ACA9202 diplomat dishwasher not cle...

Hi there, we have an intergrated diplomat dishwasher, normally when its finished its wash it bleeps 3 times and then you know its finished, but recently it bleeps mid wash and the light that is normally on the end wash cycle automatically puts itself to the first cycle and the dishes etc aren'tclean. i have cleaned it out, checked the inside out and everything seems fine. can you help? otherwise its gonna cost a fortune to get fixed.
thanks

debs