what does code P0171 mean for my Volkswagen Passat B8 (2015-2022)?

Solution

1. Preparation

• Gather necessary tools and parts for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool if it has been running.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
  2. Use a smoke machine or carburetor cleaner to test for leaks around the intake manifold and gaskets.
  3. Replace any damaged hoses or gaskets identified during inspection.

3. Clean or Replace MAF Sensor

• Sub-steps:
  1. Locate the MAF sensor, usually found between the air filter and the throttle body.
  2. Disconnect the electrical connector from the MAF sensor.
  3. Carefully remove the MAF sensor from its housing.
  4. Clean the sensor wires with MAF cleaner spray; do not touch the wires with hands or tools.
  5. Reinstall the MAF sensor and reconnect the electrical connector.
  6. If the sensor is faulty, replace it with a new unit.

4. Test Fuel System

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail Schrader valve.
  2. Turn the ignition to the "ON" position (do not start) and check the fuel pressure reading against the manufacturer's specifications.
  3. If the pressure is low, inspect and replace the fuel pump or fuel filter as needed.

5. Inspect and Test Oxygen Sensors

• Sub-steps:
  1. Locate the upstream oxygen sensor in the exhaust system.
  2. Disconnect the electrical connector and remove the sensor using an oxygen sensor wrench.
  3. Test the sensor's resistance with a multimeter and compare it to specifications.
  4. Replace the sensor if it is out of specification.