These trucks do not have a frame ground. All negative runs through wiring to battery negative. You really need a digital volt ohm meter to test this truck. You should not have any reading from truck wiring to frame. Your codes are for a open or short in the seat sensor wiring. check all the seat sensor wires for short to frame and to each other.

yes its an A/C system

this information is not of much value to me, as far as offering you troubleshooting help. can you confirm this truck is an A/C system? (3 power cables to the drive motor?)

with the test light connected on the working lift to power, it shows a complete circuit on any stud. the test light also had a digital screen telling me the voltage whether positive or ground side. and its a great connection. but on the non working lift the voltage is low but still strong enough to light up the two colored LEDs, and strong enough to switch. almost as if its searching for a frame ground

test light is not too good an idea,,, always use an ohm meter... you may be just seeing leakage from moisture on the top of the battery...

We took a test light from the postive cable at the controller on the Working lift to any bolt on the lift and had ground. The non working lift when doing the same changes the test light from power to ground a few times before the lift turns off. We removed the power and ground cables checking for anything that had shorted to the frame and both wires are clean

you say the -working- lift has a "frame ground"? do you mean a return to battery negative (shorted) through the frame? and the non working truck is clean to the frame on all power cables??

We have several times. All the way back to the master controller doing resistance tests and can't find any broken wires. When we compared to another lift exactly like it the only difference we can find is the lift that isn't working doesn't have frame ground but the working lift does

Hi Universal, check the seat sensor and wiring those codes refer to the seat sensor.

Regards Nero