what does it mean if my BMW 3 Series G20/G21 (2019-2024) is showing code P0171?

Solution

1. Preparation

• Gather tools: OBD-II scanner, fuel pressure gauge, multimeter, socket set, cleaning supplies.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Repair Air Intake System

• Check all intake hoses and connections for cracks or loose fittings.
• Tighten or replace any damaged hoses as necessary.
• If leaks are found, replace with OEM parts to ensure proper fit and function.

3. Fuel System Inspection

• Connect a fuel pressure gauge to the fuel rail.
• Start the engine and check that the fuel pressure is within specifications (typically around 50-60 psi for most BMWs).
• If pressure is low, check the fuel pump and fuel filter for clogs; replace if necessary.

4. MAF Sensor Cleaning/Replacement

• Locate the MAF sensor in the air intake duct.
• Disconnect the electrical connector and unscrew the MAF sensor.
• Clean the sensor using MAF sensor cleaner; do not use other cleaners.
• If cleaning doesn’t resolve the issue, replace the MAF sensor with an OEM part.

5. Throttle Body Cleaning

• Remove the throttle body from the intake manifold.
• Clean the throttle body using throttle body cleaner and a soft brush.
• Reinstall the throttle body and ensure all gaskets are in good condition before reassembly.

6. Oxygen Sensor Check

• Use a multimeter to test the voltage output from the oxygen sensor.
• If readings are outside normal range (0.1-0.9 volts for a narrowband sensor), replace the sensor.