We purchased a JLG scan tool. Ran a system test. The truck failed Steer test. Also checked the Code log under "Help" it showed a Code 7740. Traction Current @ Zero. "Check shunt wiring". P2 on the power module checked fine. I could duplicate Code 77 by disconnecting P2 and powering up the truck. No Motor or wiring problems where found. I swapped Power controllers with another E600J and the code 77 cleared, so I installed the bad power module on the other lift and the code moved to that lift. Ordered new power module. Thank you for your direction.
Hope this helps others who may run into the same problem.