I have looked through both designs of 4wd, AWD and electronic 4wd. The only black wire in the entire schematic is a ground. It does not come from the wiring at the transfer case, but rather the switch. In both cases, it is a ground that is between the switch and the left front foot-well. The first picture is a portion of the schematic for the electronic 4wd. The second pic is from the AWD system. Are you certain it is a black wire? Let me know if this helps or if you have other questions.
Check out the diagrams (Below). Please let us know what happens.
Images (Click to enlarge)
Monday, April 12th, 2021 AT 12:15 PM