What Is BMW P0171 Code? [A Comprehensive Guide] 2024

Have you encountered the diagnostic trouble code (DTC) P0171 on the dashboard of your BMW vehicle while driving peacefully on the road? You’re looking to fix the error code to prevent the car from further internal damage that can impact the engine performance. 

Promptly addressing and fixing the BMW p0171 code is crucial because it can result in poor engine performance, rough idling, and reduced fuel efficiency if left unchecked and not diagnostics promptly.

In this guide, I will assist you in fixing the p0171 BMW code, understanding what it means, the most common symptoms to identify the issue early, the causes behind the fault, and potential solutions you must follow to solve the problem and ride safely. So, let’s clear your BMW’s dashboard from warning codes.

Understanding the BMW P0171 Code

The BMW code p0171 indicates a potential issue, “System Too Lean (Bank 1),” which is detected by the engine control module (ECM) on the first bank of cylinders. The ECM continuously monitors the air-fuel ratio to ensure smooth engine working, and different sensors, such as the Mass Air Flow and Oxygen sensor, deliver data to the ECM to make real-time decisions on fuel delivery, air intake, fuel injection, and ignition timings.

When any of the intake system components become faulty, fail to function, and start malfunctioning, it can cause unbalancing of the air-fuel ratio and force the ECM to trigger the code P0171 on the dashboard.

Symptoms of the P0171 Code BMW

After triggering the p0171 code, you might notice the following common symptoms, which indicate the presence of a fuel trim system that is too lean in Bank 1 of BMW. If addressed promptly, these signs will help you identify the problem and protect the vehicle from severe critical damage. 

Check Engine Light

The first and most obvious sign of the p0171 error code fault is the check engine light (CEL) illumination on the BMW’s dashboard. Look at the screen and see the CEL flashing, which means the ECM has detected the issue and triggered the warning light to inform the driver about the problems.

Reduced engine power

Due to too much air and insufficient fuel causing a lean mixture, you might experience poor acceleration while driving, and the vehicle will start reacting unresponsively and sluggishly. The engine needs the right fuel and air to work, and when the air-fuel ratio exceeds the acceptable limit, it will result in lean conditions, leading to reduced engine power.

Increased fuel consumption

The lean air-fuel condition can cause a comprehensive increase in fuel consumption that might force you to refuel more frequently. If you notice a sudden decrease in fuel efficiency, it points towards a potential issue in the intake system that the failed component may cause.

Rough idle or stalling

Another common sign that indicates the system’s too-lean bank1 condition is rough idling or stalling, which can be noticed when the engine is cold, and it struggles to maintain a steady idle or might stall out. If you experience uneven idling and excessive vibrations could be caused by a worn-out PCV valve, fuel injector, fuel pump, and other intake system components.

Engine misfires

You may experience jerking and hesitation during acceleration due to insufficient fuel in the engine combustion chamber, causing the engine to misfire.

Moreover, you can watch the below video if you don’t want to read the content:

How to Fix the P0171 Code in BMW

If you have noticed the above signs in your BMW, fixing the code ASAP is crucial. Here are the solutions you can follow to resolve the BMW p0171 code.

Vacuum leaks checking

The most common cause behind the triggering of BMW code p0171 is the vacuum leaks that occur when any of the intake system components, such as manifold gaskets, vacuum hoses, and intake manifold, are damaged or worn out, allowing the extra air to enter into the engine and making the system too lean bank1 of the engine. Inspect the components for any signs of damage or failure to function if anyone is found faulty, and repair or replace them to prevent excessive air from entering the engine.

MAF sensor inspection

Carefully inspect the mass air flow (MAF) sensor to see whether it’s functioning correctly or has become faulty. If it is found to be dirty or faulty, then clean it with a sensor cleaner. If cleaning doesn’t resolve the issue and code p0171 BMW is still blinking; you must replace the dirty MAF sensor and use a new one to fix the error.

Replace Faulty Oxygen Sensors

Test the oxygen sensor with the help of a diagnostic scanner tool to search for o2 sensor-related error codes. If the sensor is found to be malfunctioning, faulty, or too old, sending incorrect readings to ECM, then replacement of the O2 sensor should be done timely to restore the air-fuel mixture readings sent by the sensor.

Air filter replacement

Although the air filter is not a commonly reported culprit of the p0171 BMW code, it can also cause more air to enter the engine. Inspect and look at the air filter condition. Replace it if it’s dirty, clogged, or too old. Replacement of the air filter might also fix the issue it is causing due to the MAF sensor or air filter.

Inspect and Clean Fuel Injectors

Check all the fuel injectors for any signs of wear or malfunctioning symptoms. Clean the fuel injectors with the help of a fuel system cleaner and then verify whether the fault is fixed or not. If, after cleaning, the issue is still not resolved, then the replacement of fuel injectors must be completed to restore the fuel injection into the consumption chamber.

Fuel pressure checking

Inspect the components, such as the fuel filter, fuel pressure regulator, and fuel pump, to check the fuel pressure meets the manufacturer’s recommended specifications. Sometimes, when any of these components become faulty, the fuel pressure will be affected, which can cause low fuel delivery into the bank1. If any part is malfunctioning or defective, replace it to regulate fuel pressure.

PCV system checking

The positive crankcase ventilation (PCV) valve can also impact the air-fuel ratio and trigger the warning code bmw p0171 on the dashboard. Check and replace the PCV valve if it’s not functioning correctly.

Vehicles Most Prone to P0171 Issues

Here’s the breakdown of the most commonly reported car brands, the p0171 code of which is frequently experienced by the owners of different models. It’s not a problem affecting only BMW vehicles as it also triggers on other brands.

Seeking for professional diagnosis

However, after following the above solutions, your issue is resolved. However, if it persists, there’s a possibility that some critical issue is causing it that needs professional diagnosis to identify and address. Consult an experienced certified technician or mechanic specializing in fixing BMW issues for a more in-depth code diagnosis. He will resolve the problem easily because they have advanced equipment that helps detect faults in less time, which helps fix the p0171 new code.

How much does it cost to fix the bmw p0171 code?

It’s difficult to tell the exact price you can expect to pay while taking mechanic service to fix the code p0171 BMW. However, it depends upon the type of issue and component causing the problem, the vehicle’s make and model, the geographic locations where you’re getting service, and the complexity of the issue. The chart below contains the essential information about the replacement cost price of each component that you might have to replace.

In A Nutshell

The BMW p0171 code triggers when the engine control module detects a too-lean mixture of air-fuel ratio in bank1 of the engine. Timely addressing and fixing the p0171 BMW code is crucial to prevent further engine damage. After understanding the common signs, causes, and solutions to perform, you can make informed decisions and take a systematic approach to resolving the problems. 

However, when malfunctioning or faulty, inspection and replacement of defective components such as fuel injectors, PCV valves, fuel pumps, vacuum lines, and sensors are mandatory. In conclusion, seeking professional help will be a good decision if the issue is critical and complex.

Frequently Asked Questions

What does the BMW P0171 code mean?

The P0171 code indicates that the engine’s air-fuel mixture is too lean on Bank 1, meaning there’s too much air and insufficient fuel.

Can I drive my BMW with a P0171 code?

While you can drive with the P0171 BMW code, driving for only a short period is recommended as it can lead to poor engine performance, increased fuel consumption, rough idle, poor acceleration, engine misfires, and potential engine damage.

What are the common symptoms of a P0171 code in a BMW?

The most common signs of code p0171 in a BMW include the Check Engine Light, rough idle, decreased fuel efficiency, engine hesitation or stalling, reduced engine performance, and possible misfires.

How do I fix the P0171 code on my BMW?

To fix the p0171 code, you must perform these inspections, repairs, and replacements, such as checking for vacuum leaks, cleaning or replacing the MAF sensor, inspecting fuel injectors, replacing faulty O2 sensors, checking fuel pressure, and ensuring no exhaust leaks.

What causes the P0171 code in a BMW?

Common causes include:

• Vacuum leaks.
• A faulty Mass Air Flow (MAF) sensor.
• Clogged fuel injectors.
• Bad oxygen sensors.
• Fuel delivery issues.
• Faulty fuel pump.
• Damaged PCV valves.
• Exhaust leaks.
• PCV valve problems.