Tech Article Title Author Date
Do Not Fuel While Engine Started AudiWorld 1997

The A4 should never be fueled while the engine is started. If fuel is added while the car is running, the check engine light may come on. The car will have to be taken to the dealer for diagnostics and to have the Check Engine light reset.

This point of information is mentioned in the manual that comes with the car. It has actually happened to several people, including the author of this FAQ item!