Common Checks
- Inspect the cap or capless filler seal for dirt, damage, or poor closure.
- Check EVAP hoses if the cap/filler area passes inspection.
- Verify the code returns only after the EVAP monitor runs.
Diagnostic trouble code
P0457 EVAP System Leak Detected/Fuel Cap Loose
The PCM detects an EVAP leak pattern often associated with the fuel cap or filler seal.
EVAP Leak & Purge CodesCommon Repairs
- Tighten or replace the fuel cap where equipped.
- Clean the capless filler neck seal.
- Repair EVAP leaks found during smoke testing.
Mustang Notes
- This code should not be used as proof that the cap is the only possible fault.
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.