About 3 weeks ago I didn't screw my gas cap on all the way and I got an error message, stopped the car, and screwed it back on. Then my check engine light came on the next time I started the car. I've heard this is pretty common. I had to take my car into the dealer because something was squeaking (totally unrelated of course) and they said it should go off in 4 or 5 days...it had already been a week at that point. Now it's been 3 weeks and it's still on. One of the tech's told me it was "one of those annoying government lights" and to not really worry about it since it would turn off. The manual says it could cause serious emmissions system damage if the car is driven with it on. Anybody know what this could be about? It's been 3 weeks.

 

Make sure you didn't turn the cap too far...the is a "sweet" spot. I had the same problem, I think it's not days, but the number of times you start the car (20 times maybe, I could be wrong here).

Check you cap, it should click into place, don't turn it all the way to the right (at least on my C280), were it "clicks" is the right spot.

 

Since the check engine light is almost definitely because of the gas cap, then it will not cause any damage to the emissions system. It is supposed to go out on its own, but if it doesn't, then take it to the dealer. They tell you to let it go out on its own because that is easier, but they can also turn it off with the computer.

 

Its not the number of times you start the car, its the number of times you start it up AND it has a chance to run through whatever the programmed OBDII "cycle" is, which includes a certain amount of driving. Just starting and stopping the car 10 times in your driveway won't do it.

I would take the car to the dealer at this point and have them read the code and clear the fault and the light.

 

I had the loose gas cap experince and the light never went off. The dealership told me it would, but off course, it did not.

Two months later I took it in and the dealer turned it off.