Your Trailblazer should have come with a pigtail to connect a brake control box. You can get one at the dealer if you can't find it. Also, depending on which brake control you have you can buy one that is plug and play with a wiring harness that is made for your application (this is the one I bought and did not need to splice any wires). I might add that the Prodigy is the best control I have used:great: