how to diagnose P0171 lean code in BMW 5 Series F10/F11 (2010-2017)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the vehicle is on a flat surface and use wheel chocks for safety.

2. Inspect and Repair Air Intake System

• Sub-steps:
  1. Remove the engine cover (if applicable) using a socket set.
  2. Visually inspect all hoses and connections in the air intake system for cracks or disconnections.
  3. Use a smoke machine or soapy water to detect vacuum leaks.
  4. Repair or replace any damaged hoses or components found.

3. Clean or Replace MAF Sensor

• Sub-steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Disconnect the electrical connector carefully.
  3. Remove the MAF sensor using a Torx or socket wrench.
  4. Clean the sensor with MAF cleaner spray (avoid touching the sensor element).
  5. Reinstall the MAF sensor and reconnect the electrical connector.

4. Check and Replace Fuel Pressure

• Sub-steps:
  1. Connect a fuel pressure gauge to the Schrader valve on the fuel rail.
  2. Turn the ignition key to the ON position without starting the engine and check the pressure (should be in the manufacturer’s specified range).
  3. If pressure is low, inspect the fuel pump and fuel filter for issues and replace as necessary.

5. Inspect and Test Oxygen Sensors

• Sub-steps:
  1. Locate the upstream oxygen sensor (usually near the exhaust manifold).
  2. Disconnect the electrical connector.
  3. Use a multimeter to test the sensor's voltage output while the engine is running; it should fluctuate between 0.1 and 0.9 volts.
  4. Replace the sensor if it does not meet specifications.

6. Test Fuel Injectors

• Sub-steps:
  1. Remove the fuel injector connectors.
  2. Use a multimeter to check the impedance of each injector; values should be consistent with manufacturer specifications.
  3. If injectors are clogged, consider using a fuel injector cleaning kit or replacing them.