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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to prevent electrical shorts during the repair.
• Allow the engine to cool down before working on components.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, hose clamps, screwdriver set
• Visually inspect all vacuum hoses and connections for cracks or disconnections.
• Use a vacuum gauge to check for leaks; if necessary, replace damaged hoses.
• Tighten any loose clamps or connections.

3. Clean or Replace MAF Sensor

• Tools Required: MAF sensor cleaner (or isopropyl alcohol), soft brush
• Remove the MAF sensor from the intake duct.
• Spray the MAF sensor cleaner on the sensor elements; avoid touching them.
• Allow it to dry completely before reinstalling. If damaged, replace the MAF sensor.

4. Check and Replace Fuel Filter (if clogged)

• Tools Required: Fuel pressure gauge, wrench set, replacement fuel filter
• Connect a fuel pressure gauge to the fuel rail to check fuel pressure.
• If pressure is low, replace the fuel filter by:
  • Relieving fuel pressure from the system.
  • Disconnecting the battery.
  • Removing the old fuel filter from its mounting brackets.
  • Installing the new fuel filter, ensuring proper orientation.

5. Inspect and Clean Fuel Injectors

• Tools Required: Injector cleaning kit or replacement injectors
• Remove fuel injectors from the engine.
• Use an injector cleaning kit to clean or replace the injectors as necessary.
• Reinstall the injectors ensuring all O-rings are intact and lubricated.

6. Reassemble and Test

• Reconnect the battery.
• Start the engine and let it idle to check for any leaks or issues.
• Use the OBD-II scanner to clear the code and check if it reappears.