EVAP CODE P0455

Yes, that code which indicates evap gross (large)leak most common to be found that the gas cap was left off or not tightened.

If code cap is tight and you dont think you left it off, you may have to take to a shop that has a smoke machine to test the evap system, they will introduce smoke to system and visually look for evap leaks.

If no fault is found during the smoke test and the fuel gap was secured and is tested and checks ok, have the Engine Management Software updated. If the software is current then your problem will be a faulty leak detection pump.