My 2001 S500 check engine light came on today. It has 55000 miles and 3900 miles remaining until a schedule B maintainence. There was no noticeable difference in engine operation. Gas cap is tight. Can anybody give me an educated guess as to what could be causing this problem?

 

Can be any number of things. Looking at the mileage, i'd say an o2 sensor or most likely an air mass sensor. Both items are too expensive to guess though. Pull codes off of it, I think autozone should do it for free and the codes on this vehicle are pretty generic.