Whirlpool dishwashers are designed with a repair-friendly system. Their circuitry is universal and most parts can be removed without tools. Dishwashers are complex electrical appliances, though, that require extensive troubleshooting to diagnose the a problem.
Run a dishwasher cycle with nothing in the machine and watch for signs of your perceived issue.
Watch for the location of water leakage if this is your problem. Leakage from the front is a door seal issue. If water is dripping underneath, it is a pump seal issue. If water is flowing from the bottom and not stopping, it is a hose issue and the water should be immediately shut down.
Listen and watch for strange noises if it is a wash problem. If you don't hear anything, then it is most likely a detergent or water temperature issue. If you hear any clanking or do not hear water spraying, it is a clogged spray arm.
Observe your sink if it is a drainage problem. If the sink fills up with water, then it is the air gap. If there is no water in the sink, then it is most likely a clogged drain.
Remove and clean the door seal with a mixture of half hot white vinegar and half hot water with a sponge and set it firmly back into position.
Replace the pump seal by taking apart the pump all the way down to a small rubber seal shaped like a thimble. The pump comes apart easily in Whirlpool machines since only one bolt holds the entire pump together. Simply remove the bolt on top of the wash pump cover, and the rest of the pieces come off like a puzzle. Avoid confusion during reassembly by placing the pieces on the counter in order as you take the pieces off.
Replace the hoses by removing the four screws holding the kick plate in place. There will be two inside the machine and two underneath the door on the outside. Unscrew the hoses and screw on the replacements.
Use the right detergent. Whirlpool recommends using only Cascade because it dissolves properly in its dishwashers. It also recommends Jet Dry. Check the Jet Dry distributor regularly. Jet Dry softens the water and allows it to sheet instead of drip on the dishes. Sheeting refers to the way water disperses more evenly on the dishes.
Verify the water temperature by turning on the sink next to the dishwasher and putting your finger into the stream of hot water. The water should be so hot that you need to remove your finger from the stream. If not, the water is not hot enough for the dishwasher. Turn up your water heater to correct the temperature. Whirlpool recommends a water temperature of 65.6 degrees Cor optimal cleaning.
Remove the spray arm by unscrewing its bladder with your hand. The entire piece will come off. Shake the piece. If you hear something rattling inside, shake the spray arm upside down until the object falls out. If you cannot shake it out, replace the spray arm. Spray arms can be purchased at appliance repair stores or ordered directly from Whirlpool.
Locate the air gap under the sink between the sink's drainpipe and the dishwasher's drainpipe. It should have a white plastic cap.
Remove the cap and pour 1/2 cup of baking soda down each pipe using a funnel. Pour 1 cup of vinegar down the pipes and place the cap back into position. The foaming action will dissolve any build-up in the pipes.
Inspect the dishwasher's drain basket using a flashlight. Remove any debris inside the basket.
Pour 1 cup of baking soda inside the basket followed by 2 cups of vinegar, and let it bubble for 10 minutes. Rinse any residual baking soda down the drain. This will clear the basket and pipe of any unseen debris.
Most replacement parts will not be refundable; make sure that you are confident that the part requires replacement before purchasing the part.