DIAGNOSIS A non-draining LG dishwasher is almost always a clog in the drain system. The most common culprit is food debris stuck in the filter assembly or the drain hose.
FIX Start by removing the bottom rack and unscrewing the cylindrical filter in the center of the tub floor. Pull it apart—there's a coarse filter and a fine filter. Rinse all pieces under hot water, scrubbing away any sludge. Check the exposed drain area for large debris. Reassemble tightly.
IF THAT DIDN'T WORK The next spot to check is where the drain hose connects to the garbage disposal or sink drain under the sink. Disconnect it (have a towel ready) and check for a kink or blockage. Also, if you have an air gap device for your sink, it might be clogged.
HEADS UP Never run a cycle with the filter removed or loosely assembled. It protects the pump from damage, and a bad seal can cause leaks. And yeah, you gotta clean that filter way more often than you think.