A check engine light with hesitation and P0455 code in your 2018 GMC Canyon indicates the evaporative emission control system has detected a large leak. While EVAP issues primarily affect emissions, they can contribute to driveability symptoms when the purge system malfunctions.
Understanding P0455
P0455 indicates a significant leak in the EVAP system, which captures fuel vapors from the tank and routes them to the engine for burning. A large leak allows vapors to escape and can affect engine performance if the purge valve is involved.
Hesitation Connection
When the purge valve fails open, it creates a vacuum leak at the intake, affecting air-fuel mixture and causing hesitation. The purge valve normally opens in controlled amounts to introduce fuel vapors, but uncontrolled flow disrupts engine operation.
Common Leak Sources
A loose, damaged, or missing gas cap is the most frequent cause. Cracked filler neck allows vapor escape. Purge valve stuck open creates leak detection while also causing hesitation. Vent valve issues prevent proper system sealing. EVAP canister or hose damage allows vapor escape.
Gas Cap Priority
Always start with the gas cap—it's the simplest and most common cause. The cap should click firmly and seal without visible damage. Even a slightly warped or worn cap gasket fails to seal properly.