Disconnect power to the dishwasher by turning off the breaker in your fuse box.
Open the door of the dishwasher, then remove the lower rack. The lower rack can simply be lifted out of the dishwasher.
Lift the tab on the water-supply tub on the back of the bottom assembly, then rotate the assembly clockwise to release the wash arm on the bottom of the dishwasher. Remove the lower wash arm.
Remove the screws located in the area that was covered by the lower wash arm, consisting of the lower wash-arm support and water-filter assembly.
Pull the assembly straight out of the dishwasher.
Remove the screws securing the foreign-object protector, located at the front of the drain assembly, then pull the foreign-object protector out of the dishwasher.
Remove the screw on the round pump-inlet protector, located to the left of the foreign-object protector. Remove the pump-inlet protector.
Locate the check valve, located on the right side of the area covered by the pump-inlet protector. Remove the check valve using needle-nose pliers.
Insert the new check valve using the needle-nose pliers, then replace the pump-inlet and foreign-object protectors, securing both with the screws that were originally removed.
Replace the lower wash-arm support and filter assembly, then secure using the screws that were originally removed.
Place the lower wash-arm assembly into place, then rotate counterclockwise to secure.
Reconnect the tub on the back of the wash arm with the water-supply tube, ensuring that they snap into place.
Place the lower rack back into the dishwasher, then close the door and restore power to the appliance to complete the replacement of the check valve.