Hi JD, This code is communication error, software problem. can be expensive, or, simply bad connection. Orderpickers are very fussy about shorts to frame, static straps broken or the 10K resister that strap attaches to burns out. Use ohmeter from end of strap to frame, 10,000 ohms? You can change just the resister inside, Battery issues must be checked first,
Is there any voltage from post to frame? corrosion joining battery case to frame? You need to use amp meter on millivolts and connect to pos to frame, and and then neg to frame. Should not be any current. One millivolt can damage computer but i find you need 20 or more to really do damage. Sometimes find 250MV on truck that kept frying computers. Load test battery or use min/max on voltmeter while turning key on. Bad battery will drop for brief moment, like 17 volts on a 24 0r 25 volts from 36. Only meter with record can catch this. If that passes, leave bat unhooked and test for shorts to frame from pos and neg bat pins. Either one should have at least 200,000 ohms. If you see below that, like 150 ohms, then its a serious short. Unhook motors one at a time until short goes away. Shorts are sometimes on diode's, transisters, heat sinks.
These are standard tests fro all raymonds, but more important on OPC.
If all passed, then check connections inside panel. Without a manual, and direction, you can still check all plugs for corrosion and bent or backed out pins, wires broken inside from flexing. Go through some some re-start truck a few times to see if code cleared.
If you still have code, you need manual and deep pockets!