My check engine light came on the other day and stayed on for a few engine start/stop cycles. I did the usual "take the gas cap off and put it back on" and that seemed to work... for a bit! But, it came back on and hasn't gone away for a few days. Are there any other quick fixes that I can try? I'd like to be able to figure this out w/o having to go to the shop. I only run premium fuel, its a 00 CLK320 with about 55K miles. Any thoughts???