Hi,
My 4 year old Kenmore Ultrawash dishwasher has stopped draining at the end
of the wash cycle. I checked for blockages and its OK. If I hit the
'Cancel/Drain' button it immediately pumps the water out, unless we have it
set for heated dry, then it needs to sit for a while (I'm guessing to let
things cool down) before the cancel/drain button will work.

Any idea what the problem could be? How do I troubleshoot this to be sure?

Thanks,
Jon

Since it seems that it is draining fine at other times during the
cycle, and when you manually command it, then it sounds like the
controler/timer.