E4 means that the sump below the dishwasher has filled with water. It doesn't take much for the polystyrene float to trip a switch, which in turn runs the pump to empty the d/w and beeps. The water was leaking from the overflow pipe which wasn't sealed properly into the d/w, the pipes are located at the front bottom of the d/w. Hope this helps.
Darren., May 2006