My CEL goes on for about 2 days, then goes off for 2-3 days, then maybe a day or 2 later it goes on again, etc. This keeps repeating. There doesn't seem to be any obvious reason when the light goes on or off. When it first happened, I drove to the dealer but the CEL light went off after I got there so I drove away without them checking. I've been driving like this for the last 3000 miles... Does CEL indicate a problem only when it's lit continuously? I will be taking my 6 to the dealer for inspection soon (have 21000 mi on it), but what if the CEL is not lit when I take it to the dealer? Will they still be able to diagnose the problem? Does anyone else have this kind of problem?