Diplomat ADP8322 problem

i have a dishwasher ADP8322, the fault bleep is sounding and the programme light for pre-rinse is lit,after it had been on a normal wash, the pump is running and there is no water in ths bottom of the dishwasher under the plastic flap. i have tested the outlet hose and there is no blockage or leaks, the inlet hose is also free from blockages. anybody have any ideas what the problem is.