how to fix P0171 code in BMW 3 Series G20/G21 (2019-2024)

Solution

1. Preparation

• Gather tools and parts as listed below.
• Disconnect the negative battery terminal to ensure safety while working on the vehicle.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:

  1. Inspect all vacuum lines for cracks or disconnections.
  2. Use a smoke tester to detect hidden leaks if necessary.
  3. Replace any damaged hoses or gaskets.

• Tools Required: Vacuum line replacement kit, smoke tester (if needed).

3. Clean or Replace the MAF Sensor

• Sub-steps:

  1. Locate the MAF sensor in the intake system.
  2. Disconnect the electrical connector and remove the sensor.
  3. Clean the sensor with MAF cleaner spray and allow it to dry.
  4. If the sensor is damaged, replace it with a new unit.

• Tools Required: Torx screwdriver, MAF cleaner.

4. Check and Adjust Fuel Pressure

• Sub-steps:

  1. Connect the fuel pressure gauge to the fuel rail.
  2. Turn the ignition on (do not start the engine) and check the pressure reading.
  3. If pressure is below specifications, inspect the fuel pump and filter for issues. Replace as needed.

• Tools Required: Fuel pressure gauge.

5. Inspect and Test Fuel Injectors

• Sub-steps:

  1. Remove the fuel rail to access the injectors.
  2. Clean the injectors using an ultrasonic cleaner or replace them if they are clogged.
  3. Reinstall the fuel rail and ensure all connections are secure.

• Tools Required: Injector cleaning kit or replacement injectors.

6. Reconnect and Test

• Sub-steps:

  1. Reconnect the negative battery terminal.
  2. Start the engine and let it idle.
  3. Check for any stored error codes and ensure the P0171 code is cleared.

• Tools Required: OBD-II scanner for code clearing.