what causes the check engine light to stay on in Volkswagen Passat B8 (2015-2022)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the ignition is off.
• Disconnect the battery to prevent electrical shorts.

2. Address Fault Codes

• Sub-steps:
  • Use the OBD-II scanner to read and note all stored error codes.
  • Research and diagnose based on the specific codes retrieved (e.g., P0420 for catalytic converter efficiency).

3. Inspect and Replace Components

• Sub-steps:
  • If spark plugs are faulty, remove the ignition coils, take out the old spark plugs, and install new ones using a torque wrench set to the manufacturer’s specifications (usually around 15-20 Nm).
  • If the gas cap is damaged, replace it with a new OEM gas cap.

4. Repair Vacuum Leaks

• Sub-steps:
  • Inspect all vacuum hoses for cracks or disconnections.
  • Replace damaged hoses and ensure all connections are secure.

5. Fuel System Check

• Sub-steps:
  • Use a fuel pressure gauge to check for proper fuel pressure (should be within the manufacturer's specified range).
  • Replace the fuel filter if it is clogged or has not been serviced according to the maintenance schedule.