P0455 Evaporative Emission Control System Leak Detected (Large Leak / No Flow)
The EVAP system detected a large leak (approximately 0.080" or larger) or no flow during the leak test.
Definition
P0455 is essentially P0442 escalated. Causes overlap heavily (gas cap, hoses, solenoids), but the leak is larger and easier to find — often a disconnected hose or completely missing gas cap.
Common causes
- Missing or grossly loose gas cap
- Disconnected or torn EVAP hose
- Stuck-open purge or vent solenoid
- Severely damaged charcoal canister
Common misdiagnoses
- Replacing the gas cap when an obvious hose is disconnected.
Troubleshooting steps
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1. Verify the gas cap is present and tight
Listen for the ratcheting clicks (where applicable).
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2. Smoke-test the EVAP system
Larger leaks are easier to find with a smoke machine than small leaks.
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3. Inspect EVAP solenoids and hoses
Trace the EVAP plumbing from the tank to the canister to the intake.