are you absolutely sure about the switches?
they are/were usually mounted on the linkage bars down near the control valve spools on the link bars themselves.
If they did do away with the standard micro switches they may have replaced them with holographic magnetic switches, or the switches may be mounted on the bottom side of the spool assy's where you cannot see them unless you pull the floor plate and look under the valve assy. There has to be some type of switch there to activate the hydraulic pump when the lever is pulled.
I do not have a VG series truck manual but i do have a GH series which isn't too far behind that one and it shows the same setup that yale has used for years with the switches on the link bars connecting to the control valve spools.

As far as that overheating code yes, check the temperature sensor on the motor and make sure its not shorted or any of it's wiring not damaged. Providing that code is related to the motor and not the controller, if there is no heat sensor on the motor then it's probably a controller overheat code, then you may wind up having to replace the controller since the sensor is inside it's case on the heatsink.