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Trailer plug wiring tip on Silverado and GM trucks

Discussion in 'How-to Guides' started by BigDogTruck, Jan 10, 2011.

  1. BigDogTruck

    BigDogTruck New Member

    This is a tip for those who are wondering why there is no POWER to your trailer hook up plug.
    I recently purchased a new 2010 Chev Crew Cab, 4 x 4, LTZ, White Diamond Edition. It is loaded and has a trailer hitch and electrical hook up with the factory installed 7 flat pin receptacle. I was doing some additional splicing into the wiring system at the trailer hook up harness for a LED Light bar and also aux. rear back up lights, both requiring a 12 volt power supply. After hard wiring all my connections for tail lights, turn signals, and brakes, I also needed the 12 volt power wire. Which in this case is the red wire going to the trailer hook up plug. No problem until I could not get power to the wire for some odd reason. I did a search on this website and found some information, but it was vague, poor grammar and mis-spelled words that led to further confusion.
    So I did a Google search for trailer wiring on a Silverado. This website came back as my much needed answer, with pictures too.
    www.etrailer.com/faq-brake-control-gmc-sierra-chevy-silverado.aspx
    Low and behold the answer: There is a wire under the master cylinder all taped up with a electrical lug on it for the power wire to the trailer plug. Also to the right of that on the other side of the fuse box, is another wire taped up for the brake controller. These two wires get un-taped and run to the fuse box after you take off the fuse box lid. In front there are two threaded studs there without nuts. One is a M8 and the other is a M6 metric threaded stud post. I had to slightly ream out the electrical lug to fit over the large stud. I also had metric nuts in stock for the threaded studs. Once I attached the wire to the large stud and secured it, I had power to the rear trailer plug. GM does not make the connection from the factory. Many have wondered about why there was no power to a power area already wired and thought ready for use. This saves a trip to the dealer and perhaps a charge for this service.
    Hope this helps someone in the future! I did not have a camera to take pictures but the website stated does have good pictures of what I found.

    Good Luck with your truck.:great:
  2. Als09Sierra

    Als09Sierra New Member 1000 Posts

    Thanks for the post. Great info. I haven't towed yet, but am glad to know how to hook-up the electric for the harness.
  3. aloxdaddy99

    aloxdaddy99 New Member 1000 Posts

    Big Dog I am trying to hard wire my recon light bar. When you wired up yours did you splice the light bar into the trailer wiring? If so have you hooked up a trailer with the lights? Did you have any issues with either lights this way. I found a diagram for the 7 pin harness. I want to use this for the power to the bar. Any help would be appreciated.
  4. stephan

    stephan New Member 1000 Posts

    That's some great info Big Dog. It's going to help a lot of people. Thanks for posting it.
  5. BigDogTruck

    BigDogTruck New Member

    Wiring Help

    Hello there, Glad to of help if I can. I wired all my connections for the Recon light bar into the trailer wiring harness just behind the factory plug. The wiring harness just unplugs from the back of the plug assy.

    Once unplugged from the trailer hook up, untape all the wires so you can get to them easy. Use a electric probe to find the wires you want. Once I located all my wires and hooked them up, I checked them out to see if all works. Once that all is fine, I soldered all connections. Remember the "Hot" wire is not hot without connecting the wires to the power box under the hood if no one has done it before. My truck was new and it comes from the factory "Not" connected.

    Hope this helps. No problems here still working fine. I have a tester for the trailer plug and it is working fine, so my trailer in the future should work too.

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