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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the vehicle battery to prevent electrical shorts.

2. Inspect and Repair Air Intake System

• Tools Required: Hose clamps, screwdriver, inspection light.
• Inspect all air intake hoses for cracks or loose connections.
• Tighten or replace any damaged hoses as needed.

3. Check and Clean MAF Sensor

• Tools Required: MAF cleaner, soft cloth.
• Locate the MAF sensor in the air intake path.
• Carefully disconnect the wiring harness.
• Remove the sensor and clean it using MAF cleaner. Allow it to dry completely before reinstalling.

4. Test and Adjust Fuel Pressure

• Tools Required: Fuel pressure gauge.
• Locate the fuel rail and attach the fuel pressure gauge.
• Start the engine and check the pressure against OEM specifications (typically around 50-60 psi for most BMWs).
• If pressure is low, inspect the fuel pump and replace if necessary.

5. Inspect and Test Fuel Injectors

• Tools Required: Injector cleaning kit.
• Remove the fuel injectors from the fuel rail.
• Use an injector cleaning kit to clean the injectors thoroughly.
• Reinstall the injectors and ensure they are securely connected.

6. Check and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench.
• Inspect the wiring and connectors of the oxygen sensors for damage.
• If faulty, replace the upstream oxygen sensor with a new one.
• Reconnect the wiring harness and ensure all connections are secure.