2006 GMC Sierra Trailer Wiring | etrailer Fastest shipping available and a lowest price 2006 GMC Sierra trailer wiring guarantee. Expert lifetime technical support on all purchases. Complete 2006 GMC Sierra Trailer Wiring installation instructions and customer reviews. Call 800-298-8924 to place your order or order online at etrailer. How to Install a Brake Controller on Chevrolet / GMC 1999 Vehicles with Factory Installed 7-Way. If you are attempting to install a brake controller on a Chevy/GMC truck (1999 - 2006, including 2007 classic) and your vehicle is equipped with the factory installed 7-Way trailer connector, the only part needed to install the brake controller is the unit itself.