I have installed my brake controller in my 2009 Acadia. I used the factory supplied harness, mounted the brake controller level under the dash, matched-up all the wires except the gray wire and it will not yet work. The user manual says that 2 wires in the engine compartment need hooked-up by the dealer. I have read that some people found that this was not true, that it was just plug & play. I guess I need these 2 wires hooked-up, but can anyone tell me where these 2 wires are and how I can do it myself?