I have been tracking messages on the check engine light and P0455 for nearly two years. Vacuum lines, charcoal canisters, purge valves, fuel tank feed and return line fittings, check valves and such--no go! This is my wife's car, I put gas in it for the first time in years yesterday. As the tank topped up, the car spilled fuel from above the tank. Though I had checked this several times before, I finally found that that fill pipe overflow return hose to the main tank was split near the fuel pump, but on its underside. Only the fuel trail pointed to the spot. The crack was not visible via the fuel pump access cover. Best access is by removing the sender cover and screw on collar as well, though I did not have to remove the fuel pump retainer collar. No light at last! Certainly not the only answer, but one of many.