OnStar location 2012 Sierra 2500 Denali

[swaneyd]

The OnStar location is behind the HAV buttons.
Take your time and pry off the fake wood plate. There are 9 clips. It feels like it will break, but it didn't.
Take out the 4 screws to remove the lower to levels of buttons and control knobs.
The Onstar box is wedged in there. I pulled and wiggled until it came out. There are 4 cables, 2 white, 1 black and 1 red. I wrapped the red and black in bubble wrap to keep them from rattling around. Plugged in the 2 white cables and the light started to flash green and red.
I paired my phone and made a phone call.
Then I put the dash back together.
It took about 45 minutes.