If the 2004 GMC Envoy came with a tow package, then there should be a trailer brake controller harness. It would be located up under the dash near the brake pedal.
It isn't there, Dodge didn't wire the Dakota with one. You will have to wire the brake controller your self.
The brake controller wiring harness connector for the 2005 GMC Envoy is located under the dash on the driver's side of the vehicle. Look for a connector plug not connected to anything, next to the hood release latch.
There is no harness persay. It appears that GM didn't put a plug in these vehicles so there is no plug-n-play harnesses. The wires are up in the dash and have to be spliced to a brake controller. A friend found this and sent it along. It shows the wire location and basic installation process.http://www.hobicus.com/bartonmd/Trailblazer%20Brake%20Controller%20Install.pdf
There is no harness persay. It appears that GM didn't put a plug in these vehicles so there is no plug-n-play harnesses. The wires are up in the dash and have to be spliced to a brake controller. A friend found this and sent it along. It shows the wire location and basic installation process.http://www.hobicus.com/bartonmd/Trailblazer%20Brake%20Controller%20Install.pdf
If you want trailer brakes you need a brake controller.
There is a connection issue between the trailer brake controller and the trailer.
You need to purchase the add on harness from the dealer. This harness plugs into one of the junction blocks located under the driver's side of dash above your left foot area. The other end of the harness attaches to your trailer brake controler. The trailer brake "blue" wire in back is folded back and tucked in the rear harness on the left side of the rear frame rail. You may have to drop the spare tire to expose it and connect it to the trailer connector plug.
It may not have one. Trailer brake connections are not usually included in a tow package. Check with a GM dealer to find out. If equipped, it should be wadded up under the left side of the dash by the parking brake.
By following the instructions that came in the box of the new trailer brake controller.
The brake controller has to be hooked up to a power source. The controller also has to be hooked to the brake switch or tail lights, then to the plug for the trailer.
When one is using a trailer on their car, an electric brake controller measures the car's braking speed and adjusts the electric braking power of the trailer to correspond. This helps avoid collision between trailer and car.
if you have a plug on the back of your truck then there is a blue plug over top of the emergency brake pedel on top of the 50 way wire harness and your truck should have came with the plug for the electric brakes in the glove box and the wires are marked as to where they go where you hook them to your trailer brake controller i hope this helps you Allen if you have a plug on the back of your truck then there is a blue plug over top of the emergency brake pedel on top of the 50 way wire harness and your truck should have came with the plug for the electric brakes in the glove box and the wires are marked as to where they go where you hook them to your trailer brake controller i hope this helps you Allen