When your 2018 Chevrolet Traverse triggers a P0455 code after towing, the EVAP system has detected a large leak. While towing itself doesn't damage the EVAP system, the activities surrounding towing—refueling, vehicle motion, and heat—can trigger conditions that reveal existing issues or create new ones.
Understanding P0455
P0455 indicates a gross leak in the Evaporative Emission Control system—meaning a significant-sized hole or unsealed opening. The EVAP system captures fuel vapors from the tank and prevents them from entering the atmosphere. The system periodically tests itself for leaks; when a large leak is detected, P0455 sets.
Why Towing May Trigger the Code
Towing often involves refueling stops where the gas cap may not be properly sealed afterward. The EVAP system test runs when conditions are right, and towing trips provide those conditions. Heat from towing loads can stress vapor lines and connections. Trailer movement near the fuel fill area can sometimes disturb components. The code may have been developing and just happened to set during the trip.
Most Common Cause: Gas Cap
Over 50% of P0455 codes trace to the gas cap—either not tightened properly, cracked seal, or damaged threads. After towing involves highway driving and often refueling, this is the first item to check. Remove the cap, inspect the seal for cracks or debris, and reinstall with multiple clicks. Drive for a day or two and see if the code returns.
Other Causes
The charcoal canister can develop cracks. Vapor lines can become disconnected or cracked. The purge solenoid or vent solenoid may fail. The fuel tank itself or its sealing surfaces can develop issues. On the Traverse, check the EVAP connections near the fuel filler area and along the fuel tank.
Diagnostic and Repair
If the gas cap doesn't resolve the issue, a smoke test pinpoints the leak location by introducing visible smoke into the EVAP system under pressure. Costs vary: new gas cap ($15-$40), purge or vent solenoid ($150-$300), charcoal canister ($200-$400), vapor line repair ($100-$250). Smoke testing typically costs $75-$125 as a diagnostic service.