P0455
Evaporative Emission System Leak Detected (Large Leak)
A large leak has been detected during the EVAP system pressure or vacuum test — large enough that the system cannot hold pressure for the diagnostic interval. Typically a missing fuel cap, disconnected hose, or split canister.
- 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 missing or not seatedCommon
- EVAP hose disconnectedCommon
- Charcoal canister crackedPossible
Parts involved
- Fuel Filler Cap
- EVAP Canister
- EVAP Hose
P0455 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.