Error 4 means that there is water underneath (usually from an "overfill") IF!! you dishwasher is out of warranty, underneath the door is a plate (as wide as the dishwasher) ind about 6inches high. Remove the screws and the kick board retainers, rear feet screws and prise off the plate, you should now see a float trip mechenisim, "!!!!switch off the dishwasher!!!!!" and using a sponge soak up the water, using something "Non conductive," trigger the switch a couple of times then restart the dishwasher."
The switch is triggered by a polystyrene float, water in the bottom will lift the float and trigger a drain cycle. Please also remember to check the sink hole in the inside of the dishwasher as food build up will adjust the water level, and send water down the overflow pipes. also note that water that has collected at the back of the dishwasher will move forward as the cycle vibrates the machine so may cause it again.
hope this helps all
Simon
Tobyhost.co.uk
tobyhost.co.uk, August 2007