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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shock.
• Ensure the car is parked on a level surface and secure with wheel chocks.

2. Inspect and Replace Spark Plugs

• Remove the engine cover if applicable.
• Locate the spark plugs and remove the ignition coils by unscrewing them (tools: socket set).
• Extract the spark plugs using a spark plug socket and inspect for wear or carbon deposits.
• Replace old spark plugs with new ones, ensuring to torque them to the manufacturer’s specifications (usually around 22 lb-ft).
• Reinstall the ignition coils and engine cover.

3. Check and Replace Ignition Coils (if needed)

• If the spark plugs are fine, test ignition coils using a multimeter.
• Remove faulty ignition coils and replace them with new ones.
• Secure the coils properly and reconnect electrical connectors.

4. Inspect Fuel System

• Attach a fuel pressure gauge to the fuel rail and turn the ignition on (do not start the engine) to check for proper fuel pressure.
• If pressure is low, check the fuel pump and filter for issues; replace if necessary.

5. Check for Vacuum Leaks

• Visually inspect all vacuum hoses for cracks or disconnections.
• Use a smoke machine or carburetor cleaner to identify leaks by spraying around suspected areas.
• Replace any damaged hoses.

6. Clear Error Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the check engine light codes.
• Monitor the vehicle for any reoccurrence of the check engine light.