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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is on a flat surface and secure with wheel chocks.
• Disconnect the negative terminal of the battery.

2. Inspect and Replace Leaky Hoses

• Sub-steps:
  1. Visually inspect all vacuum hoses for cracks or damage.
  2. Replace any damaged hoses with OEM specifications.
  3. Ensure all clamps are tightened securely.
• Tools Required: Pliers, replacement hoses, and clamps.

3. Clean Mass Air Flow Sensor

• Sub-steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Disconnect the electrical connector.
  3. Remove the sensor using a Torx screwdriver.
  4. Spray MAF cleaner on the sensing element (do not touch it) and allow it to dry.
  5. Reinstall the sensor and reconnect the electrical connector.
• Tools Required: Torx screwdriver, MAF cleaner.

4. Test and Replace Fuel Filter (if necessary)

• Sub-steps:
  1. Locate the fuel filter and relieve fuel pressure by loosening the fuel cap.
  2. Disconnect the fuel lines using a line wrench.
  3. Remove the filter and replace it with a new one.
  4. Reconnect the fuel lines and check for leaks.
• Tools Required: Line wrench, replacement fuel filter.

5. Check Fuel Pressure

• Sub-steps:
  1. Attach a fuel pressure gauge to the fuel rail.
  2. Turn the ignition to the ON position (do not start the engine) and note the pressure reading.
  3. Compare the reading with manufacturer specifications; if low, check the fuel pump.
• Tools Required: Fuel pressure gauge.

6. Clear Codes and Test Drive

• Sub-steps:
  1. Use the OBD-II scanner to clear the P0171 code.
  2. Test drive the vehicle to ensure the check engine light does not reappear.
• Tools Required: OBD-II scanner.