Brake Controller Harness | etrailer Install your electric brake controller quickly and easily with this custom wiring adapter. Simply plug one end of the adapter into your brake controller and then plug the other end into the built-in vehicle. Often, a brake controller wiring harness is included with your tow package. This harness plugs into a port beneath your dash and connects to the four wires of the brake controller. Tekonsha Brake Controller Wiring Harnesses Brake Controllers → Tekonsha Direct Plugin Wiring Harness. Simply plug the brake control end of the wiring harness into the back of the brake control and the vehicle end into the automobile's port. Brake controls that utilize the 2-plug style of wiring harness will be identified with the Plug & Play logo.