code P0171

Trouble code P0171: Issue with fuel block for too much air

code P0171For cars, gasoline is used for spark ignited internal combustion of the engine. And this system is mainly used in diesel vehicles. The work of the ignited system is it injects fuel into the combustion chamber, and after that, it combines with air. The spark plug mixes the air and fuel for the ignited system. So this ratio is essential for every car. This measurement of air and fuel of gasoline maintains the performance of the controlling and tuning. Suppose there is any issue faced in there that causes exhaust emission pollution. The AFR utilizes minimum air to burn enough air in the engine to burn all gasoline on the fuel. When this system is too lean on Bank 1, your car faces the issue of trouble code P0171. 

Recommended Tools for Diagnosis

  • OBD-II Scanner
  • Fuel Pressure Gauge
  • Vacuum Gauge
  • Smoke Machine
  • Digital Multimeter
  • Inspection Light
  • Air Flow Meter

What is the meaning of the trouble code P0171?

The trouble code P0171 means the fuel system is weak in Bank System 1. When the engine block is not ideal, a car engine’s air-fuel ratio is not perfect. There are two issues. The first one is too much air or not so much fuel on the lines. It causes the P0172 code. Another one is extra air in the system that causes the P0171 trouble code. This happens when there is any leakage in the car’s vacuum, which allows extra oxygen into the line. And for this, there is not enough fuel to reach the engine to balance the ratio of air in there.

So, when bank 1 gets too lean an air and fuel mixture or vice versa, the system detects the error code P0171 or P0172. If you find the code from there and the user uses it for a long time, this also improves the engine’s performance, and the combustion temperature is higher than the ideal heat. 

What is the reason for the P0171 error code?

There are many reasons behind the error code P0171, and those are:

  • Leak in a vacuum,
  • Damaged fuel pump,
  • Clogged/blocked fuel filter,
  • Damaged fuel pressure regulator,
  • Fault in Powertrain control module or PCM.
  • Leak in the exhaust system,
  • The damaged oxygen sensor,
  • The blocked catalytic converter,
  • Defect in the injector,
  • Fault in air and fuel ratio sensor,
  • Defect in mass air flow sensor.

What are the symptoms of the error code P0171?

If you are a new car owner, you must notice some primary symptoms to ensure the issue is related to error code P0171. Let’s write down this below:

  • Illuminated or flashing check engine light,
  • Loss of power,
  • Rough at idle,
  • Stumble from the engine,
  • Misfiring on the engine,
  • Difficult to start the car engine,
  • White spark plug tips,
  • After someday, the engine may die,
  • If this code is stored in the car’s memory for a long time, it also damages the catalytic converter.

How serious is the error code P0171?

The seriousness of the error code P0171 is very dangerous. Because if a vehicle stores the code on its powertrain control module, it creates an issue in a car engine and simply decreases the running speed of the car. The problem mainly begins with maintaining the proper air/fuel ratio, and users face a significant waste of fuel and a lack of driving experience. So it’s imperative to repair the car as soon as possible and drive it safely.

How to diagnose the error code P0171?

To solve the issue, you just need to know how to diagnose the problem from the car. From DIY to the mechanic, they check the whole car system with an OBD scanner. After that, when they got the error code P0171, they checked the engine for any vacuum leaks on the vacuum gauge. And this leakage mainly creates a mechanical or hissing type sound, and this sound is audible after turning off the engine. 

After that, check the fuel pressure and MAF or mass air flow sensor with a fuel pressure gauge. To maintain the proper ratio of air/fuel, the vacuum, and the fuel pressure of the engine, every examination is done under the manufacturer’s specification. Most of this code was found after one of those two codes. 

If you don’t find the issue, the mechanic tries to perform two tests to find the case on the sensor or not. They also run the tests on the mass air flow sensor and oxygen sensor. But always follow the manual procedure. And at the end, if you still remain in the dark, then check whether the issue is the Powertrain control module or PCM or not. 

A professional car mechanic mainly uses all these, but if you are new and love to DIY, you did all these steps still but adequately find the error code on the dashboard, then you need help from a mechanic. You also read the car and OBD manual book. Sometimes it got many details of the many issues of the car. So if you get lucky, you can get the solution in there and do it yourself. It saves you some money and also time. 

Don’t make a Mistake!

As I told you before, people often don’t look after the mistake in the technical service bulletins for specific car models; sometimes, it contains the solution to a related issue. But if you don’t get the code-related help from there, go to talk to the professional. Without confirmation, don’t change any sensor or part of the car. It’s not going to help your issue. In addition to that, you end up wasting some money.

How to solve the error code of P0171?

There are some basic simple steps that need to be followed to clear the code from the car. And those are:

  • First, check if there is any leakage in the vacuum system, so use the vacuum pressure gauge, or listen to the hissing sound around the engine to examine the leakage. 
  • After that, ensure enough gasoline for the engine and use the vacuum gauge. And just like that, check the fuel filters and injectors to ensure the gauge is working well or not.
  • Then run a diagnostic to test the health and functionality of the oxygen sensor. If there is any issue, then you need to repair or replace this.
  • Check whether the fuel pressure regulator is working fine and if it’s damaged, change it as soon as possible.
  • If there is any issue in the fuel pump or filter, and it gets dirty, then at first, clean it as much as possible. If it doesn’t work after cleaning, then you need to change this to maintain the fuel/air ratio.

So at first, check the issue and then solve it in the proper way. But before you replace the sensor or filter or any part of there, ensure the fault is in there or not. Otherwise, you end up replacing the good device. And it’s just a waste of money and still has the car issue. 

Cost of repairing the error code P0171 from the car:

The diagnostic cost is divided into two ways: changing the device from the car and labor cost. And the price of these two things is variable in different places. But if the error code happens for minor issues, then you need around $100. But if you have a major issue, you need to change the damaged part of the engine. And the price of the damaged part depends on the device, and its total cost is around $150 to $900. But I suggest solving this issue as soon as you find it on the car dashboard. If you neglect this code, it may damage some sensors of the car. On the other hand, this also starts to damage the car engine. You also face uneasiness while driving the car with a hissing sound after turning off the engine. 


  • Are the bad spark plugs created for error P0171?

Not like that, mainly the vacuum leakage downstream from the MAF sensor or any defect on the MAF sensor is the main villain of this issue P0171.

  • Can the user drive the car with this error code P0171?

Most of the time, driving a car with this issue is really not a good experience. It made a hissing sound after turning off the car engine, and after neglecting the code for a long time, it also damaged the car engine.

  • Is the bad O2 sensor the reason for the error code P0171?

No, the issue is not directly related to error code P0171.

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