P0455
P0455 EVAP Large Leak
P0455 means the EVAP system failed a leak check badly enough that the computer sees a large leak or no pressure/vacuum change.
How urgent is P0455?
It is usually not a drivability emergency, but fuel vapor leaks should not be ignored.
Common symptoms
- Check engine light
- Fuel smell
- Usually no performance issue
- Failed emissions readiness
Likely causes
- Loose/missing gas cap
- Broken EVAP hose
- Stuck-open purge valve
- Bad vent valve
- Cracked charcoal canister
What to check before replacing parts
1
Check gas cap first
2
Inspect visible EVAP hoses
3
Command purge and vent valves with a scan tool
4
Smoke-test system
5
Inspect canister and filler neck
Use the code with symptoms
A code points at the system, not always the failed part. Add your vehicle, mileage, symptoms, and whether the check engine light is steady or flashing so the AI diagnostic can narrow the next step.