My check engine light start coming on in 2011. I have a toyola Corolla 2009. on 2009 Toyota Corolla

My check engine light start coming on in 2011. I have a toyola Corolla 2009. The light come s on within 30,60,and 90 days. Dealre have checked the problem. The only answer given is check your gas cap.Can some one tell me what is wrong with my car?

3 answers
what code does it come out with and have bought a new gas to see if its the problem.
you need a new shop. you have an evap issue and it is difficult to diag but can be done by a competent shop.

Roy
It's awful if the dealer can't fix an evap problem, canisters fail a bit but as Roy said any competent shop can do it by using a "smoke machine" to check for leaks.