How to Install a Brake Controller on Chevrolet / GMC 1999-2006 Pickups

Vehicles with Factory Installed 7-Way

If you are attempting to install a brake controller on a Chevy/GMC truck (1999 - 2006, including 2007 classic) and your vehicle is equipped with the factory installed 7-Way trailer connector, the only part needed to install the brake controller is the unit itself. The manufacturer provides a brake control adapter that connects to the brake controller and plugs into the vehicle's electrical junction box. This junction box (shown below) is located on the driver's side below the dash, left of the brake pedal. If the factory brake control adapter cannot be found, we offer a replacement (for model years 1999-2002 use 3025-S, for years 2003-2006, including 2007 Classic models use 3015-S). After mounting the brake controller in a place that is easily accessible, your installation is complete.

Custom Fit Brake Controller

Brake Controller Product Image
Locate Brake Controller Adapter Plug Image
The brake control adapter plug is located in the electrical junction box on the driver's side, left of the brake pedal.
Close-up of Electrical Junction Box Image
This close-up of the electrical junction box with the lid off shows several available slots. The brake control adapter is plugged into the second slot from the left on the top row.

Vehicles without Factory Installed 7-way

Step 1 - Install brake controller:

Hardwire the open wires of the brake control adapter to the wires on the brake controller. Plug the other end of the adapter into the electrical junction box (see above). Mount the brake controller in a place that is easily accessible.

Step 2 - Under the Hood:

Remove Bracket in Corner Image
A: Remove the bracket in the corner closest to the driver.
Remove Top Cover from Accessory Fuse Box Image
B: Remove the top cover of the "Accessory Fuse Block."
Remove Lower Cover to Fuses Image
C: Remove the lower cover to the fuses.
Locate Blue and Red Wires Image
D: Locate the blue and red wires. These are normally located next to the fuse block on the cab side. The blue wire has a plug on it, the red wire has a ring terminal on it.
Place Red and Blue Wires and Clip Image
E: Place the red wire over the closest positive post (B). A green 30 amp fuse is needed in the location nearest the positive post to power the brake controller. A smaller brake controller may require only a 20 amp fuse. Consult the brake controller installation instructions and the vehicle's owner's manual. Next, clip off the connector on the blue wire (A).
Placing Gray Double Bonded Wire Image
F: The installation kit provides a gray "double bonded" wire which is really two wires in one. Connect the white wire in the gray housing to the blue wire under the hood. If a hot lead is also needed connect the black wire (shown in red for clarity) to the other auxiliary positive post. A 40 amp fuse needs to be placed in the last spot, closest to the post, to power the hot lead (see picture). If this post is already in use, you may connect the hot lead directly to the positive side of the battery via a 40 amp circuit breaker (provided in kit). After the connections are made, route the remaining length of the double bonded wire to the back of the vehicle, where it will be attached to the 6 or 7-way adapter (provided). Usually the wire is run either inside or above the frame on the driver's side of the truck. Once run, connect the white (brake) and black (hot) to the blue (brake) and black (hot), respectively, on the back of the 6- or 7-way adapter.

Step 3 - The Trailer Connector:

Plug 4-pole into 6-way or 7-way adapter Image
A: If the vehicle is already set-up with a flat 4-pole trailer connector, then plug it into the 4-pole on the back of the 6- or 7-way adapter that comes with the installation kit. The white wire (ground) coming out of the back of the adapter needs to be attached to a substantial grounding point on the frame. After mounting the new 7-way or 6-way connector, installation would be complete.
Find Necessary Wires Above Spare Tire and Wire Colors Image
B: If no trailer connector has been provided, the necessary wires can found above the spare tire. The yellow wire is the left turn and brakes, dark green wire is the right turn and brakes, brown wire is for the taillights, and white is the ground. Often if the loom is cut back, two more wires will be found. The light blue wire provides a lead for a camper shell brake light. The other, a light green wire, is for the reverse lights.
Connecting the Wires Image
C:Connecting the Wires. First cut off the 4-pole on the provided 7-way or 6-way adapter in the installation kit. Quick splices are provided to connect to the wires above the spare. The green wire is connected to the dark green wire on the vehicle; the yellow to the yellow, brown to brown. The white (ground) on the adapter can either be connected to the white (ground) wire above the spare, or it can be grounded directly to the frame.
After installing the mounting bracket with your 7-way or 6-way trailer connector, the installation is complete.

Questions and Comments about this Article

Robert S.

Why isnt the brake controller working after pluggin it in to the electrical box as per instructions. I plugged in the wire harness in second plug and get nothing to brake controlller and the lights to the trailer. I used the wires above the spare time.

Etrailer Expert
Reply from Les D.

Which brand and model number brake controller are you referring to and what is the year/make/model of your vehicle. The first thing we will check is the truck fuses. Then we will measure voltage on the lines to and from the brake controller to make sure the BC is getting power, and if so, does it send voltage to the 7-way bumper connection.



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