The first step to fix a blocked dishwasher is to make sure it finished its last cycle. Dishwashers don't drain completely until the cycle is complete, according to DoItYourself. The appliance tends to retain some water if something, such as a power failure, interrupts the cycle.
Check the fuse or circuit breaker that protects the dishwasher, and reset the breaker if necessary. Additionally, inspect the dishwasher door, and check to see if it has caused a malfunction. If the appliance is still blocked after performing these steps, the next solution is to clean the dishwasher, as large pieces of food may block its drain. Wear gloves, and remove any food from the bottom of the machine. The next time you put plates in the dishwasher, be sure to remove all leftover food to prevent blockage.
Examine the hoses running from the dishwasher to ensure they are still attached properly. Read the dishwasher manual to find out where the hoses are located and how to fix loose hoses. Check the hoses running from the dishwasher to the sink, and use a pipe snake or auger to remove blockages. Wire cut from a clothes hanger may also be used to unclog the pipes.