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

Solution

1. Preparation

• Tools Required: OBD-II scanner, vacuum gauge, MAF cleaner, fuel pressure gauge, socket set, torque wrench, multimeter.
• Park the vehicle on a level surface and ensure the engine is off. Disconnect the battery before starting work.

2. Inspect and Repair Vacuum Leaks

• Visually inspect all vacuum hoses and connections for signs of wear or damage.
• Use a vacuum gauge to check for proper readings; if low, locate and repair any leaks.
• Replace any damaged hoses or connections with OEM parts.

3. Clean or Replace MAF Sensor

• Locate the MAF sensor in the air intake system.
• Disconnect the electrical connector and remove the MAF sensor using the appropriate socket.
• Clean the sensor with MAF cleaner. Allow it to dry completely before reinstallation.
• If damaged, replace the MAF sensor with a new one.

4. Check and Adjust Fuel Pressure

• Connect the fuel pressure gauge to the fuel rail test port.
• Turn the ignition to the "ON" position (do not start the engine) and observe the pressure reading.
• If the pressure is below specifications, check the fuel pump and filter. Replace them if necessary.

5. Inspect and Test Fuel Injectors

• Disconnect the fuel rail and inspect the injectors for clogs or leaks.
• Perform a flow test on each injector to ensure they are delivering the correct amount of fuel.
• Replace any faulty injectors with new ones.

6. Check Oxygen Sensor Functionality

• Use a multimeter to check the voltage output of the upstream oxygen sensor.
• Compare the readings to the manufacturer specifications; replace the sensor if readings are outside the normal range.