airbag warning lights

Potential Causes:

Open or short in the circuit leading to driver-side side air bag module
Faulty driver-side side air bag module
Bad SRS (airbag) module

Diagnostic Procedure:

Check all wiring to the driver-side side air bag module for loose, open or short connections
Conduct resistance test on driver-side side air bag module
Carry out resistance test on the airbag control module

B1057

Code Description:

Driver Airbag Module Short

Interpretation:

The airbag diagnosis sensor on the driver’s side has determined a short in the circuit

Key Signs:

The airbag warning light comes on

Potential Causes:

Short in driver airbag’s harness
Issue with spiral cable
Worn out driver airbag
Problem with electrical connection in driver airbag

Diagnostic Procedure:

Inspect the wiring harness to driver’s airbag
Measure resistance test on driver’s airbag module
Test resistance of spiral cable and airbag diagnosis sensor. Replace it if need be

B1318

Code Description:

Battery Voltage Low

Interpretation:

This code is for Ford and Jaguar and comes on when the PCM identifies that battery voltage has fallen below a recommended level

Key Signs:

Check Engine Light comes on
Red battery light on
Poor fuel economy
Transmission may fail
The engine may refuse to start
The engine may start then stall and die

Potential Causes:

Faulty alternator
Using an incorrect battery
Badly maintained battery
High resistance either in the alternator-battery circuit, alternator-PCM circuit or both
Bad PCM

Diagnostic Procedure:

Verify whether the battery voltage is sufficient
Make sure the battery is excellently connected then inspect alternator belt
With a digital volt-ohm meter (DVOM), test whether the charging system is working
Reset the code then execute a test drive. If the code returns, then inspect PCM voltage

B1342

Code Description:

ECU Is Defective

Interpretation:

The Electronic Control Unit (ECU) is not working

Key Signs:

Check Engine Light comes on
Other warning lights may show up depending on which module is affected

Potential Causes:

Bad ECU
Worn out controller(s) due to abnormal system voltages

Diagnostic Procedure:

Test and diagnose all other codes first before changing ECU
Inspect whether system voltage is within manufacturer’s guidelines
Examine every wiring to ECU and make sure that there are no open, shorted or broken wires
Reset all codes and execute a test drive. If the code returns you may be required to replace ECU

B1650

Code Description:

Occupant Classification System Fault

Interpretation:

The PCM or airbag control module has identified a malfunction in the occupant classification system

Key Signs:

The airbag warning light comes on
Check Engine Light may come on

Potential Causes:

Challenges in the occupant classification system
Problem with wiring in the right front seat
The issue with airbag sensor assembly center

Diagnostic Procedure:

Visually inspect all wiring in the occupant classification system for loose, open or short connections
Measure resistance test on the occupant classification system and airbag sensor assembly center
Carry out resistance tests on the airbag control module. If it doesn’t pass the test then change the module

B1676

Code Description:

Battery Pack Voltage Out Of Range

Interpretation:

This anti-lock brake system (ABS) code coms about when the ABS module determines a voltage signal that’s less than 9v or more than 19v for more than 8 seconds

Key Signs:

ABS warning light comes on
Check Engine Light may come on

Potential Causes:

Blown fuse in ABS
The issue in the charging system
Problem within ABS module connector
Faulty ABS module

Diagnostic Procedure:

Check every wiring and connectors in ABS module as well as a charging system for loose, open or short connections
Inspect that all fuses in ABS are not blown. If there is any blown fuse, change it.
Measure resistance of ABS module and match it with the manufacturer’s specs
Reset code and conduct test drive. If it returns to think of replacing the module

With all of these diagnostic trouble codes and their meaning, diagnosing your car has been made easy. Ensure to acquire a high-quality and reliable TPMS OBD2 code reader to give you accurate results every time you inspect why your check engine light is on. Examine all the major car systems with much ease by referring to this obd2 code list. We hope you’ve found all the OBD II codes that your vehicle has been displaying during diagnosing! Feel free to ask a question or leave a comment below.