My Whirlpool dishwasher is not draining during the wash cycle. It fills the bottom of the washer and eventually leaks out the door. The washer is about 1 1/2 yrs old and has worked fine to date. A couple other pieces of info:

1) There is no air gap.
2) The drain hose is connected to a disposal. The knock-out plug has been removed.
3) The disposal is not clogged.
4) I know the washer drain hose is not clogged. I can drain the water if I stop the wash cycle and then press "Start" by itself. The washer pumps the pooled water out of the bottom of the washer into the disposal with no problem.

It seems like something that is failing to work properly during the wash cycle.

Any thoughts on what to look for next would be greatly appreciated.

Jim