how to fix P0171 lean code in BMW 5 Series G30/G31 (2017-2024)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the vehicle battery to ensure safety.
• Allow the engine to cool before beginning work.

2. Inspect for Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses for cracks or disconnections.
  2. Use a smoke tester to identify any hidden leaks in the intake manifold or vacuum lines.
  3. Repair or replace any damaged hoses or components.

3. Clean or Replace MAF Sensor

• Tools Required: MAF cleaner
• Sub-steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Disconnect the electrical connector and remove the sensor.
  3. Clean the sensor using MAF cleaner and let it dry.
  4. Reinstall the MAF sensor and reconnect the electrical connector.

4. Check and Adjust Fuel Pressure

• Tools Required: Fuel pressure gauge
• Sub-steps:
  1. Locate the fuel rail and connect the fuel pressure gauge.
  2. Start the engine and monitor the fuel pressure reading.
  3. If pressure is low, check the fuel pump and replace if necessary.
  4. If pressure is within specifications but still lean, proceed to check injectors.

5. Inspect Fuel Injectors

• Sub-steps:
  1. Remove the fuel rail to access the injectors.
  2. Inspect injectors for clogs or leaks.
  3. Clean injectors using a professional fuel injector cleaning kit or replace them if they are faulty.

6. Verify ECT Sensor Function

• Sub-steps:
  1. Locate the ECT sensor and disconnect the wiring harness.
  2. Measure the resistance using a multimeter at various temperature points.
  3. Compare readings to manufacturer specifications; replace the sensor if out of range.