On some dishwashers the pump impeller gets jammed up with small bits of debris. You can sometimes access it from inside the machine's washing chamber - right at the very bottom of the sump (best to remove water first) - a plastic cover with a single Torx screw.
Tweezers will help to get the bits out. The impeller should rotate with a bit of magnetic resistance.
Good luck...
Peccavi
March 2010
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