two ways .1 call and engineer or 2.
take off the bottom plate. Youll see that this has a switch on it to which makes sure the machine cant operate when this switch isnt made.
Now follow the drain hose (grey) to a small pump.
This is located in the front righthand corner of the dishwasher unit.
Its held in by 3 screws and has an o' seal. remove these and pull the pump out.clean off the gunge to make sure the plunge switch is moving freely.And reassemble...Do make sure that the seal is made properly when refitting the pump otherwise when you switch on after about a minute you will have water on your floor.
roy
December 2006