P2 Brake Controller Shows No Trailer Connected with Trailer Connected to a 2004 GMC Sierra

Question:

Hello, I installed the prodigy p2 brake controller in my 2004 GMC sierra, and when the trailer is connected the display does not indicate that a trailer is connected. I watched the video of the 2004 GMC Envoy where the tech pulls down the panel and splices the 4 wires that connect to the brake controller but I did not do this. When doing the install, I used the GM wiring plug that plugs into the fuse box on the lower left of the drivers side of the vehicle. There is power to the controller but it only reads . . when trailer is connected. Also, when I operate the manual braking lever the display reads .nc. . Am I getting no connection to the brake controller from the 7 pin connection because I did not splice the four wires like in the Envoy video? Thanks in advance for any help you guys can lend,

asked by: Mark

Expert Reply:

The 2004 GMC Envoy uses a different installation method than the 2004 GMC Sierra. So you did the installation correctly. GM for some reason does not make the full connections on trucks with the factory tow package.

There may be some connections that you will need to make under the hood and, if not, then you will have to run a wire manually from the brake controller blue wire to the back of the 7-Way. I have linked a help article that covers the under hood connections.

If you need run a wire manually you can use about 25 feet of wire # 10-1-1 sold by the foot. When routing the wire you will go through the firewall, under the truck, and to the back of the 7-Way where the wire will attach in the 7 o'clock position. Be careful to avoid areas that can pinch or burn the wire.

expert reply by: Michael H