Dishwasher Whirlpool ADP905?

I have a Whirlpool Dishwasher Model ADP905. I have owned it for many years and purchased it when I was renovating a number of houses. In the past 2 months I have put it into use and its been fine until the other day. It has developed a fault. There are four green LED's on the left of the front ponel. The dishwasher starts up and I'm sure the first LED is for rinsing the dishes. Once this is completed it moves to the second LED which is the washing stage and the water is heated. However it will not move to the next stage and the second LED remains lit. The only way I can make it finish its cycle is to hold the Off/On button down.