Where does electric trailer brake harness plug into under dash

most often that is a power wire for electric trailer brakes or in my case a hot wire to my trailer battery to keep it charged.

the braking system is not installed a the factory just the wire from the plug to the fire wall you need to add the fuse and control box

if its set up for trailers with brakes, it should have small black box under the dash above the pedals; if there is one you can adjust the brake timing to syncronize the trailers brakes with the trucks; if there is not one you can purchase one and mount it and run a few wires

There are separate fuses for the trailer turn signals.Make sure they are good.They are in the under hood fuse block.If they are then check for corrosion in the trailer harness wiring.Hope this helps.Good luck.

most new trailer brake units dont splice into the lines anymore they have vehicle specific plug that connects in line with brake harness under dash or under hood

You have got 7 pin trailer connector that was included in the optional trailer tow package. This trailer tow package also includes an electric trailer brake wiring provision that terminates at a connector located on top of the large body harness connection under the instrument panel to the left of the break pedal, as well as an electric trailer brake pigtail harness and an instruction card that are stored in the glove box when the vehicle is shipped from the factory. You will need to add an electric brake controller of your choice that will plug-in to the harness and that will also give you power on your auxiliary circuit.

Your running lights/marker lights and tail lights are on the same circuit. I all thetruck lights work, the problem is in the plug or plug harness.

Did yo check the fuse panel inside the truck its located on the drivers side dash , you have to open the driver side door, in there is a 10 amp fuse that is linked to rt trailer brakes and rt turn signal for the trailer, if the fuse is good there is a black box under the dash located on the floor on the driver side, just to the left of the break, thats where must of the plug in wire harness is for the trailer breaks!

Ask dealer if it has a towing package on it. If it does, you usually just pop fuse in under hood for electric brakes, and harness to adapt into is usually near or at rear bumper. Even if it doesn't have brake wire, you should still be able to install adapter at rear,for lights etc. which is available from dealer or auto supply places, then you may have to run electric brakes separate.

You may have faulty wiring for your trailer lights. Look under the back of the truck where the wiring harness leads to the trailer wiring harness. Usualy it is a 3 way plug in the harness. Try unpluging the harness from the trailer wiring and just plug the other 2 wires into eachother
Hope this works for you!