kenmore 66513469 not draining 90% of the time

[tbrown10]

I have a Kenmore dishwasher that won't drain most of the time.  I have done the standard steps of cleaning the drain area inside the dishwasher and snaking the drain hose and still nothing. Next I disconnected the drain hose from the dishwasher and after cleaning up the water from the kitchen floor I put the hose back on and the dishwasher started draining again.  After like two tests it stopped draining again but the pump is running.  I then replaced the drain hose thinking the the small check valve in the hose might be sticking.  After testing it's the same story works once or twice then stops draining.  Any ideas? It's a kenmore 66513469

[Vance R]

First it you have one is to check the airgap at back of the counter near the sink. Pull off silver trim cap and then remove plastic cap. Make sure it is clean and clear. 
Next would be to remove drain pump and check impeller cavity and impeller. Make sure to have towel on hand for the water. You can reduce the amount of water with vacuuming out sump with wet dry vacuum.