I finally took mine into the dealer today after the check engine light kept coming on at least once per tank of gas. It would remain lit until after I had refueled, usually after the 2nd or 3rd errand after the gas station. I was very conscious about tightening down the gas cap every time, so it was not the "didn't tighten properly" problem.

Turns out that I need a new catalytic converter. I have only 25000 miles on this '05 HAH. Good thing it's under warranty!