What Does P0172 BMW Error Code Mean? Learn Now!

For you to have a smooth and comfortable ride, the fuel and air mixture has to have the optimum fuel-to-air. However, if this ratio is not right, and you notice that your BMW’s check engine light is on, then you might be dealing with a P0172 BMW trouble code here. 

You may find yourself to be completely lost on what to do, but that’s how most people with little experience with automobiles react. Well, there’s no need to get worked up over clearing this code because we’re going to help you out by giving you all the crucial information that you need. 

P0172 BMW

What does P0172 BMW mean?

Since there are so many trouble codes associated with your BMW, it can be very easy to mix them up. The P0172 is a powertrain-related code, as it has to do with the functions of the engine and the drivetrain of your car.    

When there’s excess fuel in the combustion chamber and too little oxygen, it is said that the fuel mixture is too rich. This code is specifically triggered when the fuel in bank 1 becomes too rich. If you didn’t know, bank 1 is the part of the engine where the #1 cylinder is in. 

The presence of too much fuel and too little air/oxygen is detected by several sensors and then the engine control unit. When the engine control unit (ECU) gets the signal that the fuel mixture in bank 1 is too rich, the p0172 code is shown after an OBD2 scan. 

What Are the Symptoms?

Although there are several ways that you could tell whether or not you are dealing with a P0172 BMW code, not all of them can be detected by the average person. Here, in this section, we’ll be listing down some of the symptoms that are most easily detectable. Knowing the symptoms will also help you identify Ford P0172.

Strong Fuel Smell coming from the Exhaust

There are multiple reasons why you might notice this symptom in your car, and that includes a faulty fuel pressure sensor and an old transmission fluid. You will be able to detect this symptom because the smell is extremely foul and can make sitting in the car quite difficult. 

Overconsumption of Fuel

When the fuel mixture becomes too rich, your engine will end up using more and more fuel. The direct consequence of this is poor fuel economy, which we all hate because it just means more money has to be taken out of your pocket to buy fuel. However, the p0022 ford f150 camshaft over retarded issue can have the same impact. So, you can’t take it as a decisive sign.

Rough Idle

With powertrain issues, the rough idle symptom has to be one of the most common ones. It means that your car will shake when vibrating, and if you experience it you should immediately do an OBD2 scan. 

Misfiring of the Engine

You will know that your engine has misfired when you feel strong to moderate vibrations from the engine of the vehicle. In this exact case, it occurs the excessively rich fuel mixture makes some of the cylinders of the engine unable to produce power.

Hesitation of Engine and Lack of Power

Because of the rich fuel mixture, the engine is unable to produce the amount of power it would in its normal state. This drop of power can be felt easily, and the hesitation of the engine while accelerating will make your engine feel much weaker. 

Possible Causes for P0172 BMW

The P0172 could be displayed on your OBD2 scanner for a wide range of issues, and in some cases, there could be more than one issue triggering it. Even if you don’t do the diagnosis by yourself, it can be very helpful to know the possible causes of this code. It can help you monitor what the mechanic is doing and prevent you from being scammed by anyone. 

  • Dirty or defective mass airflow sensor that overstates the volume of air getting into the engine which results in the actual mixture being too rich. 
  • Malfunctioning air-fuel ratio sensor
  • Low fuel pressure due to weak fuel pump
  • Blocked fuel filter
  • Vacuum leaks in the PCV hose, intake manifold gasket, or vacuum hose
  • Leak in the Exhaust
  • Broken heated oxygen sensor

How to Diagnose P0172 BMW

How to Diagnose P0172 BMW

The first step to clearing the P0172 code is to diagnose it thoroughly to find what repairs have to be done. This process requires a great deal of patience as you will have to check all of the possible causes of this code. More importantly, you need to have hands of great experience in this matter or else you’ll only be left with more repairs and replacements because of your mess-ups. 

Hence, it’s always best to make a mechanic complete the diagnosis for you. We won’t be telling you in detail exactly how to diagnose this code because your mechanic will know what tests to run and what to check.

You should ensure that the mechanic checks all the parts prone to vacuum leaks and exhaust leaks. Next, you want them to inspect some of the sensors, such as the air-fuel ratio sensor, oxygen sensor, and mass airflow sensor to see if they’re faulty or not. The fuel pump should also be checked because, as we have mentioned, if it is weak, then the fuel mixture in bank 1 could get too rich.

Cost of Diagnose

Since diagnosing the P0172 code can be a complicated process, it will cost you some money. However, it won’t be really expensive either. This depends on the labor rate of the shop. Most highly experienced mechanics will charge you just about $100 or so. You may get some good mechanics to do it for a little cheaper, while others can charge you almost double for no reason. 

How to Fix P0172 BMW

The things you will have to get done to clear the P0172 code will depend on what issues you find during the diagnosis. As your mechanic will be doing the repairs and replacements for you, we won’t be talking about how to do them. Instead, we have some advice for you to follow when the professional is making the fixes. 

There are some fraudulent mechanics out there who will tell you that your car parts need to be replaced just for the sake of earning more money. To prevent being scammed like this, check whether their claims are true or not by being there during the tests. Also, after the repairs or replacements that the mechanic has done, ensure that they run an OBD2 scan to check whether the code has cleared yet. You don’t want to bring your BMW home only to see the code is still there. 


After reading our thorough and informative article on P0172 BMW, we hope you’re a little less confused than you were in the beginning. Even if you haven’t faced this issue yet, we would still suggest you learn all the information that we have provided just in case you encounter this problem in the future!

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