check engine light and gas cap?

Mita, the dealership told you that the gas cap is not sealing properly, why don't you just order that cap?

I cant say for sure but the gas cap is a common problem

go to auto zone and have codes scanned for free and post so we can adv

Looks can be deceiving , especially when the valving in a gas cap is not easily visible. The round o-ring you see is often not the part that leaks. IF they are set-up for emissions testing , then they should have equipment to test and verify gas cap failure........Maybe not enough fiber in cars diet??