Hi there,
I have two Mercedes (E430, 1999 and ML320, 1998) and it seem like both having the same problem. When the gas tank is almost empty or close to empty the check engine light goes on, and after getting gas and driving for a bit it will go away. Sometimes, it happens when the gas level is just passed the half full. Also yesterday, when I parked on steep driveway with head down the light was off; however, when I started the car the check engine light was back on and because of steep the level of gas was close to empty. Any idea what is wrong?