I bought GM kit off ebay, factory kit, came with switch in dash, wiring etc. also comes it code to allow dealer to program it, must run wire to BCM , not to bad but worked for gm plant for 30yrs in repair had that advantage and friend helped
I worked at GM spring hill building the Traverse as the cars come down the line with and unflashed BCM, according to the options the cars are flashed accordingly, if option not on build sheet then no flashing RE: fog lights, auto tailgate etc.