How to check a dishwasher's drain hose for blockage:

Common dishwasher drain hose Checking a drain hose
Disconnect the power source to your dishwasher before you conduct this or any other check. Either unplug the unit from the wall outlet, remove the appropriate fuse from the fuse box, or flip the appropriate breaker in the circuit breaker panel.

Before you can check your dishwasher's drain hose for a blockage, you have to gain access to the hose. First remove the lower kickplate panel located below the door. This panel can be removed by removing a couple of screws that are located either above or below the panel. On some models, the dishwasher door has to be open to access and remove the screws, but then closed in order to remove the panel.

With the panel removed, locate the drain hose. It is connected to the pump located below the lower spray arm. The drain hose runs from the pump to the sink drain, or to the air gap on top of the sink. There is a second hose leading from the pump that is a recirculation hose. When you are checking the drain hose for a blockage, you should check the recirculation hose as well.

Place a shallow pan below the hose to catch any spills. Disconnect the drain hose form the pump by pinching the wire clamp with pliers and then sliding the clamp up the hose. Remove the hose from the pump assembly and wiggle the hose in various locations. This may help to loosen the blocked debris.

Try running water through the hose to loosen and unblock the debris. A garden hose at full pressure is efficient to use for this task. Now disconnect the recirculation hose and check it for blockage in the same manner.

Once you have successfully removed any and all blockages from either or both hoses, reconnect each hose to the dishwasher. Replace the clamps, and replace the lower panel. Reconnect the dishwasher's power supply and run the dishwasher to make sure it is running proplerly.