Home » OBD2 Codes List and Meaning [signs, causes & diagnostic procedure]

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, OBD2 diagnostic users utilize 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 OBD2 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

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 allow you to interpret the code.

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

OBD2 Codes List

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

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

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

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

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

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

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

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

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

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.

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.

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

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

Page Contents

 Popular Powertrain (P) OBD2 Codes

P0008

  1. Code Description:

Engine Position System Performance – Bank 1

  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.

  1. Key Signs:
  • Check Engine Light comes on
  • Reduced power
  • Rough acceleration
  • Lower fuel economy
  1. 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
  1. Diagnostic Procedure:
  • Apply a sophisticated code reader to pull engine codes
  • Inspect the VCT/VVT circuit for open/damaged wires.

P0010

  1. Code Description:

Intake Camshaft Position Actuator Circuit / Open (Bank 1)

  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.

  1. Key Signs:
  • Check Engine Light comes on
  • Engine performs badly at high RPM
  • Vehicle runs roughly
  • Lower fuel economy
  • Vehicle doesn’t pass emission test
  1. 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
  1. 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

  1. Code Description:

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

  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

  1. 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
  1. 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
  1. 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

  1. Code Description:

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

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • Rough start
  • Poor fuel economy
  • Vehicle may run rough or stall
  • Vehicle may fail the emission test
  1. 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
  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

  1. Code Description:

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

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • Rough start
  • Bad fuel economy
  • Vehicle may run rough or stall
  • Vehicle may fail the emission test
  1. 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
  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

  1. Code Description:

Crankshaft Position Camshaft Position Correlation Bank 1 Sensor A

  1. 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.

  1. 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
  1. 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
  1. 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

  1. Code Description:

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

  1. 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.

  1. 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
  1. 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
  1. 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

  1. Code Description:

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

  1. Interpretation:

The camshaft timing for bank 2 is over-retarded

  1. Key Signs:
  • Check Engine Light comes on
  • Vehicle stalls
  • It hard starts
  1. 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
  1. 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

  1. Code Description:

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

  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.

  1. 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
  1. 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
  1. 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

  1. Code Description:

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

  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.

  1. Key Signs:
  • Check Engine Light comes on
  • This is rare, but ECM may enter failsafe mode
  1. 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
  1. 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

  1. Code Description:

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

  1. 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.

  1. 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
  1. 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
  1. 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

  1. Code Description:

Fuel Rail/System Pressure – Too Low

  1. 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

  1. Key Signs:
  • Check Engine Light comes on
  • Vehicle may have a rich fuel condition
  • The vehicle may also misfire
  • Vehicle may operate poorly
  1. 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
  1. 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

  1. Code Description:

Mass or Volume Air Flow Circuit Low Input

  1. 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)

  1. 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
  1. 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
  1. 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

  1. Code Description:

Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem

  1. 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.

  1. 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
  1. 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
  1. 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

  1. Code Description:

Manifold Absolute Pressure/Barometric Pressure Circuit Low Input

  1. 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.

  1. 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
  1. 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)
  1. 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

  1. Code Description:

Manifold Absolute Pressure/Barometric Pressure Circuit High Input

  1. 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.

  1. 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
  1. 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
  1. 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

  1. Code Description:

Intake Air Temperature Circuit High Input

  1. 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.

  1. Key Signs:
  • Check Engine Light comes on
  • The engine may run extra lean
  1. 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
  1. 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

  1. Code Description:

Engine Coolant Temperature Circuit Range/Performance Problem

  1. 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.

  1. 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)
  1. Potential Causes:
  • The thermostat is either missing or open
  • A bad ECT sensor
  • Open or short in ECT signal or ground circuit
  1. 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

  1. Code Description:

Engine Coolant Temperature Circuit High Input

  1. 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.

  1. 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)
  1. Potential Causes:
  • Defective ECT sensor
  • Open or short in ECT signal or ground circuit
  • PCM is defective
  1. 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

  1. Code Description:

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

  1. Interpretation:

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

  1. 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
  1. Potential Causes:
  • Faulty TPS
  • Open or short in TPS circuit
  • Bad connection to TPS
  • PCM is bad
  1. 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

  1. Code Description:

Throttle/Pedal Position Sensor/Switch A Circuit Low Input

  1. 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

  1. M:
  • Check Engine Light comes on
  • Extremely high idle
  • Rough or low idle
  • The vehicle stalls
  • Acceleration is poor or low
  1. Potential Causes:
  • Defective TPS
  • Open or short in TPS circuit
  • Wrong mounting of TPS after replacement
  • TPS has loosened
  • A defective PCM
  1. 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

  1. Code Description:

Throttle/Pedal Position Sensor/Switch A Circuit High Input

  1. 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.

  1. Key Signs:
  • Check Engine Light comes on
  • Extremely high idle
  • Rough or low idle
  • Frequent surges
  1. 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)
  1. 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

  1. Code Description:

Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)

  1. Interpretation:

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

  1. 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
  1. 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
  1. 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

  1. Code Description:

O2 Sensor Circuit Malfunction (Bank 1 Sensor 1)

  1. Interpretation:

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

  1. 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
  1. 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
  1. 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

  1. Code Description:

O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)

  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.

  1. 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
  1. 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
  1. 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

  1. Code Description:

O2 Sensor Circuit High Voltage (Bank 1 Sensor 1)

  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.

  1. 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.

  1. Potential Causes:
  • Fuel temp is very high
  • Short, open or broken wire in O2 sensor circuit
  1. 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

  1. Code Description:

O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)

  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

  1. 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.

  1. Potential Causes:
  • A faulty first O2 sensor in bank 1
  • Short, open or broken wire in the O2 sensor circuit
  • An exhaust leak
  1. 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

  1. Code Description:

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

  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.

  1. 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
  1. 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
  1. 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

  1. Code Description:

O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

  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.

  1. Key Signs:
  • Check Engine Light comes on
  • Lower fuel economy
  1. Potential Causes:
  • Short, open or broken wire in O2 heating system
  • Great resistance in O2 heater element or circuit
  1. 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

P0136

  1. Code Description:

O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)

  1. 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.

  1. Key Signs:
  • Check Engine Light comes on
  • The vehicle produces black smoke (visible at tailpipe)
  • Bad fuel economy
  • The engine may fail to start totally
  • In case it starts it may run rough and/or stumble
  1. 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
  1. 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

  1. Code Description:

O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)

  1. Interpretation:

The PCM has detected that the O2 sensor may be inactive

  1. Key Signs:

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

  1. 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
  1. 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

  1. Code Description:

O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)

  1. 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.

  1. Key Signs:

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

  1. Potential Causes:
  • Fuel temp is extremely high
  • Short, open or broken wire in the O2 sensor circuit
  1. 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

  1. Code Description:

O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)

  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.

  1. Key Signs:

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

  1. 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
  1. 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

  1. Code Description:

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

  1. 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.

  1. 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
  1. 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
  1. 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

  1. Code Description:

O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

  1. 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.

  1. Key Signs:
  • Check Engine Light comes on
  • Low fuel economy
  1. Potential Causes:
  • Short, open or broken wire in O2 heating system
  • High resistance in O2 heater element or circuit
  1. 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

  1. Code Description:

O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)

  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.

  1. 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
  1. 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
  1. 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

  1. Code Description:

O2 Sensor Circuit Slow Response (Bank 2 Sensor 1)

  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

  1. Key Signs:
  • Check Engine Light may come on and
  • Poor fuel economy
  1. Potential Causes:
  • First O2 sensor in bank 2 is faulty
  • Short, open or broken wire in the O2 sensor circuit
  • Exhaust leak
  1. 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

  1. Code Description:

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

  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

  1. Key Signs:
  • Check Engine Light comes on
  • The car emits black smoke
  • Bad fuel economy
  • The engine may run rough and/or stumble
  1. 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
  1. 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

  1. Code Description:

O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)

  1. 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

  1. 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
  1. 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
  1. 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

  1. Code Description:

O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)

  1. 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.

  1. Key Signs:
  • Check Engine Light turns on
  • Lower fuel economy
  1. Potential Causes:
  • Short, open or broken wire in O2 heating system
  • Great resistance in O2 heater element or circuit
  1. 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

  1. Code Description:

System Too Lean (Bank 1)

  1. Interpretation:
  • There’s a lean condition in bank 1; i.e. there’s excess oxygen in the exhaust
  1. Key Signs:
  • The decrease in engine power
  • The vehicle hesitates then surges when accelerated
  • It is rough idle
  1. 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
  1. 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

  1. Code Description:

System Too Rich (Bank 1)

  1. Interpretation:

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

  1. Key Signs:

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

  1. Potential Causes:
  • Dirty or defective MAF sensor
  • MAF sensor has a vacuum leak
  • The problem relating to fuel pressure or delivery
  1. 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

  1. Code Description:

System Too Lean (Bank 2)

  1. Interpretation:

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

  1. Key Signs:
  • Great decrease in engine power
  • Vehicle hesitates then increases when accelerated
  • Rough idle
  1. 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
  1. 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

  1. Code Description:

System Too Rich (Bank 2)

  1. Interpretation:

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

  1. Key Signs:

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

  1. Potential Causes:
  • Filthy or defective MAF sensor
  • The MAF sensor has a vacuum leak
  • An issue relating to fuel pressure or delivery
  1. 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

  1. Code Description:

Fuel Rail Pressure Sensor Circuit High Input

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • The engine cranks but doesn’t start
  • Vehicle hesitates upon the increase of speed
  1. Potential Causes:
  • Faulty fuel rail pressure (FRP) sensor
  • Bad fuel pump
  • Open or short in FRP circuit
  • Low or no fuel in the tank
  1. 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

  1. Code Description:

Random/Multiple Cylinder Misfire Detected

  1. 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.

  1. 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
  1. 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
  1. 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

  1. Code Description:

Cylinder 1 Misfire Detected

  1. Interpretation:

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

  1. 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
  1. 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
  1. 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

  1. Code Description:

Cylinder 2 Misfire Detected

  1. Interpretation:

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

  1. 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
  1. 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
  1. 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

  1. Code Description:

Cylinder 3 Misfire Detected

  1. Interpretation:

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

  1. 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
  1. 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
  1. 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

  1. Code Description:

Cylinder 4 Misfire Detected

  1. Interpretation:

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

  1. 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
  1. 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
  1. 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

  1. Code Description:

Cylinder 5 Misfire Detected

  1. Interpretation:

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

  1. 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
  1. 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
  1. 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

  1. Code Description:

Cylinder 6 Misfire Detected

  1. Interpretation:

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

  1. 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
  1. 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
  1. 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

  1. Code Description:

Misfire Detected On Startup (First 1000 Revolutions)

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • The engine lacks power
  • It is rough idle
  1. 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
  1. 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

  1. Code Description:

Ignition/Distributor Engine Speed Input Circuit Malfunction

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • The engine lacks power
  • The engine misfires, hesitates and stumbles
  • Engine cranks but it don’t start
  1. 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.
  1. 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

  1. Code Description:

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

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light may turn on
  • The engine may also lose power
  1. 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
  1. 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

  1. Code Description:

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

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light may come on
  • Fluctuation in RPM and loss of engine power
  1. Potential Causes:
  • The sensor in-circuit bank 1 may be defective
  • Open or short in the wiring to the sensor
  • Bad PCM
  1. 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

  1. Code Description:

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

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light turns on
  • Irregular RPM
  • The engine pings when accelerating
  • Loss of power
  • Knocking sound coming from the engine compartment
  1. 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
  1. 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

  1. Code Description:

Knock Sensor 2 Circuit Low Input (Bank 2)

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light may come on
  • Fluctuation in RPM and loss of engine power
  1. Potential Causes:
  • The sensor in-circuit bank 2 may be bad
  • Open or short in the wiring to the sensor
  • Bad PCM
  1. 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

  1. Code Description:

Crankshaft Position Sensor A Circuit Malfunction

  1. 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.

  1. Key Signs:
  • Check Engine Light comes on
  • The engine may fail to start
  • Car may run rough
  1. 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
  1. 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

  1. Code Description:

Crankshaft Position Sensor A Circuit Range/Performance

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • Intermittent stalling
  • The engine may fail to start
  • Irregular misfire
  1. 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
  1. 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

  1. Code Description:

Camshaft Position Sensor Circuit Malfunction

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light turns on
  • The engine may fail to start
  • Car may run rough
  • Rough idle
  • There is misfire
  1. Potential Causes:
  • Bad CPS
  • Open or short in CPS wiring
  • Faulty CKP sensor
  • A failed PCM
  1. 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

  1. Code Description:

Camshaft Position Sensor Circuit Range/Performance

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light may come on
  • Poor fuel economy
  1. Potential Causes:
  • Faulty CPS
  • Open or short in CPS wiring
  • Bad reluctor wheel
  • Interference in CPS wiring (from spark plug)
  1. 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

  1. Code Description:

Camshaft Position Sensor A Circuit Malfunction (Bank 2)

  1. 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.

  1. Key Signs:
  • Check Engine Light comes on
  • Low engine power
  • Difficulty starting or no starting totally
  • Car runs rough and/or misfires
  1. Potential Causes:
  • Open, grounded or short wiring in CPS circuit of bank 2
  • Faulty CPS
  • Bad CKP sensor
  1. 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

  1. Code Description:

Ignition Coil A Primary/Secondary Circuit Malfunction

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • There is an engine misfire
  1. 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
  1. 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

  1. Code Description:

Ignition Coil D Primary/Secondary Circuit Malfunction

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • Engine misfire
  1. Potential Causes:
  • Short or open in the coil on plug (COP) driver circuit
  • Loose or broken connection at the coil
  • Bad COP
  • Failed PCM
  1. 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

  1. Code Description:

Exhaust Gas Recirculation Flow Malfunction

  1. Interpretation:

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

  1. Key Signs:
  • Heightened NOx emissions
  • Increased combustion temperatures
  1. 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
  1. 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

  1. Code Description:

Exhaust Gas Recirculation Flow Insufficient Detected

  1. Interpretation:

The PCM has determined an insufficient amount of EGR

  1. Key Signs:
  • Engine pinging when the car is at high speed or under load
  1. 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
  1. 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

  1. Code Description:

Exhaust Gas Recirculation Flow Excessive Detected

  1. Interpretation:

The PCM has discovered an excessive amount of EGR

  1. Key Signs:
  • Engine surging off idle
  1. 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
  1. Diagnostic Procedure:
  • Check DPFE sensor voltage to ensure it’s within the required range
  • If not change the sensor.

P0403

  1. Code Description:

Exhaust Gas Recirculation Circuit Malfunction

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • The engine may misfire when accelerated
  • It is rough idle
  1. 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
  1. Diagnostic Procedure:
  • Pull codes and freeze frame data to ascertain P0403 code
  • Inspect all the wiring and connections to EGR solenoid
  • Disconnect and examine EGR valve circuit for a short or open
  • Clear code and do test drive. If it comes back change solenoid

P0404

  1. Code Description:

Exhaust Gas Recirculation Circuit Range/Performance

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • The engine may idle rough
  • The engine may fail to idle
  • Car may fail emissions
  1. Potential Causes:
  • Open or short in reference, ground or PCM controlled circuit
  • Bad PCM
  1. 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

  1. Code Description:

Exhaust Gas Recirculation Sensor A Circuit Low

  1. 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.

  1. Key Signs:
  • Check Engine Light turns on
  1. Potential Causes:
  • Open or short in reference or ground circuit
  • Faulty EGR valve
  • Failed PCM
  1. 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

  1. Code Description:

Exhaust Gas Recirculation Sensor A Circuit High

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • May surge when you drive
  • May stall intermittently
  • Vehicle may fail emissions
  1. Potential Causes:
  • Defective EGR valve
  • Short or open in EGR wiring circuit
  • Debris build up in EGR valve and is holding it open
  1. 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

  1. Code Description:

Secondary Air Injection System Incorrect Flow Detected

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • The engine may hesitate when you accelerate
  1. Possible Causes:
  • Faulty air injection pump
  • Inspect valve is bad or missing
  • Worn out or leak in exhaust component
  1. 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

  1. Code Description:

Catalyst System Efficiency Below Threshold (Bank 1)

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • The engine doesn’t have power
  • Lower fuel economy
  1. 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
  1. 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

  1. Code Description:

Warm-Up Catalyst Efficiency Below Threshold (Bank 1)

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • The engine doesn’t have power
  • The engine may hesitate during acceleration
  1. Potential Causes:
  • Bad catalytic converter
  • Faulty O2 sensor, particularly downstream O2 sensor
  • Fouled up the spark plug
  1. 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

  1. Code Description:

Catalyst System Efficiency Below Threshold (Bank 2)

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • The engine may lack power
  • Poor fuel economy
  1. Potential Causes:
  • Bad O2 sensor
  • There is a leak in the exhaust system
  • Faulty catalytic converter
  1. 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

  1. Code Description:

Evaporative Emission Control System Malfunction

  1. Interpretation:

A part of the EVAP system is not working well

  1. Key Signs:
  • Check Engine Light may come on
  1. 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
  1. 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

  1. Code Description:

Evaporative Emission Control System Incorrect Purge Flow

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light may come on
  • There is a rough or erratic idle
  1. Potential Causes:
  • Bad or loose EVAP hoses
  • Faulty purge valve
  • The gas cap is loose, missing or damaged
  • Faulty or damaged Charcoal canister
  1. 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

  1. Code Description:

Evaporative Emission Control System leak Detected (small leak)

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light may come on
  • Poor fuel economy
  1. 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
  1. 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

  1. Code Description:

Evaporative Emission Control System Purge Control Valve Circuit Malfunction

  1. 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)

  1. Key Signs:
  • Check Engine Light may come on
  • The vehicle may have a lean condition
  1. 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
  1. 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

  1. Code Description:

Evaporative Emission Control System Vent Control Circuit Malfunction

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  1. Potential Causes:
  • Bad EVAP vent valve
  • There is a blockage in vent valve
  • Vent valve control circuit has an open or short
  1. Diagnostic Procedure:
  • Inspect all the wiring to vent valve
  • If the above doesn’t, then change vent valve

P0449

  1. Code Description:

Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  1. Potential Causes:
  • Circuit issue in the EVAP vent valve
  • Bad EVAP vent valve
  • Wiring issue in the EVAP vent valve
  1. 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

  1. Code Description:

Evaporative Emission System Pressure Sensor/Switch Low

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  1. 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
  1. 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

  1. Code Description:

Evaporative Emission Control System Leak Detected (large leak)

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light may turn on
  • Lower fuel economy
  1. Potential Causes:
  • Bad or loose EVAP hoses
  • The gas cap is loose, missing or worn out
  • Non-compatible gas cap
  1. 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

  1. Code Description:

Evaporative Emissions System – Small leak detected

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  1. 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
  1. 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

  1. Code Description:

Evaporative Emission Control System (EVAP) Leak Detected

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • Poor fuel economy
  • The smell of fuel in the exhaust
  1. Potential Causes:
  • The gas cap is either loose, damaged or missing
  • Loose, disconnected or damaged hose in the EVAP system
  • Damaged vacuum canister
  1. 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

  1. Code Description:

Evaporative Emission Control System Pressure Sensor High Input

  1. Interpretation:

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

  1. 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
  1. Potential Causes:
  • Faulty fuel level sensor
  • The issue with fuel level sensor circuit
  • Bad instrument cluster
  • Defective fuel tank
  1. 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

  1. Code Description:

Vehicle Speed Sensor Malfunction

  1. Interpretation:

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

  1. 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
  1. Potential Causes:
  • Damaged VSS
  • Wiring challenge in VSS circuit
  • PCM is not configured correctly for the tire size of the car
  1. 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

  1. Code Description:

Idle Control System RPM Lower Than Expected

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • There is rough idle due to lower idle speed
  1. 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
  1. 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

  1. Code Description:

Idle Control System RPM Higher Than Expected

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  1. 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
  1. 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

  1. Code Description:

Engine Oil Pressure Sensor/Switch Range/Performance

  1. 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

  1. Key Signs:
  • The oil pressure gauge may read too low or too high
  • Check Engine Light comes on
  • Oil pressure light may come on
  1. Potential Causes:
  • Oil level in the engine is too low
  • Defective wiring to oil pressure sensor
  • Oil pressure is too low
  • Dirty oil
  1. 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

  1. Code Description:

Engine Oil Pressure Sensor/Switch Low Voltage

  1. Meaning:

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

  1. Key Signs:
  • Check Engine Light comes on
  • The engine may stall during driving
  • Oil pressure gauge reads zero or low value
  • Oil pressure light comes on
  • The engine may fail to start
  1. Potential Causes:
  • A problem with the wiring in oil pressure sensor circuit
  • Faulty oil pressure sensor
  • Low oil level or blockage in the oil passage
  • Utilizing the wrong type of oil
  1. 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

  1. Code Description:

System Voltage Low

  1. 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.

  1. 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
  1. Potential Causes:
  • Faulty alternator
  • High resistance either in alternator-battery circuit, alternator-PCM circuit or both
  • Failed PCM
  1. Diagnostic Procedure:
  • Inspect whether the battery voltage is right
  • Confirm 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

  1. Code Description:

ECM/PCM Processor Fault

  1. Interpretation:

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

  1. Main Symptoms:
  • Check Engine Light comes on
  1. Potential Causes:
  • Defective PCM
  1. Diagnostic Procedure:
  • Re-flash PCM with updated software. If that doesn’t function change the PCM

P0700

  1. Code Description:

Transmission Control System Malfunction

  1. 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

  1. Key Signs:
  • Check Engine Light comes on
  • Transmission may exhibit challenges
  1. Potential Causes:
  • All transmission-linked challenges can trigger this code
  1. 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

  1. Code Description:

Transmission Range Sensor Circuit Malfunction (PRNDL Input)

  1. Interpretation:

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

  1. 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
  1. 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
  1. Diagnostic Procedure:
  • It normally needs replacing the TRS

P0715

  1. Code Description:

Input/Turbine Speed Sensor Circuit Malfunction

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • Transmission may fail to shift
  • Transmission shifts unpredictably
  • Failure in speedometer
  • Reduced fuel economy
  1. 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
  1. 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

  1. Code Description:

Output Speed Sensor Circuit Malfunction

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • Delayed shifts
  • Worn out speedometer
  1. Potential Causes:
  • Bad OSS
  • Faulty transmission fluid temperature sensor
  • Wiring issue in the OSS circuit
  1. 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

  1. Code Description:

Torque Converter Clutch Circuit Performance or Stuck Off

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • Lower fuel economy
  1. Potential Causes:
  • Shorted wire in transmission’s ground circuit
  • Internal short in TCC solenoid
  • Bad TCM
  1. 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

  1. Code Description:

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

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • The engine performs unpredictably upon startup
  • Poor vehicle power
  • Rough idling
  1. Potential Causes:
  • Bad MAF sensor
  • Wiring problem in MAF sensor circuit
  • Defective connector(s) in MAF system
  1. 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

  1. Code Description:

HO2S Insufficient Switching Sensor 1

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • Difficult starting
  • Poor fuel economy
  • Rough or erratic idling
  1. 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
  1. 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

  1. Code Description:

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

  1. Interpretation:

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

  1. 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
  1. 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)
  1. 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

  1. Code Description:

Random Cylinder Misfire Detected

  1. 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

  1. 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
  1. 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
  1. 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

  1. Code Description:

Unable To Bleed Up Fuel Tank Vacuum

  1. 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

  1. Key Signs:
  • Check Engine Light comes on
  • The engine may refuse to start
  1. Potential Causes:
  • Bad vent valve
  • Obstruction in vacuum lines
  • Faulty charcoal canister
  • Overfilling fuel tank
  1. 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

  1. 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

  1. 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

  1. Code Description:

EVAP Leak Detection Pump Pressure Switch Condition

  1. 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

  1. Key Signs:
  • Check Engine Light may come on
  • Lower fuel economy
  1. 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
  1. 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

  1. Code Description:

Throttle actuator control module/throttle actuator position performance

  1. 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

  1. Key Signs:
  • Check Engine Light comes on
  • Car may fail to accelerate
  • Irregular surging
  • Poor fuel economy
  1. Potential Causes:
  • Bad pedal position sensor
  • Open or short in circuit supplying power to pedal position sensor
  • Failed PCM
  1. 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

  1. Code Description:

Battery Power to Module Disconnected

  1. 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

  1. Key Signs:
  • Check Engine Light comes on
  1. Potential Causes:
  • Short in TCM harness
  • TCM was either replaced or disconnected
  • Recently disconnected battery
  • Bad TCM
  1. 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

  1. Code Description:

Post Catalyst Fuel Trim System Too Lean Bank 1

  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.

  1. Key Signs:
  • Check Engine Light comes on
  • Lower fuel economy
  • Unpredictable acceleration
  • Engine misfires
  • It is rough idle
  • May produce spark knock
  1. 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
  1. 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

  1. Code Description:

Post Catalyst Fuel Trim System Too Rich Bank 1

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • Engine lacks power
  • Lower fuel economy
  1. 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
  1. 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

  1. Code Description:

Throttle Actuator “A” Control Motor Circuit Range/Performance

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • The engine refuses to accelerate
  • Fixed idle speed
  1. Potential Causes:
  • Faulty TA-A
  • Open or short in TA-A circuit
  • Bad PCM
  1. 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

  1. Code Description:

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

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • Car may refuse to start
  • Car may stall
  • Bad acceleration
  1. Potential Causes:
  • The bad throttle position sensor
  • Faulty throttle body motor
  • Wiring or connector problem in throttle body motor circuit
  1. 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

  1. Code Description:

Cooling System Performance

  1. 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.

  1. 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
  1. 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
  1. 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

  1. Code Description:

O2 Sensor Signal Stuck Lean Bank 1 Sensor 1

  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

  1. Key Signs:
  • Check Engine Light comes on
  1. 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
  1. 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

  1. Code Description:

O2 Sensor Signal Stuck Rich Bank 1 Sensor 1

  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

  1. Key Signs:
  • Check Engine Light comes on
  1. 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
  1. 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

  1. Code Description:

O2 Sensor Signal Biased/Stuck Lean Bank 1 Sensor 2

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • Engine may run rough
  1. 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
  1. 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

  1. Code Description:

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

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • The engine may lack power
  • Engine valve train may be too noisy
  1. Potential Causes:
  • Clogged oil passages
  • Low oil pressure
  • Oil utilized is too thick
  • Rocker arm actuator has a built-up slug
  1. 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

  1. Code Description:

O2 Sensor Circuit Range/Performance Bank 1 Sensor 1

  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
  1. Key Signs:
  • Check Engine Light comes on
  • Lower fuel economy
  • Pathetic engine performance
  • Engine misfires
  1. 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
  1. 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

  1. Code Description:

EBCM Motor Relay Circuit Low When On

  1. Interpretation:
  • The Electronic Brake Control Module (EBCM) is sending an unpredictably low voltage signal
  1. Key Signs:
  • ABS warning light comes on
  • Check Engine Light may come on
  1. Potential Causes:
  • Shorted or open wire in EBCM harness
  • The bad electrical connection in EBCM circuit
  • Faulty EBCM
  1. 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

  1. Code Description:

Engine Signal 1

  1. Interpretation:

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

  1. Key Signs:
  • ABS warning light comes on
  • Check Engine Light comes on
  1. 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
  1. 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

  1. Code Description:

Right Front Wheel Speed Sensor Input Circuit Failure

  1. Interpretation:

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

  1. Key Signs:
  • ABS warning light comes on
  • Check Engine Light comes on
  1. 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
  1. 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

  1. Code Description:

Engine Control System Malfunction

  1. Interpretation:

The Electronic Control Unit (ECU) has failed

  1. Key Signs:
  • Check Engine Light comes on
  • Additional warning lights may emerge depending on which module is affected
  1. Potential Causes:
  • Faulty ECU
  • Defective controller(s) because of abnormal system voltages
  1. 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

  1. Code Description:

Torque Request Signal Denied

  1. Interpretation:

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

C1223

  1. Code Description:

ABS Control System Malfunction

  1. Interpretation:

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

  1. Key Signs:
  • ABS warning light comes on
  • Check Engine Light comes on
  1. Potential Causes:
  • Faulty ABS control module
  • Open or short in the ABS circuit
  • Bad ABS sensor
  1. 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

  1. Code Description:

Left Front Wheel Speed Sensor Input Signal Missing

  1. Interpretation:

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

  1. Key Signs:
  • ABS warning light comes on
  • Check Engine Light comes on
  1. 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
  1. 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

  1. Code Description:

Right Front Wheel Speed Sensor Input Signal Missing

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • ABS warning light comes on
  1. 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
  1. 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.
  • Reset code and conduct drive cycle, if it returns probe ABS system entirely

C1241

  1. Code Description:

Low Battery Positive Voltage

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • ABS warning light comes on
  1. 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
  1. 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

  1. Code Description:

Right Rear Height Control Sensor

  1. 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.

  1. 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
  1. 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
  1. 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

  1. Code Description:

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

  1. 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

  1. Key Signs:
  • Check Engine Light comes on
  • Car may refuse to start on one or few attempts
  • The key alarm may activate intermittently
  1. 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
  1. 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

  1. Code Description:

Control Module Communication Bus “A” Off

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • Instrument cluster indicator “light” on
  • Poor fuel economy
  • The engine doesn’t have power
  1. Potential Causes:
  • Open in the “A” CAN bus + or – circuit
  • Short to power or ground in “A” CAN bus circuit
  1. 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

  1. Code Description:

Lost Communication With Transmission Control Module

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • The vehicle doesn’t shift gears
  • Remains in one gear, usually 2nd or 3rd gear
  1. Potential Causes:
  • Open in CAN bus + or – circuit
  • Short to power or ground in either + or – CAN bus circuit
  • Bad TCM
  1. Diagnostic Procedure:
  • With a bidirectional scanner, 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

  1. Code Description:

Lost Communication With Throttle Actuator Control Module

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • No throttle response
  • Electronic throttle control light comes on or flashes
  1. Potential Causes:
  • Open in CAN bus + or – circuit
  • Short to power or ground in either + or – CAN bus circuit
  • Bad TAC module
  1. Diagnostic Procedure:
  • With a bidirectional diagnostic scan tool, control TAC module and view it if it responds. If it doesn’t probe it further
  • 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

  1. Code Description:

Lost Communication With Anti-Lock Brake System Control Module

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • ABS warning light comes on
  • TRAC or ESP/ESC (or both) warning light comes on
  1. Potential Causes:
  • Open in CAN bus + or – circuit
  • Short to power or ground in either + or – CAN bus circuit
  • Faulty ABS control module
  1. Diagnostic Procedure:
  • Using a bidirectional automotive scanner, control ABS control module and check if it responds. If it does not check it further
  • 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

  1. Code Description:

Lost Communication with Instrument Panel Control Module

  1. Interpretation:

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

  1. 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
  1. Potential Causes:
  • Open in CAN bus + or – circuit
  • Short to power or ground in either + or – CAN bus circuit
  • Bad IPC module
  1. Diagnostic Procedure:
  • With a 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

  1. 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
  1. 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

  1. Code Description:

Lost Wheel Distance

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • ABS warning light may come on
  1. 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
  1. Diagnostic Procedure:
  • With a bidirectional scanner, 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

  1. Code Description:

CAN Communication Bus Fault

  1. Interpretation:

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

  1. Key Signs:
  • Check Engine Light comes on
  • Car may refuse to start on one or few attempts
  • The key alarm may set off intermittently
  1. 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
  1. 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

  1. Code Description:

Left Side Restraints Sensor 2

  1. Interpretation:

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

  1. Key Signs:
  • Airbag warning lights may come on
  • Excessive illumination of airbag warning lights
  1. Potential Causes:
  • Open, short or broken wire in left side restraint sensor 2 harness
  • Faulty left side restraint sensor 2
  1. 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

  1. 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

  1. Code Description:

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

  1. Interpretation:

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

  1. Key Signs:
  • Airbag warning lights may come on
  • Excessive illumination of airbag warning lights
  1. 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
  1. 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

  1. Code Description:

Driver Airbag Module Short

  1. Interpretation:

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

  1. Key Signs:
  • The airbag warning light comes on
  1. Potential Causes:
  • Short in driver airbag’s harness
  • Issue with spiral cable
  • Worn out driver airbag
  • Problem with electrical connection in driver airbag
  1. 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

  1. Code Description:

Battery Voltage Low

  1. Interpretation:

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

  1. 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
  1. 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
  1. 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

  1. Code Description:

ECU Is Defective

  1. Interpretation:

The Electronic Control Unit (ECU) is not working

  1. Key Signs:
  • Check Engine Light comes on
  • Other warning lights may show up depending on which module is affected
  1. Potential Causes:
  • Bad ECU
  • Worn out controller(s) due to abnormal system voltages
  1. 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

  1. Code Description:

Occupant Classification System Fault

  1. Interpretation:

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

  1. Key Signs:
  • The airbag warning light comes on
  • Check Engine Light may come on
  1. Potential Causes:
  • Challenges in the occupant classification system
  • Problem with wiring in the right front seat
  • The issue with airbag sensor assembly center
  1. 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

  1. Code Description:

Battery Pack Voltage Out Of Range

  1. 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

  1. Key Signs:
  • ABS warning light comes on
  • Check Engine Light may come on
  1. Potential Causes:
  • Blown fuse in ABS
  • The issue in the charging system
  • Problem within ABS module connector
  • Faulty ABS module
  1. 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 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.

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