What should I do if there is standing water at the bottom of the dishwasher tub?

A small amount of water around the outlet on the tub bottom at the back is normal — it is clean water that keeps the water seal lubricated. If the entire bottom of the tub has water, you may have a drain problem; check and clean the air gap if you have one, check that the kitchen sink is draining properly, and if the dishwasher drains into a disposer, run the disposer to clear any clog. (Page 13)