my BMW 3 Series G20/G21 (2019-2024) keeps throwing P0171 code, what does it mean?

Solution

1. Preparation

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

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  • Visually inspect all vacuum hoses for cracks or disconnections.
  • Use a smoke machine or propane torch to identify leaks.
  • Replace any damaged hoses or gaskets as needed.
• Tools Required: Smoke machine, hose clamps, replacement hoses.

3. Clean or Replace MAF Sensor

• Sub-steps:
  • Disconnect the MAF sensor connector.
  • Remove the MAF sensor from the air intake duct.
  • Clean the MAF sensor with MAF cleaner (do not touch the sensor element).
  • Reinstall the MAF sensor and reconnect the connector.
• Tools Required: Torx screwdriver, MAF cleaner.

4. Test Fuel System

• Sub-steps:
  • Connect a fuel pressure gauge to the fuel rail.
  • Turn the ignition to the ON position (do not start the engine) and check the fuel pressure.
  • If pressure is low, check the fuel pump and filter for blockages or failures.
  • Replace the fuel filter if necessary and ensure the fuel pump is functioning correctly.
• Tools Required: Fuel pressure gauge, basic hand tools.

5. Inspect and Test Oxygen Sensors

• Sub-steps:
  • Locate the upstream oxygen sensor(s) and disconnect the wiring harness.
  • Use a multimeter to test the sensor's resistance and voltage output.
  • Replace any faulty oxygen sensors.
• Tools Required: Multimeter, wrench set.