On the 2001 E320, I have been experiencing an intermittent check engine condition. The car experiences no symptoms when the light is illuminated. Today, however, I fueled up at Exxon (I always top off 2 times after the lever clicks), and I noticed that the fuel gauge did not go all the way to full (1/1) when the car was started. Does this mean I have an air pocket in the fuel tank (triggering the check engine light)?