I tried sucking all the water out of the sump, removing the pump cover, checking that it spun…sucking out the drain line with wet/dry shop vac…dishwasher would run if we opened/closed the door after the first several seconds. Pulled it out from under the cabinet. Removed old pump, popped it open. It looked fine. Drain lines are clear. Check valve works fine. Everything looked good. Still getting this error code, and using the workaround of opening the door. Finally read a manual - I think Jeff posted it - saying that E24 error is probably not the pump and to reset the dishwasher. “P ress and hold “>” and Delay buttons, then turn dishwasher on. Left program light will flash and 2nd program light from left will be lit (on SHE5AM models, digital display will show “P0”). Press “<” button once to scroll to customer service test program. Left program light will be lit and digital display will show “P1”. Press “>” button to start program. Turn dishwasher off to exit program.” I let the program run through, which took a while, but ever since then the dishwasher has worked perfectly. I did purchase a new pump, and will keep it handy in case the problem returns.