how to fix the P0171 code on my BMW 3 Series E90/E91 (2005-2012)?

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the negative battery terminal to ensure safety.
• Allow the engine to cool if it has been running.

2. Inspect and Replace Air Intake Components

1. Inspect Hoses and Manifold:
   • Visually check all air intake hoses and the intake manifold for cracks or loose connections.
   • Tighten or replace any damaged hoses.
2. Replace the MAF Sensor (if needed):
   • Remove the MAF sensor from the air intake duct.
   • Clean the MAF sensor using MAF cleaner or replace it if damaged.
   • Reinstall the MAF sensor securely.

3. Fuel System Check

1. Check Fuel Pressure:
   • Connect a fuel pressure gauge to the fuel rail.
   • Turn the ignition to the ON position (do not start the engine) and check the fuel pressure reading.
   • If pressure is below specifications (check manufacturer specs), inspect the fuel pump and filter.
2. Inspect and Clean Fuel Injectors:
   • Remove the fuel injectors from the fuel rail.
   • Clean injectors using a specialized cleaning kit or replace if clogged or leaking.
   • Reinstall the injectors ensuring proper sealing.

4. Oxygen Sensor Inspection

1. Inspect Oxygen Sensors:
   • Check the wiring and connectors for any damage or corrosion.
   • Replace any faulty oxygen sensors as required.

5. Reset the Engine Control Module (ECM)

1. Clear the Error Code:
   • Use the OBD-II scanner to clear the P0171 code from the ECM.
   • Reconnect the negative battery terminal.