my BMW X3 F25 (2011-2018) has a check engine light with code P0171

Solution

1. Preparation

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

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 propane torch to identify any hidden leaks.
  3. Replace any damaged hoses or tighten loose connections as necessary.

3. Clean or Replace Mass Airflow Sensor

• Sub-steps:
  1. Remove the MAF sensor from the air intake duct.
  2. Clean the sensor with MAF cleaner and allow it to dry before reinstalling.
  3. If cleaning does not resolve issues, replace the MAF sensor with a new one.

4. Check and Adjust Fuel Pressure

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail test port.
  2. Turn the ignition to the ON position (do not start) and observe the pressure reading; it should match manufacturer specifications.
  3. If pressure is low, check the fuel pump and replace if necessary.

5. Inspect and Clean Fuel Injectors

• Sub-steps:
  1. Remove the fuel rail to access the injectors.
  2. Inspect injectors for clogs or leaks.
  3. Clean or replace injectors as required. Use injector cleaning solution for clogs.

6. Reconnect Battery and Clear Codes

• Reconnect the battery.
• Use the OBD-II scanner to clear the codes and reset the check engine light.