Troubleshooting Audi VW P0171 error code

Troubleshooting VW P0171 error code
Published by YOUCANIC Automotive Experts 
Last Updated Mar 4, 2019 

Are you trying to troubleshoot a P0171 error code on your German car? It is not unusual for check engine light to come on with a P0171 code.

This code affects many VW models and engines including the Polo 1.2, Passat 1.8T 2.0T, Jetta (Bora) 1.8T 2T 2.5, Golf 1.6, CC, Rabbit, GTI, Fehler, Beetle and Audi A3, A4, A6, TT.

What does Audi VW P0171 code mean? 

audi vw check engine light on p0171

Combustion engines are designed to run most efficiently when they have the correct ratio of air to fuel mixture.

That ideal ratio is 14.7 parts air to 1 part fuel. The P0171 error code is telling you that a lean condition exists, which means the ratio of air to fuel is off and there’s too much air in the system.

In this article, we’re going to break down what the symptoms, causes and possible solutions are for this error code so that you can get your Volkswagen properly functioning again. 

Symptoms

The P0171 error code can come with a lot of symptoms. First of all, the check engine light in your car will turn on. Any time this happens, it’s always a good idea to read the codes using an OBD2 scanner or even better to use a Diagnostic Scanner that can read Volkswagen fault codes

Another symptom may be that your car is having performance problems, such as some misfiring or a lack of power while accelerating.  

Your car also might have trouble idling at a stoplight or stop sign. Your vehicle may also experience some “coughing” noises while driving or sitting in traffic.  Another symptom may be that you have a hard time starting your car. Or it's even possible that the engine may die while you’re driving it. 

Common Causes 

As mentioned before, the VW P0171 error code is triggered on your car when a lean condition exists, meaning there is too much air and not enough fuel. This can be caused by a few different reasons. It’s important to figure out what the actual cause is before you jump to a solution because the different causes have different solutions.

And if you don’t fix the real problem, then you’re just going to keep getting this error. So make sure you check all of the possible causes to see what’s going on before you try to fix anything. 

vw  audi p0171 code

Mass Air Flow Sensor

One of the reasons you may be getting this error is due to a dirty or broken mass airflow sensor (MAF Sensor) which detects how much air is flowing into your engine. If this isn’t working properly, more air may be getting into your engine that is being detected, causing the lean ratio that triggers a P0171 error. It may also be that the control module software needs to be updated. This is the software that helps regulate the air and fuel ratio in your engine.

audi vw check engine light on due to bad oxygen sensor

Oxygen Sensor

It is possible that VW Code P0171 is caused by a defective Oxygen sensor that is sending values that are out of range. A bad O2 sensor is less likely the cause. Check that there are no vacuum leaks before replacing this sensor. 

Vacuum Leaks 

Vacuum leaks are also common causes of this kind of error to be triggered in your car. If there are vacuum leaks, that means air is getting into your engine that can't be auto-detected and corrected by the machine sensors, so it causes the lean condition. A weak fuel pump or plugged fuel filter may also be a cause because the fuel is not getting into the engine in the right ratio. Dirty or plugged fuel injectors might cause this as well.

Possible Solutions 

mass air flow sensor

There could be a lot of possible solutions to this error code. Diagnosing what the cause of the error is first will help you determine which solution is right for your situation. Check all of your vacuum lines and hoses for leaks. If you find any, then replace them. You can also repair other intake leaks.

Replacing the PCV valve, EVAP valve, and EGR valve can also fix this problem in some cases. If the issue is because of a problem with the mass airflow sensor try removing it and cleaning it or replacing it altogether. 

If the issue persists after you’ve replaced any leaky vacuums and cleaned the mass airflow sensor, it’s a good idea to run a fuel pressure test. This will tell you if you need to replace fuel pump, fuel filter or fuel pressure regulator.

These are the most common solutions for the P0171 error code. 

Frequently Asked Questions 

How severe is a VW P0171 error code?

Moderate, you can still drive for a little while after you get this error code. But driving with this error code for too long can cause serious problems in your engine. 

Is this error commonly misdiagnosed?

Yes, a lot of people will misdiagnoses this error code as a problem with the oxygen sensors, when really the issue could be something else like vacuum leaks.

Why does running “too lean” matter?

Cars that run too lean cause a lot of pollution. It can also cause your car to misfire or overheat, which is never a fun situation and can be harmful to your car.

What is the most common cause of the P0171 error code?

Intake leaks are the most common cause, but it is not the only cause so don’t jump to conclusions when you get this error. Be sure to check all common causes mentioned earlier to make sure you correctly diagnose the problem. 

 

Conclusion

Troubleshooting the VW P0171 error code on your car can be tricky. But now you know that this code indicates a lean condition in your combustion engine. This is due to the ratio of air to fuel is off of what it should normally be.

A lean condition means that there is too much air in the ratio. Knowing this and being aware of the common causes of this error code will help you find the best solution for fixing it.

Although this error code isn’t a severe threat to your car or your safety, you don’t want to be driving around with this issue for too long as it could cause issues and create more pollution.

Being aware of how to diagnose and properly treat the cause of this error code is essential to maintaining your car in perfect working order.

After reading this article, you now know what this error code means, how to diagnose the cause and how to solve the issue correctly.