What Does the Engine Code P0171 Mean?

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If your car is showing the P0171 engine code, your Engine Control Module has detected your air/fuel mixture ratio is too lean or there is a vacuum leak—this could be caused by a problem with the fuel injection system. 
While this code doesn’t pose an immediate danger, it is a serious issue. You should have your vehicle inspected as soon as possible to avoid wasting fuel and damage to the engine.   
Diagnostic trouble codes (DTCs) help drivers identify what’s wrong with the car’s engine. If you have an OBD-II code reader, you can identify which engine code is happening to you. Once you know the code, a skilled mechanic can diagnose the problem and point you to needed repairs.
Car insurance comparison and broker app Jerry can help you protect your car with expert information on DTCs and the best savings on car insurance. We’ve broken down the P0171 engine code so you know what it means, how to deal with it, and how much it costs to fix. 
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What does the engine code P0171 mean?

Definition: Fuel system is running too lean or there is a vacuum leak near a side of the engine (Bank 1)
The P0171 engine code indicates a problem with your car’s fuel injection system: the air-fuel mixture ratio is too lean. This affects how efficiently the fuel is being used. An incorrect air-fuel mixture ratio can also cause the vehicle to lose power and the engine to overheat.

How much will it cost to fix?

Running a diagnostic for a P0171 will usually cost you $75 to $150 per hour of labor.
However, the cost to fix this issue will vary greatly depending on what the root issue is. You may only need to replace the air filter and clean the airflow meter. However, if the P0171 code is combined with the P0174 code, you’ll likely need to repair a vacuum leak. 
Expect the repairs to cost as little as $50 or as much as $800.

What can cause the P0171 engine code?

If your car is showing the P0171 engine code, there is likely an issue with the fuel injection system
The fuel injection system controls the air-fuel mixture ratio before the fuel enters the combustion chambers. The fuel is atomized and mixed with the appropriate amount of clean air to keep the engine running optimally.
Other potential issues that could cause this engine code include: 
  • Intake air leaks
  • Faulty front heated oxygen sensor
  • Ignition misfiring
  • Exhaust gas leaks
  • Incorrect fuel pressure
  • Lack of fuel
  • Faulty mass airflow (MAF) sensor
  • Incorrect positive crankcase ventilation (PCV) hose connection

Common symptoms of the P0171 engine code

The only symptom you may see with this issue is the check engine light turning on. Other potential signs to watch for include: 
  • Excessive fuel consumption
  • Lack of power from the engine
  • Difficult to start the engine
If your fuel injection system is faulty and left unrepaired, your engine may start frequently overheating and the catalytic converter may be damaged. Don’t delay getting an inspection once you become aware of this code. 

How serious is the P0171 engine code? 

While the P0171 engine code doesn’t signal immediate issues, delaying repairs could lead to further damage to other vehicle components
Not only will you be wasting gas due to the lowered fuel efficiency, but the engine can get severely damaged from overheating, necessitating costly repairs.

Can I fix the P0171 engine code myself?

In some cases, you can fix the problem causing a P0171 engine code at home, but it’s vital to diagnose the issue correctly before you begin any repairs. 
Depending on the issue, you may have to:
  • Replace the MAF sensor
  • Replace the oxygen sensor
However, if you’re not sure what repairs your car needs, it’s better to bring your car to a professional to complete a thorough diagnostic inspection and requisite repairs.

Repairing the P0171 code

If you do decide to repair the P0171 code by yourself, there are two methods you can try:
  • Replacing the MAF Sensor
    • Remove the MAF sensor between the air filter and throttle body and inspect for dirty wiring
    • Spray clean the wires of the MAF sensor (do not get the sensor wet)
    • Reinstall the Dried MAF Sensor
  • Replacing the oxygen sensor
    • Remove oxygen sensor from the catalytic converter
    • Reinstall a new oxygen sensor 

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