Wiring diagrams for LS XG 3135H and others are in this thread.

[Eagle1]

Great info; thanks! (Can you tell I've only been around tractors that are almost my age?)

Sounds like the cable will be an easy fix, and the regen is...only money. I'll see what the seller will do.

Big difference for me was the old BX will start and be ready to go and shut it down when ever.
The LS with it's Turbo and EPA stuff needs to run a bit before you take it out and needs a bit a bit of cool down below 1500 rpm if it worked at all.
The DPF and turbo like the tractor to be worked up to temp and not idled a lot or it will regen more than it should. I bought used as well and it not "right" until I did a parked regen and worked it harder (more rpm). Not wide open but do use above 2000 most of the time, PTO speed (2400) as needed not like the old iron that was happy just putting along just off idle.

Parked regen is brake set, neutral, rpm above 2000 then press and hold regen button for 10-20 seconds until it starts....then wait for it finish....15-30+ minutes.

If that runs but does not clear up the issue you may have a clogged DPF (clean or replace), a bad fuel injector in the DOC (can happen) or a problem with EGR valve. LS had the batch with that issues and there was an update (not all "dealer" read tech notes). Something about coolant getting into the turbo or other things. YMMV