When your dishwasher cleans your dishes, some of the cycles are timed to run for a specific amount of time, but your dishwasher also uses a turbidity sensor primarily when rinsing those dishes. The turbidity sensor only has one job and that is to sense how clean the water is. The turbidity sensor is charged with detecting particles in the water during the rinse. When the water runs clear, it stops the cycle and begins the dry cycle.
When a turbidity sensor is possibly malfunctioning, the problem you will have on your hands is that your dishwasher runs forever. That wash cycle that should be done in an hour is still running five hours later. However, there could be other problems at play.
A sign that your dishwasher turbidity sensor is responsible for your infinitely running dishwasher is that it will actually drain when you hit the cancel button. If the problem were, for example, that your dishes weren’t drying and water was left inside, it could mean that your drain pump or hose are clogged. However, if it drains when you manually tell it to, and the water looks clear, it is likely the turbidity sensor is malfunctioning. The part is reading particles in the water and as such running the rinse cycle indefinitely.
This part is located behind the drain pump on your dishwasher near the back. Unfortunately, you will need to uninstall your dishwasher and lay it on its back so that you can access this part. Luckily, that is most of the work for this replacement. Once you have access to the bottom of your dishwasher all you need to do is unplug the old turbidity sensor and install a new one. The uninstalling and reinstalling of your built-in dishwasher is really the most complex part of this repair. However, once replaced, your dishwasher should run as designed again.