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

Solution

1. Preparation

• Gather tools and parts needed.
• Disconnect the battery to ensure safety while working on electrical components.
• Allow the engine to cool before starting any work.

2. Clean the MAF Sensor

• Remove the MAF sensor from the intake duct.
• Use MAF sensor cleaner to spray the sensing elements, avoiding touching them directly.
• Allow the sensor to dry completely before reinstallation.

3. Inspect for Vacuum Leaks

• Visually check all vacuum hoses and connections for cracks or disconnections.
• Perform a smoke test if necessary to identify any hidden leaks.
• Replace any damaged hoses or gaskets found during the inspection.

4. Check Fuel Pressure

• Connect a fuel pressure gauge to the fuel rail.
• Turn the ignition to the "on" position without starting the engine and record the pressure reading. It should match the specifications in the service manual (typically around 50-60 psi).
• If low, check the fuel pump and filter for blockage or failure.

5. Inspect and Test Oxygen Sensors

• Check the wiring and connectors for the upstream oxygen sensor for any signs of damage.
• Use a multimeter to test the voltage output of the sensor while the engine is running. It should fluctuate between 0.1-0.9 volts.
• Replace the oxygen sensor if it fails the test.