Mystery Plug, wires and hole in dash

[MASTERBrian]

About a year ago I purchased a 2012 yukon xl denali from a local dealership. There is a small hole that is in the dash, odd location though, as it's on the lower corner and almost obstructed by the arm rest of door. The plug is a flat plug I'm told resembles a brake controller plug. I've tried tracing the wires, but haven't been able to figure out where they go. Under the hood are two? red wires that tie into the accessory bolts on front of fuse panel.

Now I'd go with the brake controller theory, especially after I just found this article.... https://www.etrailer.com/faq-tb-0007...e-Control.aspx
BUT, my Denali comes with a built in brake controller. So why would it be changed out? It still appears to function, though I haven't hooked a trailer to it to find out if works, but messing with the controls it brings up settings on dash. The last mystery wire, I was able to track goes all the way up under the rear of the bed and stops. It's been terminated to nothing. Haven't yet checked it for power or traced it back.

Inside the cargo area something was apparently bolted down and I'm thinking that wire may have provided power. The holes have since been plugged, very professionally I might add.

Trying to solve this puzzle. At one point I had located the previous owners, but everyone told me it would be creepy to contact them and ask.

A friend that has a motor home thought maybe they towed it behind a motor home and had a break controller inside the yukon to control it's brakes??!!

I'll try to get pics if it'll help.