how to fix P0171 code on Volkswagen Golf MK7 (2015-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the vehicle battery to ensure safety.
• Allow the engine to cool down before starting work.

2. Inspect for Vacuum Leaks

• Tools Required: Vacuum gauge, smoke machine (optional)
• Check all vacuum lines and connections for cracks or disconnections.
• Use a smoke machine to detect leaks if necessary.
• Repair or replace any damaged hoses or gaskets.

3. Clean or Replace MAF Sensor

• Tools Required: Torx screwdriver, MAF cleaner
• Disconnect the MAF sensor wiring harness.
• Remove the MAF sensor from the air intake tube.
• Clean the sensor using MAF cleaner; do not touch the sensor element.
• If cleaning does not resolve the issue, replace the MAF sensor with a new one.

4. Check and Adjust Fuel Pressure

• Tools Required: Fuel pressure gauge
• Locate the fuel pressure test port on the fuel rail.
• Connect the fuel pressure gauge and turn the ignition on (do not start the engine).
• Check fuel pressure against manufacturer's specifications (typically around 50-60 psi for many models).
• If pressure is low, inspect the fuel pump and filter; replace them if necessary.

5. Inspect Oxygen Sensors

• Tools Required: O2 sensor socket
• Locate the upstream (pre-catalytic) oxygen sensor.
• Disconnect the sensor's wiring harness and remove it from the exhaust system.
• Inspect for damage or contamination; replace if necessary.
• If the sensor is functioning, test the signal using a multimeter.