I have a new (May 2009)Kenmore Elite Ultrawash Dishwasher that works 1 out of 4 times I use it. I keep getting an error code 8-1 and the soap is not all used up but the cup is open. I made Sears replace the electronics board, same problem. I made them replace the machine, same problem with a new machine. I have a loop in the drain hose that goes to the top of the cabinet just under the counter then connects to a separate trap under the floor off the main waste line. I have a well that was running between 20 and 50 psi. I adjusted the pressure switch on the well pump to cut in at 35 psi and cut out at 55 psi. This did not help. What could be wrong? I have been running the machine late at night so there is no other usage of water. I had a maytag that worked fine in the same location for 10 years and changed nothing about the installation when I installed this new machine.

Were you able to find a solution to this? I am experiencing the same thing, and it happens about half of the time. I've run it through the diagnostic sequence and it doesn't report and problems.

I did finally resolve the problem. It turns out that I did not have a vacuum break in the drain line. The drain hose was looped in the back of the dishwasher, then went through the floor and connected directly to a trap under the floor which then went to the main waste pipe. I had to rerout the hose to connect to the tail piece of my Kitchen sink. The drain needs to be open to the air or, as was happening to me, the closed piping will continue to siphon out the water in the tub of the machine after the drain cycle ends and cause the low water code in the troubleshooting guide. This was intermittent for me as well. The fix was a pain in the neck because I had to pull off the entire back of the cabinetry on my peninsula to get-r-done. Good luck with yours, please let me know how you make out, or if you need anymore help - just ask.

I have the same symrtoms:
8-1 code, intermittent 1 out of 10 uses, soap door open, no water in tub, soap still in tub, Technician has changed out control board, water control valve, door latch, & reconnected electric. My drain line connects to a separate drain that ties into the main drain. I'll try moving the drain to the disposal connection. My previous 2 dishwashers used the same drain without a problem for 20 years.