how to diagnose a P0171 code in my Volkswagen Golf Eighth Generation (2020-present)?

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery negative terminal to ensure safety.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  • Visually inspect all vacuum hoses for cracks or disconnections.
  • Use a smoke machine or carburetor cleaner to identify leaks.
  • Replace any damaged hoses or gaskets.

3. Clean or Replace MAF Sensor

• Sub-steps:
  • Locate the MAF sensor in the air intake duct.
  • Disconnect the electrical connector and remove the sensor.
  • Clean the MAF sensor with MAF cleaner (do not use other cleaners).
  • If damaged, replace the MAF sensor with a new one and reconnect it.

4. Check Fuel Pressure

• Sub-steps:
  • Connect a fuel pressure gauge to the fuel rail test port.
  • Turn the ignition to the "ON" position (do not start the engine) and note the pressure reading.
  • Compare the reading to manufacturer specifications (typically around 50-60 psi).
  • If pressure is low, inspect the fuel pump and filter for issues.

5. Inspect Fuel Injectors

• Sub-steps:
  • Remove fuel injectors from the fuel rail.
  • Check for clogs using a cleaning kit or replace if needed.
  • Reinstall injectors and ensure proper sealing.

6. Test Oxygen Sensors

• Sub-steps:
  • Locate the upstream oxygen sensor (before the catalytic converter).
  • Use a multimeter to measure voltage output while the engine is running (should fluctuate between 0.1V to 0.9V).
  • Replace the sensor if readings are outside specifications.