Connecting a trailer brake controller in a GMC Envoy


My Envoy came with a towing package & there is a wiring harness under the dashboard on the driver’s side. The wires terminate in a gray connector about the size of a pk of cigarettes. Snapped into the connector is a small black box part #12450284. It also says on it : 2/4 w/opt Trailering & DOT ACDTRIDON (1564B5).

To install a trailor brake controller, Do I remove this black box & attach the brake controler in it’s place or leave the box there & cut the brake controller wires into the wires going to the gray connector?


That is a heavy duty flasher module GM installs to accomodate vehicle AND trailer lights. I would think that any trailer brake controller from a reputable company would not require any wire cutting and would have explicit instructions on how to install it. Do you have a manufacturer and model number for your trailer brake controller?

Here’s a website dedicated to the Trailblazer/Envoy platform. There’s quite a few smart folks over there that are very familiar with this platform. Click on this link to go there:


In front of your left foot is a box with a cover.

Remove the cover and plug one end of the harness into it.

The other end goes to the brake controller.

I use a Prodigy bc (highly recommended) in my Tahoe and found it’s a simple hook-up with the GM trailer wiring harness from the bc to the box.

Make sure you mount the bc according to instructions though.