why does my BMW 5 Series G30/G31 (2017-2024) have a check engine light for P0171

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the vehicle's battery to ensure safety while working on electrical components.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses for cracks or disconnections.
  2. Use smoke test or carburetor cleaner to identify leaks around intake manifold and hoses.
  3. Replace any damaged hoses or gaskets found during inspection.
• Tools Required: Smoke machine (if using smoke test), carburetor cleaner, basic hand tools.

3. Clean or Replace MAF Sensor

• Sub-steps:
  1. Disconnect the MAF sensor electrical connector.
  2. Remove the MAF sensor from the air intake duct.
  3. Clean the MAF sensor with MAF cleaner spray or replace if damaged.
  4. Reinstall the MAF sensor and reconnect the electrical connector.
• Tools Required: MAF cleaner, screwdriver, torque wrench (if applicable).

4. Check Fuel Pressure

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail.
  2. Turn the ignition key to the "ON" position without starting the engine and check for proper fuel pressure.
  3. Start the engine and monitor fuel pressure; it should remain within specified range.
  4. If pressure is low, inspect the fuel pump and filter for issues.
• Tools Required: Fuel pressure gauge.

5. Inspect and Test Fuel Injectors

• Sub-steps:
  1. Remove the fuel rail to access the injectors.
  2. Inspect each injector for clogs, leaks, or electrical issues.
  3. Clean or replace any faulty injectors as needed.
• Tools Required: Injector cleaning kit, basic hand tools.

6. Test Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors.
  2. Use a multimeter to test the voltage output of the sensors while the engine is running.
  3. Replace any sensor that is not operating within specified parameters.
• Tools Required: Multimeter.