E4 Check the pressure switch - a round item about 3 inches across with several wires connected, it sits under the top cover. Its an air operated switch which tells the machine water has reached the correct level. Disconnect the thin rubber pipe from the switch and blow down through it to clear any blockage. Switch itself may be faulty but its more likely the pipe is blocked.
Also check the filter - generally located behind a panel at the foot of the machine.Some are obvious like little square hatches and some are hidden behind the trim panel at the foot of the machine. Once panel is removed the filter will be seen. Its a circular fitting which generally unscrews in an anticlockwise direction.
Some filters are pretty well disguised by the manufacturers which is a big help to their customers and some machines have no filters at all which allows all manner of debris and detritus directly into the pump.
Check out my site for info: www.2ndwave.co.uk/manual.html
dan
February 2008