why is my BMW 5 Series F10/F11 (2010-2017) giving me a P0171 code?

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down before starting work.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  • Visually inspect all vacuum hoses for cracks or disconnections.
  • Use a smoke machine or carburetor cleaner to identify leaks while the engine is running.
  • Replace any damaged hoses or gaskets.

3. Clean or Replace MAF Sensor

• Sub-steps:
  • Locate the MAF sensor in the air intake system.
  • Disconnect the electrical connector and remove the sensor using a Torx screwdriver.
  • Clean the MAF sensor with MAF cleaner spray; if heavily contaminated, replace with a new sensor.
  • Reinstall the MAF sensor and reconnect the electrical connector.

4. Check Fuel Pressure

• Sub-steps:
  • Connect a fuel pressure gauge to the fuel rail.
  • Turn the ignition key to the "On" position (do not start the engine) and check the fuel pressure reading.
  • Compare the reading to the manufacturer specifications (typically around 50-60 psi for many BMW models).
  • If the pressure is low, inspect the fuel pump and fuel filter for issues and replace as necessary.

5. Examine Engine Coolant Temperature Sensor

• Sub-steps:
  • Locate the engine coolant temperature sensor.
  • Use a multimeter to check the resistance of the sensor and compare it with specifications.
  • If the sensor is faulty, disconnect it and replace it with a new sensor.