sat in my car at lunch with the a/c on. check engine light came on, turned off the car, tightened the gas cap, check engine light is still on. i think it takes awhile to reset; but if that's not the case, what do you guys think??

 

"check your engine" would be my guess.......

But then I'm not a mechanic......

However, I did stay at a Holiday Inn last night

 

Do you have a test pipe installed? If you have no cat then the check engine light will come on because it does not sense a cat.