how to fix P0171 lean code in BMW 3 Series F30/F31 (2012-2019)?

Solution

1. Preparation

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

2. Inspect and Repair Air Intake System

• Tools Required: Socket set, screwdrivers, vacuum gauge
• Sub-steps:
  1. Remove the engine cover (if applicable) using the socket set.
  2. Inspect all vacuum hoses connected to the intake system for cracks or breaks; replace any damaged hoses.
  3. Check the intake manifold gasket for leaks; replace if necessary.
  4. Reconnect any loose connections and ensure all clamps are secure.

3. Clean or Replace MAF Sensor

• Tools Required: MAF cleaner, torx screwdriver
• Sub-steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Disconnect the electrical connector and remove the sensor using the torx screwdriver.
  3. Spray MAF cleaner on the sensor elements (do not touch them) and let it dry.
  4. Reinstall the MAF sensor and reconnect the electrical connector.

4. Check Fuel Pressure

• Tools Required: Fuel pressure gauge
• Sub-steps:
  1. Locate the fuel rail test port and remove the cap.
  2. Connect the fuel pressure gauge to the port.
  3. Turn the ignition key to the "ON" position (do not start the engine) and read the pressure on the gauge.
  4. Compare the reading with the specifications (typically around 50-60 psi); if low, inspect the fuel pump and filter.

5. Inspect Throttle Body

• Tools Required: Throttle body cleaner, socket set
• Sub-steps:
  1. Remove the intake duct connected to the throttle body.
  2. Inspect the throttle plate for carbon build-up; clean using throttle body cleaner.
  3. Ensure the throttle body operates smoothly without sticking.