After fighting for a day more than I wanted and spending $ on two mechanics and still no closer, I have walked away.
They did not have any problems giving my money back.
14 hour drive each way and two days on this thing is rough to leave with nothing.
My RE bus has a red emergency stop mushroom button in the back that is also the lockout. With mine you have to turn it and let it pop out. I have also a small 15 amp fuse close and directly connected to the battery that holds the computers alive.
My wiring in the back has writing on it. Did you find the ECM and see if any identifying writing is on the wires?