how to fix P0171 lean code in BMW 3 Series G20/G21 (2019-2024)

Solution

1. Preparation

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

2. Inspect and Repair Air Intake System

• Tools Required: Screwdriver set, vacuum gauge, hose clamps.
• Inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
• Replace any damaged hoses and ensure all connections are secure.

3. Clean or Replace MAF Sensor

• Tools Required: MAF cleaner, soft cloth.
• Remove the MAF sensor from the air intake tube.
• Spray MAF cleaner on the sensor element and let it dry completely.
• Reinstall the MAF sensor, ensuring it is securely fastened.

4. Check Fuel Pressure

• Tools Required: Fuel pressure gauge.
• Locate the fuel rail and connect the fuel pressure gauge.
• Turn the ignition to the "ON" position without starting the engine and observe the pressure reading. It should typically be within the manufacturer's specified range (refer to service manual).
• If pressure is low, replace the fuel pump or filter as necessary.

5. Clean Throttle Body

• Tools Required: Throttle body cleaner, soft cloth, socket set.
• Remove the throttle body from the intake manifold.
• Clean the throttle plate and surrounding areas with throttle body cleaner.
• Reinstall the throttle body, ensuring a proper seal with a new gasket if required.

6. Inspect and Replace Fuel Injectors (if necessary)

• Tools Required: Injector puller tool, multimeter.
• Use a multimeter to test the resistance of each fuel injector.
• If an injector is found faulty, remove the fuel rail and replace the malfunctioning injector with a new one.
• Reinstall the fuel rail, ensuring all connections are secure.