If your truck is difficult to fill at the gas station and your check engine light is on, you could have a failed EVAP Canister Vent Solenoid. Over time, water and dust can cause the valve to seize, which can either make the ECU think the gas cap is loose or when filling up, the gas pump continuously shuts off before the tank is full. This will cause the check engine light to illuminate with the diagnostic trouble codes of P0449 and P0455.