The dishwasher fills with water, but isn't spraying water during the wash cycle, nor is it draining water during the drain cycle.

I removed the diffuser and both wash and drain impellers and none of these components were jammed. The pump shaft will also rotate during the wash and drain cycles with these parts removed. When I put the impellers back on the shaft, the shaft failed to turn.

I've checked the impedance of the motor run, wash start and drain start windings and all appear to be around 6-7 ohms.

I'm pretty sure that the motor is turning - if I cut power to the dishwasher while in the wash or drain cycle, you can hear the armature decelerating to a stop. Also, if I measure the voltage across the wash start and drain start windings, I read voltages of about 40 V, again indicating that the armature is turning.

I've also checked the motor start relay and seems to be OK as well.

Does anybody know if this motor has some sort of "transmission" between the armature and the pump shaft?

Thanks for the link. The service manual doesn't seem to address the issue I am having, though it does imply that the motor itself is not serviceable and must be replaced as a unit.

I should have mentioned that I can turn the pump shaft by hand quite freely with the impellers installed, but when the motor runs with the impellers installed, the pump shaft won't turn.

The next thing I plan to try is removing all of the pump components from the shaft and holding the shaft with my hand while I start the motor running. If I can prevent the shaft from turning with my hand and the shaft starts to turn when I let go, does that mean the motor needs to be replaced?