It's cheaper to have someone scan it than to go buy a scanner that can communicate with that system.
Most generic scanners can get engine and trans trouble codes that are setting currently. Some don't even display codes that are set in history even though they are in the computer.
As far as the cold temp, I was talking more like -10 F or so. We had a lot of vehicles stuck in 4 lo this last winter. By the time they came into the shop and got thawed out, everything started working again.
I do know that if you look in your history repairs from the dealer, they should have documented which code or codes were setting. Maybe that will give us a clue.
I would think they should at least scan the computer for you. If you wind up with something like a C0327 and they replaced the encoder motor sensor but failed to reprogram the TCCM then the new sensor may have failed again. The factory has several updates for TCCM calibration errors so they need to be updated if they weren't.
There are also documents from the factory that talk about delays or hard time coming out of 4 hi or 4 lo if you have badly worn or mismatched tires. The tire size mismatch causes severe binding in the transfercase and won't allow the gears and clutches to uncouple. Make sure your tires are matched closely as far as their total circumference.
If you have new tires on the back and worn tires on the front and it goes intoXXXXX then the different size tires spin at different speeds which is where the binding occurs.
Let me know if you find any documentation. Maybe try hooking things back up again and give it a try.