OBD codes / P0455 / Honda Civic
P0455 on a Honda Civic
Evaporative Emission System Leak Detected (Large Leak)
All modern Civics with the sealed EVAP system.
What P0455 usually means on a Civic
P0455 flags a large leak in the Civic's evaporative-emissions system, meaning fuel vapor is escaping rather than being captured. The overwhelmingly common cause is a loose, cracked, or worn gas cap seal. Beyond that, Honda's canister vent valve and the EVAP hoses are the usual suspects. It never affects driveability but will fail an emissions test.
Most likely causes on this model
- Loose or failed gas cap
A cap that no longer seals is the number-one P0455 cause across all Civics; check it first.
- Canister vent valve stuck open
Honda vent valves stick, especially where road salt is used, leaving the system unable to seal.
- Cracked EVAP hose or line
Aged rubber lines near the tank and canister split and leak large volumes of vapor.
- Failed EVAP canister
A cracked charcoal canister leaks and can also clog, setting large-leak faults.
What it costs on a Civic
A gas cap is a fifteen-to-thirty-dollar fix and clears many P0455s after a few drive cycles. A canister vent valve is a moderate part and easy to reach on most Civics. Only a full canister replacement pushes the job toward the higher end, and even that is well under a major repair.
Civic owners also ask
Can I just tighten the gas cap to clear P0455 on my Civic?
If the cap was loose, retightening it and driving several cycles often clears the code; if it returns, the cap seal or vent valve is likely at fault.
Does P0455 mean my Civic is leaking fuel?
No liquid fuel is leaking - the code is about escaping fuel vapor from the EVAP system, most often a gas cap or vent valve, so it is an emissions issue rather than a safety leak.
Year, engine and mileage change the answer. Get a diagnosis for your Civic — it weighs these causes against your exact configuration and real complaint data.
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Based on widely reported patterns for this model; individual causes vary by year, engine and history. Generic P0455 behavior is covered on the main P0455 page. Confirm with a scan tool before buying parts.