Locate and gain access to your dishwasher's belt. It will be located behind the lower kickplate panel. The belt will be made of rubber and will be about twenty-five inches long. Some are clear in color, while others are black. The belt will be looped around a pulley at the base of the pump assembly and around a pulley at the base of the motor. The motor will likely be towards the right, with the pump assembly located closer to the middle.
You do not have to move the dishwasher away from the wall in order to access and/or replace its belt. You only need to remove the lower kickplate/access panel. There will be a few screws holding the lower access panel in place. Remove these screws to remove the panel. You may need to first open the door to remove the screws, but then close the door to remove the panel.
With the lower panel removed, the belt is fully exposed. Closely examine your dishwasher's belt. You are looking for signs of wear such as little cracks in the rubber and places where the belt may be stretched. If you find signs that your belt is worn, replace it.