how to diagnose P0455 code on a Volkswagen Passat B8 (2015-2022)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety during repairs.
• Raise the vehicle using a jack and secure with jack stands if accessing undercarriage components.

2. Inspect and Replace Fuel Filler Cap

• Remove the fuel filler cap and inspect its seal for damage.
• If damaged, replace with a new fuel filler cap. Ensure it is the correct part for the Passat B8.
• Reinstall the cap and ensure it clicks into place securely.

3. Repair EVAP Hoses

• Locate all EVAP hoses connected to the charcoal canister and purge valve.
• Inspect hoses for cracks or disconnections. Replace any damaged hoses with OEM parts.
• Reattach all hoses securely.

4. Smoke Test Procedure

• Connect a smoke machine to the EVAP system at the fuel filler neck.
• Activate the smoke machine and observe for smoke leaks from any EVAP components.
• Identify and repair any leaks found, replacing faulty components as necessary.

5. Test EVAP Purge Valve and Vent Valve

• Disconnect the electrical connectors from the EVAP purge valve and vent valve.
• Using a multimeter, measure the resistance; compare results with the manufacturer specifications.
• If either valve is faulty, replace with an OEM part.

6. Clear Codes and Test Drive

• Reconnect the battery and use an OBD-II scanner to clear the P0455 code.
• Test drive the vehicle to ensure the check engine light does not reappear and monitor engine performance.