how to fix P0171 code in my BMW 5 Series G30/G31 (2017-2024)?

Solution

1. Preparation

• Gather tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
  2. Use a smoke machine or carburetor cleaner to locate hidden vacuum leaks by monitoring for changes in engine RPM.
  3. Replace any damaged hoses or gaskets identified during inspection.

3. Clean the Mass Air Flow (MAF) Sensor

• Tools Required: MAF cleaner spray
• Sub-steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Disconnect the electrical connector and remove the sensor from the duct.
  3. Spray the MAF cleaner directly onto the sensor element and let it dry completely.
  4. Reinstall the MAF sensor and reconnect the electrical connector.

4. Check and Adjust Fuel Pressure

• Tools Required: Fuel pressure gauge
• Sub-steps:
  1. Locate the fuel rail and attach the fuel pressure gauge to the Schrader valve.
  2. Turn the ignition on (do not start the engine) to check the fuel pressure. Refer to the specifications for the correct pressure range.
  3. If the pressure is low, inspect the fuel pump and replace if necessary.

5. Inspect and Clean Fuel Injectors

• Tools Required: Injector cleaner kit
• Sub-steps:
  1. Remove the fuel injectors from the fuel rail.
  2. Use an injector cleaning kit to clean each injector according to the manufacturer’s instructions.
  3. Reinstall the injectors and ensure they are seated properly.

6. Test and Replace Oxygen Sensors (if needed)

• Sub-steps:
  1. Use a multimeter to check the voltage output of the upstream oxygen sensor while the engine is running.
  2. If the sensor is not responsive or out of specification, replace it with a new one.
  3. Clear the error codes and perform a test drive to confirm the fix.