How do i find the wires and install a brake control on a 2008 gmc envoy

If your envoy even had the option of two package and I am not certin that was an option that would include a brake controler wiring harness then in 2008 it would be tucked up under dash around stearing colum. should be colors like blue white red and orange and black wires in a loom or wraped in black tape. if you have the wires athe controler will have a diagram for GM that will tell you which wire color to conect to what. If not you wil need to find the brake light switch and use the wire from the switched side for on wire and a round a blue "10 wire from the controler to the trailer socket and a power wire from a fress sorce like the battery or a lug that is not being used for anything else. Remember to check and be absoletly sure you can tow the weight both toung and total weight safely with the Envoy before attempting to go to the trouble of doing all the wiring. This warning my seem like something you might want to dismiss, but trust me there is a lot going on when you decide to tow. I mention this when you start talking about putting a brake controler on a lighter SUV that might not be capable of pulling a hevy load. The book might say 7k towing capacity, but realisticly and comfortably you will find it is much less. I do not know off hand the ability of the Envoy, but be tottaly sure before you venture out.