how to fix P0171 code in BMW 5 Series G30/G31 (2017-2024)?

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, fuel pressure gauge, basic hand tools, vacuum gauge.
• Disconnect the negative battery terminal to prevent electrical shock.
• Allow the engine to cool before starting work.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses for cracks or disconnections.
  2. Use a vacuum gauge to check for leaks; a reading below normal indicates a vacuum leak.
  3. Replace any damaged hoses or gaskets found during inspection.

3. Clean or Replace MAF Sensor

• Sub-steps:
  1. Disconnect the MAF sensor connector.
  2. Remove the MAF sensor from its housing using a screwdriver.
  3. Clean the sensor with MAF cleaner spray and allow it to dry completely.
  4. Reinstall the sensor and reconnect the wiring harness. If malfunctioning, replace the MAF sensor.

4. Check and Adjust Fuel Pressure

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail.
  2. Turn the ignition key to the "ON" position (do not start) to prime the fuel system.
  3. Check the fuel pressure reading; it should match the manufacturer specifications (usually between 50-60 psi).
  4. If pressure is low, inspect the fuel pump and filter for issues and replace as necessary.

5. Inspect and Test Fuel Injectors

• Sub-steps:
  1. Disconnect the fuel injector connectors.
  2. Use a multimeter to check the resistance of each injector; it should be within the manufacturer's specified range.
  3. If any injectors are out of range, replace them.
  4. Clean any clogged injectors using a specialized injector cleaning solution.

6. Check Oxygen Sensors

• Sub-steps:
  1. Use a multimeter to test the voltage output of the upstream oxygen sensor while the engine is running.
  2. The voltage should fluctuate between 0.1 to 0.9 volts. If the readings are static, replace the sensor.
  3. Clear the P0171 code using the OBD-II scanner after repairs.