Plugged KitchenAid Dishwasher

Remove the spray arm by lifting it off.

Clean around the screen in the center, then lift that off to clean it better.

Some models have a snap out piece of plastic under the screen, remove and clean.

Check the operation of the drain valve. It may either be now working or plugged. I had a cherry pit plug mine. That has to be done from the underside of the machine. Remove the bottom front panel.

That last thing - the drain valve: On my Sears machine, it was clogged with just a little bit of some sort of vegetable stem that had turned into a little ball of fiber. The valve was white, and had a black rubber flapper inside. I removed just the drain hose and, assuming the flapper was part of the clog, ended up ruining it by sticking a hemostat through it. Don't make this same mistake. Remove the entire valve and check for clogs from the machine side, in really good light.