how to fix P0171 code on my BMW 3 Series G20/G21 (2019-2024)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to ensure safety before working on electrical components.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Hose clamps, vacuum gauge, screwdriver.
• Sub-steps:
  1. Visually inspect all vacuum hoses for cracks or disconnections.
  2. Use a vacuum gauge to check for leaks; replace any damaged hoses.
  3. Tighten any loose clamps and ensure proper sealing at the intake manifold.

3. Clean or Replace the MAF Sensor

• Tools Required: MAF cleaner, small screwdriver.
• Sub-steps:
  1. Locate the MAF sensor in the intake duct.
  2. Disconnect the electrical connector and remove the sensor.
  3. Clean the MAF sensor using MAF cleaner; avoid touching the sensing element.
  4. Reinstall the sensor and reconnect the electrical connector.

4. Fuel System Inspection

• Tools Required: Fuel pressure gauge, socket set.
• Sub-steps:
  1. Connect the fuel pressure gauge to the fuel rail to check for the correct pressure.
  2. If the pressure is low, inspect the fuel pump and filter.
  3. Replace a clogged fuel filter if necessary and ensure the fuel pump is operational.

5. Verify Fuel Injector Operation

• Tools Required: Noid light tester, multimeter.
• Sub-steps:
  1. Use a noid light to check for signal at the fuel injectors.
  2. If no signal is present, test the wiring and connectors for faults.
  3. Replace any faulty injectors or wiring as needed.

6. Check Engine Coolant Temperature Sensor

• Tools Required: Multimeter.
• Sub-steps:
  1. Locate the engine coolant temperature sensor and disconnect it.
  2. Use a multimeter to test the resistance of the sensor against manufacturer specifications.
  3. Replace the sensor if readings are outside the acceptable range.