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

Solution

1. Preparation

• Gather necessary tools: OBD-II scanner, multimeter, socket set, torque wrench, fuel pressure gauge, and cleaning supplies.
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses and connections for cracks or disconnections.
  2. Use a smoke machine or carburetor cleaner to identify leaks around the intake manifold and vacuum lines.
  3. Replace any damaged hoses or gaskets as necessary.
  4. Reconnect the battery terminal after repairs.

3. Clean and Test MAF Sensor

• Sub-steps:
  1. Remove the MAF sensor from the intake duct.
  2. Clean the MAF sensor using MAF cleaner spray; do not touch the sensing elements.
  3. Reinstall the MAF sensor and ensure all connections are secure.

4. Check and Repair Fuel System

• Sub-steps:
  1. Connect the fuel pressure gauge to the fuel rail and turn the ignition to the ON position (do not start the engine).
  2. Check the fuel pressure; it should be within the manufacturer's specifications (typically around 50-60 psi for most BMW models).
  3. If pressure is low, inspect the fuel pump and replace it if necessary.
  4. Remove and clean fuel injectors using a professional injector cleaning kit if they are clogged.

5. Inspect Oxygen Sensors

• Sub-steps:
  1. Use a multimeter to test the voltage output of the upstream oxygen sensor (should fluctuate between 0.1V and 0.9V).
  2. If the sensor is not functioning properly, replace it with a new one according to the manufacturer’s specifications.