Dishwashers (AEG and Bosch) can do this for 2 reasons.
1. There is a leak ,and the bottom of the machine under the washing compartment is full of water which actuates a float switch to run the pump continuously.This is to prevent floods.
2. The pump impeller can get blocked-mine jammed on a pea-, which I think gave the same symptom. Remove the filter inside wash compartment and you can feel the pump impeller which should turn reasonably freely.You can test this by pouring water in the wash compartment, and see if it is pumped out of the outlet hose when the pump is running.
Richard
September 2008