Over the last couple of months I've gotten code PO456 and a gascap warning on the dash a couple of times so I replaced the gas cap a week ago. About a 1/2 mile from the house gascap came across the dash. I pulled over and double checked to make sure the cap was tight. The gascap message disappears on it's own after several miles. The code needed to be cleared. No codes since I replaced the cap.

Any thoughts?