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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before working on any components.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, hose clamps, socket set
• Inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
• Use a vacuum gauge to test for leaks; if found, replace damaged hoses or reattach loose connections.

3. Clean or Replace the MAF Sensor

• Tools Required: MAF cleaner, screwdriver
• Remove the MAF sensor from the intake duct.
• Spray MAF cleaner onto the sensor element to remove debris.
• Reinstall the MAF sensor and ensure it is secured properly. If defective, replace the MAF sensor.

4. Check Fuel Pressure

• Tools Required: Fuel pressure gauge
• Locate the fuel rail on the engine and connect the fuel pressure gauge.
• Turn the ignition to the "on" position without starting the engine and check for proper fuel pressure (usually specified in the service manual).
• If the pressure is low, check the fuel pump and filter for clogs or failures.

5. Inspect Fuel Injectors

• Tools Required: Fuel injector cleaning kit, socket set
• Remove the fuel rail and inspect the injectors for clogs or leaks.
• Clean the injectors using a fuel injector cleaning kit or replace them if necessary.
• Reinstall the fuel rail and ensure all connections are secure.

6. Test Oxygen Sensors

• Tools Required: Multimeter
• Disconnect the upstream oxygen sensor and test its voltage output while the engine is running.
• A healthy sensor should output a fluctuating voltage. Replace the sensor if it is out of specification.