What should I do to prepare my dishwasher for winter storage in an unheated location?

You should have a service technician cut off electric power to the dishwasher, turn off the water supply, disconnect the water inlet line from the water valve, and drain water from the inlet line and water valve. The technician should also remove the plastic pump cover in the tub bottom and use a sponge to soak up any water in the rubber boot. (Page 14)