how to troubleshoot BMW 3 Series G20/G21 (2019-2024) with P0171 code

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety during repairs.
• Allow the engine to cool down before starting work.

2. Inspect and Repair Air Intake System

• Tools Required: Socket set, screwdrivers, flashlight
• Sub-steps:
  1. Remove the engine cover (if equipped) to access the intake components.
  2. Inspect the air intake hose for any cracks or loose fittings and replace if necessary.
  3. Check the intake manifold gaskets for leaks and replace them if damaged.
  4. Ensure that the air filter is clean and properly seated; replace if dirty.

3. Test and Clean the MAF Sensor

• Tools Required: MAF cleaner, soft cloth
• Sub-steps:
  1. Disconnect the MAF sensor connector.
  2. Remove the MAF sensor from the air intake duct.
  3. Spray the MAF sensor with MAF cleaner and gently wipe with a soft cloth.
  4. Reinstall the MAF sensor and reconnect the plug.

4. Fuel System Inspection

• Tools Required: Fuel pressure gauge
• Sub-steps:
  1. Locate the fuel rail and attach the fuel pressure gauge.
  2. Turn the ignition to the "ON" position without starting the engine to check the pressure.
  3. Compare the pressure reading with the BMW specifications; replace the fuel pump if out of range.
  4. Inspect fuel injectors for clogs; clean or replace if necessary.

5. PCV System Check

• Tools Required: Vacuum gauge (optional)
• Sub-steps:
  1. Locate the PCV valve and inspect for blockages or cracks.
  2. Replace the PCV valve if it is stuck or damaged.
  3. Check hoses for leaks and replace if necessary.