how to diagnose P0171 lean code in Volkswagen Golf Seventh Generation (2013-2020)

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, fuel pressure gauge, socket set, and cleaning supplies.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses and gaskets for cracks or disconnections.
  2. Use a smoke machine or carburetor cleaner spray to detect leaks by observing changes in engine idle.
  3. Replace any damaged hoses or gaskets as necessary.

3. Clean or Replace MAF Sensor

• Sub-steps:
  1. Disconnect the MAF sensor’s electrical connector.
  2. Remove the MAF sensor from the intake duct.
  3. Clean the sensor using MAF cleaner (do not use other solvents).
  4. If cleaning does not resolve issues, replace the MAF sensor with a new one.

4. Test Fuel Pressure

• Sub-steps:
  1. Connect the fuel pressure gauge to the fuel rail.
  2. Turn the ignition key to the ON position (without starting) and record the pressure reading.
  3. Compare the reading to the manufacturer's specifications; replace the fuel pump if the pressure is low.

5. Inspect Fuel Injectors

• Sub-steps:
  1. Check for injector leaks by visually inspecting around the injectors.
  2. Use a multimeter to test the resistance of each injector (specifications will differ by model).
  3. Replace any faulty injectors as necessary.

6. Test Oxygen Sensors

• Sub-steps:
  1. Use a multimeter to check the voltage output of the upstream oxygen sensor while the engine is running (typically should fluctuate between 0.1 to 0.9 volts).
  2. Replace the oxygen sensor if it does not meet specifications.