Many issues can plague a dishwasher and cause it to perform poorly or make it not work at all. If your machine is suddenly problematic, we advise that you schedule a service call with an experienced dishwasher repair technician. However, a few steps can be taken to attempt to diagnose the issue on your own end first.
What is wrong with your dishwasher?
Does it fail to fill up?
If so, make sure the water supply line wasn't inadvertently shut off. Be sure the fill hose isn't tangled: Check the water valve filter in case it clogged up from debris accumulation. With a multimeter, ensure the water inlet valve has proper continuity as well to verify it's opening when the fill cycle runs.
Does it fail to drain?
If so, make sure the drain hose isn't clogged. Take off the hose and attempt to blow through it to see if anything comes out. Make sure the drain and its filter isn't clogged as well. While the issue rarely lies here, inspect the disposer inlet to make sure it's properly connected. Lastly, run a continuity test with your multimeter on drain pump motor as this motor is responsible for activating the drain cycle.
Does it make loud or weird noises?
Most dishwashing machines are pretty loud in comparison to other kitchen appliances. However, excessive humming, squealing, buzzing, etc., is not normal. A worn-out bearing on the pump motor could cause a buzzing sound. While a grinding noise is usually normal, if it's excessive it is possible that a popcorn kernel or similar hard food item got stuck in a chopper blade. The drain pipe could also vibrate against the nearby cabinet and cause a thump-like noise.
Is your dishwasher shutting off on its own? If it's running intermittently, what could possibly be causing that to happen anyway? A safety shut off feature could be activating, likely due to an obstruction or kink in a hose. Often, this issue tends to lie within the drain hose or inlet pipe - check it to make sure this isn't to blame. The issue could be due to a failing part which causes the machine to malfunction - leave it to a dishwasher repair pro to diagnose if this is the case.