Hmmm... air leaks? vaccum leaks? let me check those... but could there be anything that will leak in the fuel tank? like sensor or stuff like that?

This afternoon when I was driving the car, it was about 78 degrees and the tank is about 3/4 full... the message came on after about 15 minutes of drive...

I reset the OBDII code, and tonight about 65 degrees, the message hasn't popped up at all during about an hour of drive.

Could temperature have something to do with it? Or could it be something else? How do I check for vaccum leaks on a W220? Anyone has a vaccum diagram?

Please help! Thanks!