Gm auto track transfer case question

[Striper80]

I know Ferm is pretty knowledgeable when it comes to gm, among other things, so I figured I'd post here. I have an 05 Sierra 1500 non HD with an auto track transfer case. I've owned the truck since new and had very few problems over the years. Last year I started getting a service 4wd message once in a while that would clear out after cycling the ignition. After a little while the truck got stuck in 4 wheel. I tested the switch and thought I had a bad one but apparently I just screwed up testing it, because it was fine. I asked the mechanic next to my shop if he could check the codes for me so I could look into it further. He checked them, said he wanted to check it a little further for like $100 so I said sure. I didn't want to throw parts at it so I obliged. Well one thing led to another and I wound up spending a lot of money on parts that in the end I could've just bought and swapped myself.
In the end I thought it was fixed but with today's snow I noticed I have no 4wd. The lights on the dash change and auto 4wd works but 4lo and 4hi have nothing. Anyone here have a clue?