OBD-II CODE / EVAP
P0455 · Large evaporative emissions system leak
The EVAP monitor detected a large leak or a failure to seal during its test of the fuel vapor system.
Part of the EVAP system guide.
What the EVAP system tests
The system contains fuel vapors and routes them to the engine when commanded. The monitor checks the system under particular conditions, so the light may come on after the event that caused the leak.
Start with the filler area
Note whether the light followed a fill-up. If the filler seal looks sound and the code returns, follow the vehicle’s leak-test procedure for the lines, valves and other components. Use equipment rated for EVAP testing.
A vehicle-specific example
Nissan’s bulletin gives a defined flowchart for covered vehicles with P0455, P0442 or P0456, and treats the filler-cap check as the start of the process.