Brake Controller Installation on a 2012 GMC Sierra 1500  

Question:

Expert Reply:

It sounds like you are on the right track. Your 2012 GMC Sierra does not have an OEM plug for installing a brake controller, but they did run the wires for you. We do not offer an adapter that would allow you to hard wire the Hayes Energizer III brake controller, but you do have the option of just cutting off the existing plug.

You should be finding the correct group of wires under the left side of the instrument panel you see to the left of the steering column. There may very well be an additional wire, but it would not be used for a brake controller installation. You could have either 4 or 5 wires in the bundle.

Commonly, GMC will use the following colors in its brake control wiring bundle. You will want to check this against the bundle you find, however, as they have sometimes been known to change up the colors without notice.

Red/Black GM wire: 12V battery power, connected to the black brake control wire.
White GM wire: Ground, connected to the white brake control wire.
Light Blue/White GM wire: Stoplight signal, connected to the red brake control wire.
Dark Blue: Electric brake output, connected the blue brake control wire.
Orange GM wire: This would be the extra wire that is not used for the brake controller installation.

As you mentioned, it is true that you might also have to make two connections under the hood. You should find two wires: one is the power wire to the brake control and the other is the battery charge line to the 7 way connector. These wires are both Red/Black and they both will have eyelets on them. They are coiled up under the hood and will need to be connected auxiliary power posts next to the under hood fuse box. You are going to find one of the wires between the under hood fuse box and the left (driver) side fender, and the other can be found under your master cylinder/brake booster assembly. I am including a link to an FAQ that will show you some pictures of the connections, as well as some information on brake controllers in general, if needed.

expert reply by: Sarah L

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