If you've ever noticed your dishwasher making a humming noise but not running water, don't worry. One possibility is that the dishwasher is in "idle" mode. In this mode, the dishwasher waits for the water to heat up to the correct temperature before beginning the washing cycle.  It can take a minute or two, so give it time if you immediately notice your dishwasher humming but not running water. The water should eventually kick on and start filling up the tub.