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

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, fuel pressure gauge, multimeter, cleaning supplies (MAF cleaner), vacuum gauge.
• Steps:
  • Disconnect the vehicle’s battery to avoid electrical shorts.
  • Gather all necessary tools and parts for the repair.

2. Inspect and Repair Air Intake System

• Sub-steps:
  1. Visually inspect the air intake hoses and connections for any cracks or disconnections.
  2. Replace any damaged hoses or gaskets as needed.
  3. Use a vacuum gauge to check for leaks in the vacuum lines; replace any faulty lines.

3. Clean or Replace MAF Sensor

• Sub-steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Disconnect the electrical connector from the MAF sensor.
  3. Remove the MAF sensor using the appropriate socket.
  4. Clean the sensor with MAF cleaner and let it dry completely.
  5. Reinstall the MAF sensor and reconnect the electrical connector.

4. Check and Adjust Fuel Pressure

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail service port.
  2. Turn on the ignition (do not start the engine) to check the fuel pressure; it should be within the manufacturer’s specifications.
  3. If the pressure is low, check the fuel pump and fuel filter for issues and replace as necessary.

5. Inspect and Test Oxygen Sensor

• Sub-steps:
  1. Locate the upstream oxygen sensor (pre-cat).
  2. Use a multimeter to check the voltage output of the sensor while the engine is running; it should fluctuate between 0.1V and 0.9V.
  3. Replace the oxygen sensor if it is not functioning correctly.