Been doing a little more diagnosing when I'm able. Wasn't feeling too good the past few days, but I was able to get out to the garage for a little bit. I tested pins F13 and F14 of the tccm connector to verify that there was voltage on the reference wires, and there was. I then pulled the selector switch and the encoder logic connector, and found that they are both getting the proper 8v. None of the wires in the 4 pin connector at the encoder motor show continuity to the case, and the resistance between the red and black shift motor wires are within spec. I seemed to remember that 3 of the pins on the 6 pin encoder logic connector had continuity to to the case, but I rechecked and only pin F showed continuity. Pin F is the Channel P wire. Not sure if that's normal.

There's a couple people I found parting out a number of vehicles, and they each have Blazers, Silverados, ect. Going to try to make it to one of them with a battery to test a few to find one that works properly, and grab both the tccm and encoder motor.