Remove any dishes from the machine and pull out the racks to access the floor of the tub.
Unscrew the bolt at the top of the spray arm with a wrench. The spray arm is the piece that spins to disperse water. Once you take out the bolt, lift up on the arm to remove it.
Clean any debris out from under the arm and around the drain.
Take out the screws around the drain cover and lift it off. Wash the cover with hot, soapy water to clear out the holes.
Scoop out any debris under the cover and reassemble the dishwasher.
Run hot water into the sink drain and turn on the garbage disposal.
Pour 2 cups of white vinegar into a glass measuring cup. Place the cup on the bottom rack on run the dishwasher through one cycle with the it set to air-dry.