First - TC is transfer case.
Second - You're looking at the diagram - whether it's the one from the link than IanL provided or the one from the "digital copy" on your PC - they both show the same thing - that the 4WD switch, when in the 4WD position switches the black/orange wire to ground, so grounding the black/orange wire activates the front differential freewheel clutch.
To activate 4WD you need to activate the front differential AND shift the transfer case.
Third - USD$90 is cheap for a hardcopy version of the manual, but, you'd need to verify that one matches your vehicle, and the full set is four manuals, the two shown there plus two more that cover the wiring and the teardown of the differentials, transmissions & transfercase,
Have you considered printing the "digital copy" that you have? It's a pdf file and should be as simple as clicking the print button in the upper left of the screen. I usually just print the pages I need for any given task.