my check engine light is on on 2006 Saturn Vue

I just purchase the vehicle less than a week ago. The engine light came on Monday and I took the vehicle back to the dealer on Monday. The vehicle was checked, stating they could not find a problem. The engine light has come on again.

Asked by for the 2006 Saturn Vue
Check the gas cap if worn it could cause this, If that is not the problem put a higher grade of gas. This happen to me and a friend told me to disconnect the battery and it will reset it selp (after you check the other) You have to trun it off and on a couple of times and then the light will go off. Mine has 63,000 miles and this happen to me.
1 more answer
I had the same problem. Ended up being a loose gas cap. Had to be replaced twice because the first one was defective. Suggest trying to replace the cap.