Pete, I don't have a specific manual for this machine, however I am pretty sure that I have a wiring diagram in a GE Repair-Master for dishwashers. I'll have to get back to the other house to get to it, but I'll post if I can find anything useful.
There is a pressure switch in these impeller machines - to cut out the water valve to prevent too much water entering the tub and to run the pump if the water kept flowing in the event of an impeller motor failure.
I've got this exact model, too!