Common Checks
- Verify the fuel cap is present and sealing, or inspect the capless filler door and seal.
- Inspect EVAP hoses near the tank, canister, and purge valve.
- Use a smoke test to locate large leaks.
Diagnostic trouble code
P0455 EVAP System Gross Leak Detected
The EVAP monitor detects a large vapor leak.
EVAP Leak & Purge CodesCommon Repairs
- Replace a missing or failed fuel cap where equipped.
- Repair damaged vapor lines or disconnected EVAP hoses.
- Replace a purge or vent valve stuck open after confirming the fault.
Mustang Notes
- On later capless cars, debris at the filler seal can trigger leak codes.
Model-Year Applicability
Listed for 1996 and newer traditional gasoline Mustang pages in this first-pass catalog. Engine, calibration, and Ford-specific codes may narrow that range as more service data is added.