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

Custom Fit Brake Controller

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.

Cover removal

The brake control adapter plug is located in the electrical junction box on the driver's side, left of the brake pedal.

Cover removal

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:

Parts needed:

  1. Brake controller
  2. Brake control adapter
  3. Brake control 7-way or 6-way installation kit

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

A: Remove the bracket in the corner closest to the driver.

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B: Remove the top cover of the "Accessory Fuse Block".

Remove Bracket

C: Remove the lower cover to the fuses.

Remove Bracket

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.

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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).

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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:

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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.

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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.

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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

Paul P.

I got a problem, 2005 chevy 2500 , Everything was working fine till the dogs tore up wires under our 2005 toy hauler, I repaired the wires got the lights and blinkers working again, but I have no trailer brakes with the brake pedal, but I can make them work by pressing the plunger on the brake controller, , is it a blown fuse? 102264

Reply from Jon G.

Were you always able to get the brakes working with just the brake pedal while sitting still? Reason I'm asking is because more proportional brake controllers will not send power back to the trailer if the rig isn't moving because the sensor can tell that the brakes aren't needed. Since the manual override is sending power back to the brakes that's a good sign. In this case you can verify that power is getting to the controller when you press the brake pedal by testing the input wires (one should only get hot when the pedal is pressed), or you can take your rig to an empty parking lot to see if the pedal is working or not. 75327

Tom R.

I have a 2002 GMC 2500. New brake controller thought the old one was bad. The new one shows power when manually pushing lever. But not when applying brake petal. Found a blue wire in rear where it goes into 7 way corroded. Cut and repaired. Still not working. Fuse?? Relay?? 102115

Reply from Jon G.

Are you driving when you press the brake pedal? Usually what is happening in your situation is that the truck is sitting still and a proportional brake controller is being used. Since the vehicle isn't moving the controller senses this and doesn't send power to the brakes because it isn't needed. 75251

Reply from Tom R.

@JonG ok so just sitting still with key on Position it won’t send A signal to brakes in rear? So I need to drive it and hit lever to see if they actuate then? And step on brake to see if I get a reading. Should I get a light on my test light if someone hits brake petal with trailer unplugged with test prong on the correct leg? 75258

Reply from Jon G.

@TomR Right, sitting still while trying to use the brake pedal won't produce any results. As long as your brake controller is sending power back with the manual override (like you stated) and there is power going into the brake controller when you press the brake pedal then you should be good to go. The only real way to test with your brake pedal is to hook up your trailer and drive some so that the controller senses that a trailer is connected and sends back power. I'd try to test out your brakes in an empty parking lot it available just to be on the safe side of things. 75263


I got a PRIMUS IQ brake controller on my 2004 Chevy Silverado 2500hd when I engage controller I get a sh code when controller is set above 6 v. I tried a Tekonsha p3 the screen goes blank and hums when engaged. I removed controller. I got 12.5v to red when I jumper to blue voltage drops to 5.6v. I hooked trailer up to my dodge both controllers work fine on it. Could I have a bad ground, short or bad connection? 97790

Reply from Jon G.

Yes - all of the above. The SH code you're seeing means that there is a short somewhere on the brake controller circuit. This could be the result from any of the causes you mentioned so you need to check all of them and fix accordingly. 72589

Larry T.

05 suburban-I connected the brake controller via the plug it simple adaptor under the dash. I have power to the controller, but it doesn't recognize that the trailer (camper) in plugged in. I put a 30 amp fuse in the dummy spot under the hood, still nothing. I have a hopkins impuse. 97000

Reply from Jon G.

Does the pin in the 5 o'clock position for the 7-Way on your '05 Chevy Suburban show power when you use the manual override on your brake controller? If it doesn't then you might need to make some connections at the back of your 7-Way for the connector to be fully functional. 72586

Reply from Jon G.

Does the pin in the 5 o'clock position for the 7-Way on your '05 Chevy Suburban show power when you use the manual override on your brake controller? If it doesn't then you might need to make some connections at the back of your 7-Way for the connector to be fully functional. 72588

J M.

06 gmc sierra 1500 work truck 4.3l standard transmission No power to trailer connection at junction box, can not locate second blue or red wire. Trailer lights all work fine 82209

Chris C.

My brake controller is not getting power, it use to have a green light glowing all the time now i have no trailer lights, it worked fine a few moths ago. 74138

Reply from Chris R.

If the brake controller isn't receiving power at all then it's somehow lost connection with the battery under the hood. If you used a factory harness for installation it could just be a blown fuse - check your truck's owner's manual for the right location. You also mentioned that the trailer lights aren't working - do you mean the actual tail lights on the trailer or were you just referring to the lights on the brake controller itself? 60327

Reply from Chris C.

Both, the lights on the brake controller and the trailer lights are not working, checked the fuses, there are three under the hood i checked, a big 40 amp and two 10 amp, they look fine, should i change them? they worked fine the last time i used it. 60346

Reply from Chris R.

For both the brake controller and all the trailer lights to suddenly stop working I have to think that a blown fuse (or two) is the cause. It wouldn't hurt to replace those fuses you found just to be sure. There might also be some towing related relays located elsewhere under the hood or in the passenger fuse compartment. Please let me know what you find and we can go from there. 60435

Reply from Chris C.

@ChrisR: Changed 40 amp fuse and 4 15 amp trailer related fuses and the same no power, could the controller be bad and shorting it out or the plug in the back of truck be bad? 61575

Reply from Chris R.

You could try disconnecting the brake controller from the vehicle to see if this has any affect on the trailer lights. The rear 7-Way plug could be bad too, but since the brake controller gets power directly from the battery, it wouldn't prevent the controller from at least turning on. Let me know what happens when you unplug the controller and we'll keep troubleshooting from there. 61590

Reply from Chris C.

@Chris I changed the last fuse and disconnected the brake controller and still no power to the plug, were the brake controller plugs in are 3 grey square fuses does any of those have anything to do with power to the controller? also if i replace the plug i could not see were it connects to under the truck unless its up past the spare tire somewhere. 61804

Reply from Chris R.

Since you still aren't getting any power to both the trailer harness at the rear and the brake controller port, I would honestly take the truck up to a local dealer at this point. Something is off with regards to the factory trailer wiring, so I think it's best for them to take a look. 61927



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