why does my Volkswagen Passat B8 (2015-2022) check engine light keep turning on?

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts during repairs.

2. Address Fault Codes

• Sub-step 1: Use an OBD-II scanner to read and document the fault codes.
• Sub-step 2: Research the codes to determine the associated problems (e.g., P0420 for catalyst efficiency).
• Sub-step 3: Clear the codes and observe if they return after a test drive.

3. Inspect and Replace Components

• Sub-step 1: For a faulty gas cap, replace it with a new OEM cap. Ensure it clicks securely when closed.
• Sub-step 2: If misfiring occurs, replace spark plugs and ignition coils as necessary. Use a torque wrench to tighten plugs to manufacturer specifications (typically around 20 Nm).
• Sub-step 3: If air intake leaks are found, replace or repair the affected hoses and gaskets.
• Sub-step 4: If fuel pressure is low, inspect the fuel pump and filter. Replace as needed following manufacturer instructions.

4. Test and Validate

• Sub-step 1: Reconnect the negative battery terminal.
• Sub-step 2: Start the engine and check for any abnormal sounds or behaviors.
• Sub-step 3: Conduct a test drive to ensure that the check engine light does not reappear.