Trailer wiring harness diagrams W/o internet goose chase

your grounding out some were check wires

TRAILER TOW CONNECTOR-ADD ON - 10 WAY CAV CIRCUIT FUNCTION 1 - - 2 L674 18LG TRAILER TOW RIGHT TURN RELAY OUTPUT 3 L1 18WT/LG BACKUP LAMP FEED 4 A100 14RD/VT FUSED B(+) 5 L678 18BR PARK LAMP RELAY OUTPUT 6 - - 7 B40 14DG TRAILER TOW BRAKE B(+) 8 Z999 14BK GROUND 9 Z999 14BK GROUND 10 L673 18YL TRAILER TOW LEFT TURN RELAY OUTPUT

the wiring harness is the econimical way to go about it; it serves the same function as if you had a tow package. But if you want the Dealer Tow package look, there are multible harnesses that you can just plug into the existing plug under your vehicle

Try http://www.etrailer.com/faq-wiring.aspx. If it is factory installed, there should be a plug in next to/behind the parking brake pedal... at the top. Not easy to see or get to.

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.

Also try http://www.etrailer.com/faq-wiring.aspx. They have a great website with lots of info. With the tow package, there should be a plug under the dash... far left above the emerg. brake petal. The harness that plugs into it should have came with the truck, or you can order one to fit it. Did thew truck come with a 7 pin plug on the back? If not you can order one from the above mentioned site. They also have the wiring colors.

Check the trailer connector for loose or corroded wires that come into the back of it. If the light works on the truck then you have problems with the trailer harness.

You'll need to disconnect the wires from either the truck connector or the trailer connector...
I highly suggest purchasing a voltage checker- it looks like a screwdriver with a pigtail of wire with an alligator clip on the end. The tip of the 'screwdriver' has a point for probing. The light in the probe will light up...makes it easy to trouble shoot without a helper behind the trailer.
Hook the aligator clip to a good positive grounding point on the bumper or frame(not painted).
then pin by pin on the truck connection, stick the probe on each terminal tab.. and write a simple diagram where you find brake, tail, backup, etc...
Then i'd suggest, taking the connector off of your trailer, exposing the wire ends.
Run again thru your diagram and turn on each light of the truck. As you do, touch the wires from the trailer to that specific terminal. (make sure your ground wire is attached on the trailer) you can mark each wire with a piece of tape and label it which is which.
then simply attach your trailer wires according to your diagram to the terminals in the connector... that should get you in business..
hope that makes sense...
That way if the factory wiring harness remains the same, you'll be able to use it with other trailers if the need arises..

If you have amber signal lights & red brake lights, it's 2 separate circuits. You'll need to buy a small converter that you wire into harness to correct that. Not expensive, try autoparts store or RV/trailer sales, should have them.

Hi there;

Here is the wiring diagram for the trailer wiring for your truck.

Hope this helps
Farrout!