Tommy, as you mentioned, what's most likely happened is, the Wire that runs from the Tow Haul Button, down the Shifter and then down the Steering Column and then down to the base of the Steering Column and overtime the Wire will get Pinched and/or Frayed, and then finally Break.......Here's a Picture of where the Wire is located, at the base of the Steering Column,04 Yukon, 185k. Pulled the boat out of winter storeage last weekend. Hit the trailer/tow button and nothing happened, no light, trans didn't shift, nothing. I pressed the button a few different times, nothing. Not sure if this is related, but I had the carrier bearings replaced in the front diff earlier this spring. Any relationship? I searched around here and didn't see much. Maybe a bad wire in the column? Anybody have any ideas?
There are two Very Small Gauge White wires inside the Orange sheathing..........to fix it, just stripped the wires back, twisted together and then soldered them back together and you should be good to go.