Intermittently, my dishwasher will fill, but the wash cycle won't start. I checked the power to the circulation motor and it was zero. After a period, sometimes assisted by opening and closing the door, the motor will start. My meter, of course, now indicated power to the motor. The dishwasher start light remains on, even when power was not available at the motor, and power had to be available to the water valve in order to fill the machine. In addition, sometimes the wash cycle won't restart when interrupted to add a dish. I concluded, apparently erroneously, that the electronic control unit was bad and replaced same. After a week or two of correct operation, the erratic wash operation started again. I thought that the replacement control unit was bad and exchanged it for another. However, the same erratic wash behavior started again with the second replaced control unit.

The circulation pump as well as the water valve, drain pump, and vent motor seem to work OK in Service Mode.

Is there a feedback or response that indicates to the electronic control unit that the dishwasher is now full and the wash cycle should start? If so, I can't find it on the wiring diagram. The only thing that the control unit appears to monitor is the turbidity/temperature sensor Could a malfunctioning the turbidity/temperature sensor affect the wash start?

Does anybody have any suggestions as to what the dishwasher problem might be? I am stumped. The dishwasher is in good condition, therefore I would prefer to fix it rather than replace it.