how to fix a P0171 code on 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 down before beginning work.

2. Inspect and Repair Air Intake System

• Inspect Hoses

  • Check all vacuum hoses connected to the intake for cracks or disconnections.
  • Replace any damaged hoses.

• Inspect Intake Manifold

  • Remove the engine cover if applicable.
  • Inspect the intake manifold for leaks using a smoke test or visual inspection. Repair or replace as necessary.

3. Check and Replace Fuel Components

• Fuel Pressure Check

  • Connect the fuel pressure gauge to the fuel rail.
  • Turn the ignition to the ON position (do not start the engine) and check the reading against the manufacturer's specifications.
  • If pressure is low, check the fuel pump and fuel filter for issues. Replace as required.

• Inspect Fuel Injectors

  • Remove the fuel rail to access the injectors.
  • Clean or replace clogged injectors with a professional cleaning kit or replace them if faulty.

4. Test and Replace MAF Sensor

• Testing MAF Sensor

  • Disconnect the MAF sensor connector.
  • Use a multimeter to check the voltage output of the MAF sensor; compare it with spec values in the service manual.

• Replace MAF Sensor

  • If faulty, remove the MAF sensor from the air intake duct.
  • Install a new MAF sensor and reconnect the electrical connector.

5. Oxygen Sensor Inspection

• Check Oxygen Sensors
  • Inspect the upstream O2 sensor for proper function using a scan tool.
  • Replace if they are not responding within specified parameters.