On Tuesday evening of this week, my engine light came on in my van. The word 'gascap' has been popping on intermittently on my mileage display and so I thought that my gas cap was not on tight enough again. Although I have been pretty diligent to make sure that when ever I put gas in the car that I make sure the cap is on tight. So anyway, after the light didn't go away after I checked the gas cap and filled the gas tank, I checked the code. I am getting P0456. Twice. There is no P0456 in the code list. Any ideas??