Took the drain pump off and cleared the lines going to and from the pump. Cleared and cleaned the air gap at the top of the sink. On the Samsung DMT300RFS the drain pump twists off. The pump has four tabs that lock it on to the pump body. The tabs fit into tapered slots. The tabs can become brittle from heat over time and will not seat the pump upon replacing. I ordered a new pump that came with a new O ring. I also cleand the fill float chamber on the left side of the unit. The dishwasher works like its new! I also cleaned the drain pan on the inside of the machine. Remove all the screws and take the drain filer screen off and clean underneath. I fill like I saved myself $600.oo dollars.