what causes the P0171 code in my BMW 5 Series G30/G31 (2017-2024)?

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shock.
• Ensure the engine is cool before working on it.

2. Inspect and Repair Air Intake System

• Sub-steps:
  1. Visually inspect all air intake hoses for cracks or loose connections.
  2. Tighten any loose clamps or replace damaged hoses.
  3. Clean the air filter, or replace it if it’s dirty.

3. Check and Repair Fuel System

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail.
  2. Turn the ignition to the "ON" position (without starting the engine) and check the fuel pressure.
  3. If the pressure is below specification, replace the fuel pump or fuel filter as needed.
  4. Inspect fuel injectors; clean or replace them if clogged or leaking.

4. Test and Replace MAF Sensor

• Sub-steps:
  1. Disconnect the MAF sensor electrical connector.
  2. Use a multimeter to test for the correct voltage output while the engine is running.
  3. If readings are outside the manufacturer’s specifications, replace the MAF sensor.

5. Inspect Engine Vacuum System

• Sub-steps:
  1. Use a vacuum gauge to check for vacuum leaks.
  2. If a leak is detected, replace any faulty vacuum hoses or components.
  3. Recheck the system for leaks after repairs.