If the dishwasher is hooked into a garburetor, there is a plug in the garburetor where the hose drain attaches that needs to be knocked out. The drain hose might be plugged where it joins to the plumbing drainage. The other problem, plumbing-wise, is the drain hose has to be fed as high as it can go under the sink and back down into the drain.
Shut the electrical breaker off and lock it out. Undo the drain hose under your sink. Shut off the water supply under the sink to your dishwasher.Take the bottom front panel off the dishwasher. Undo the water supply attachment to your dishwasher. Open the door to your dishwasher and take out the screws attaching the dishwasher to the counter. Undo the electrical connection to the dishwasher. Slide the dishwasher out. You may have to adjust the legs to get the dishwasher out. If you have a new dishwasher to install, read the directions for installing it, do the reverse to take the old one out.
Probably the drain hose from the dishwasher isn't high enough to keep the water from running back . The hose should be above the level of the disposal at some point. Some states require an "air gap" which is a device that is placed in the drain line to prevent this. Some states require a simple high loop in the drain hose. Many dishwasher manufacturers are now installing backflow preventers in the dishwasher.
The sink drain is plugged,or you have the dishwasher hose hooked up in wrong place.
It is not recommended to use drain cleaner in a dishwasher as it can damage the dishwasher components and create a safety hazard. Instead, consider using dishwasher-specific cleaner or vinegar to clean your dishwasher.
The height of the drain really doesn't matter as long as the hose from the dishwasher has a section that is at least half as high as the dishwasher.
If if won't pump all water out, the d/w hose or sink drain is plugged.
You would have to put a casing around it, find a different incoming water hose, and adapt the drain hose.
A faulty pump, a faulty switch, a faulty release valve on the drain pipe.
The rubber hose leading from your airgap to your garbage disposal or drain pipe is propably plugged. Remove hose and clean or replace. Also, when you remove the hose leading from the airgap to the garbage disposal, check to ensure that your stopper plug is removed from the garbage disposal. The stopper plug is a metal or rubber plug placed in the garbage disposal for people that don't have a dishwasher. The best way to remove this plug is by taking a screwdriver and placing it on the plug and gently tapping the butt of the screwdriver with a hammer until the plug pops out. Use metal fingers to remove the plug from the upper hopper chamber of the garbage disposal or (if you are daring enough) remove with your hands.
Remove the bottom hose to drain the system. Remove the top one as well and flush from the top with a brisk flow from a hose pipe.
Remove the oil pan drain plug to drain the oil. Remove the lower radiator hose to drain the coolant.