Brake Controller Installation Details and Running Wires on a 2002 GMC 2500 Pickup

Expert Reply:

The best practice for running wires through the firewall on your 2002 GMC 2500 HD pickup, is to find an existing opening that has a grommet and use that. You'll also want to make sure that you keep the wiring well away from any moving or hot parts.

In the absence of an existing opening, you might have to drill to make your own. In that case, make sure you are aware of what is behind the spot where you plan to drill, so you don't drill through anything important. You will need to use a grommet, # SWC8055, to protect the wires from the sharp edges created when drilling.

If you are installing a brake controller, be aware that your vehicle already has the wiring in place, you shouldn't need to run anything through the firewall. There is a port under the dash that the controller will plug into using a brake controller wiring adapter, # 20263.

The port is located in the black electric junction box underneath the dashboard, to the left of the steering column and just above the carpet. You will have to remove the cover. The brake controller adapter is plugged into the second slot from the left on the top row. The brake control wiring adapter is used to simplify the electric brake controller installation.

The 4 wires on the adapter will then be butt-connected to the 4 wires coming out of the electric brake controller. In most cases, the factory will have run the rest of the wires to the 7-way trailer connector in the back of the vehicle. We also have an online help page, see link, that explains the installation process in more detail and shows the wiring connections under the hood if they were not completed at the factory.

expert reply by: Mike