P0457
Evaporative Emission System Leak Detected (Fuel Cap Loose/Off)
The EVAP system detected a large leak that strongly correlates with a missing or improperly closed fuel filler cap. After re-tightening the cap, the code clears once the readiness monitor completes.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: easy
Symptoms
- Check engine light on
- Possible smell of fuel near tank or engine bay
- Failed emissions inspection
- Loose-cap warning may appear
Common causes
Ordered by how often each turns out to be the cause.
- Fuel cap loose, missing, or worn sealCommon
- Filler neck damagedLess likely
Parts involved
- Fuel Filler Cap
- EVAP Lines
P0457 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.