Best we have ever been able to figure out here is that they do not exist, except maybe in the hands of the techs wiring the units. And then probably schematics rather than wiring diagrams. And schematics do not help a whole lot if you are trying to figure out exactly how something is wired.
When we bought our trailer new, we had a wiring problem in the living room. Took the techs a while to figure out that our living room outlets and refrigerator was wired to our ceiling fan switch. Fan on/refrigerator and outlets worked. Fan off/refrigerator and outlets did not work.
I asked the service manager if he could get me a copy of the wiring diagrams. He contacted Keystone and they said they could not supply wiring diagrams even to the service manager. Go figure.