It's long time since I've seen this question come up, and the info has slowly seeped back into this brain of mine.
First you will need a sappy hand held analizer unit. First all those fault codes you see in the canbus need deleting then start and use the truck
The first code that reappears is where the problem lies, if it points to canbus error then change the canbus, if it says joystick problem then check out the joystick, this joystick has a lot todo reach in and out hoist and lower also the horn is incorporated. The unit is made up with lots of micro mini switches. Anything that small is prone to wear and breakage, the wiring on these trucks is quite reliable I can't ever remember having to repair wiring on these trucks and normally they are quite reliable. If you don't have a zappy diagnostic had held unit, then you may have to get a Yale tech in with his laptop to delete codes.