I've looked underneath the dash, to the left of the steering column, in the vicinity of the emergency brake pedal and even went so far as to remove the trim panel to the left of the emergency brake and cannot locate the harness. The vehicle is equipped with Tow Haul so I'm assuming it should be pre-wired with the harness. Anyone have any suggestions?

It will be taped tight to the side of a Main Harness leg, not dangling loose. On Armadas and QX56's they're usually way up there.

That's what I read, but couldn't locate it, I'll give it another look, up higher as you mention, thanks.

I just found a thread from June 2018 which actually had a picture of the harness taped to the main leg as you mention, looks like its taped to the reverse side of the harness which might explain why I couldn't locate it initially. Apparently I was looking on the wrong side, found it!