03 1500 Trailer wiring question

[10drum]

Gettings and Merry Christmas, I recently purchased an 03 GMC Sierra 1500. It did not come with a tow package. Is there a harness that can be plugged into the distribution point near the spare tire? Also, will I need to install a trailer brake module, and if so what is my best option?

Thanks for all replies.

[greasemonkey]

If your truck has the factory 7 pin harness with a round plug above the spare tire, all you need is something like this:
https://www.etrailer.com/Custom-Fit-...id=20031310944
If your trailer has electric brakes, you need a controller. I bought a Curt Triflex, but there are many like it. Tekonsha appears to be the most popular. Mine is a proportional controller instead of time delay, basically it applies the brakes as needed to match the tow vehicle instead of applying to a preset tension. Infinitely smoother stops this way. You can hardwire it yourself or get an adapter harness to plug into the distribution panel under the dash. Mine came with the adapter harness.
https://www.etrailer.com/multi-produ...7874&hunter=bc
It has 4 wires: red, blue, black, and white. On mine, black is 12v, white is ground, red is stop lamp signal, and blue is trailer brake control. This is where it gets weird...depending on how your truck was wired from the factory, you may need to run some wire. My underdash panel was pinned for ground and stop lamp signal; however, the trailer brake control wire and power wire were not there. I had to cut the connector harness and run a separate 12v wire to my fuse box under the hood (with a 30 amp fuse inline). When you take off your fuse panel cover, you may have a blue wire dangling there. That is the trailer brake control wire. Run a 10 guage wire from your controller and connect to this wire. If you don't have this wire, you will have to run one to the back to control your brakes.
Hope this helps.

[greasemonkey]

http://www.pirate4x4.com/tech/billav.../tech/Prodigy/
This helped me out quite a bit on my install, though it follows a truck that has the factory tow package and yours will differ a bit as far as the power and trailer brake control wiring goes.

[izzy_Britton]

Long story short, what greasemonkey says will certainly work with probably a lot less work than the long story...

long story, YES. there is a harness that plugs into the bottom of the under hood fuse box. you would need to remove the non-tow package harness and install the harness for the tow package. the wires run from that fuse box to the tail lamp distribution box on the rear most cross member and it includes all the wires for the fuel pump, tank sending unit, emissions crap under the bed and a couple grounds. it is easiest to either lift the cab and the bed off of the frame to replace this harness or it is necessary to drop the tank.

I am sure that if i did some digging i could find more info on how and where what wires go from the distribution block on the rear frame crossmember to a trailer plug... but if your going the cheap simple route get a walmart trailer kit and a test light and have the wife press the brake pedal when needed until you find the correct wires, splice and be done.

greasemonkey points out a really nice system, but it is all dependent upon whether or not you have the tow package harness installed all ready and just havent known exactly what it is that you was looking it. the first link greasemonkey supplied is a nice bit of kit. walmart carries a similar item that is plug and play and is a direct replacement for the OEM connector that even twist locks into the appropriate fixture on your tow hitch if you have one.

keep us posted.

-Izzy

[greasemonkey]

Good point, I did make some assumptions on his particular setup being similar to mine...I have a bit of a bastard truck, some stuff is pre wired from the factory and some isn't. If you have the round plug over your spare tire, I would bet you have the blue wire running to the fuse box (assuming it hasn't been run all the way to the under dash connector...) Personally, if it does not have the blue wire pre run, I would run that single wire instead of replacing an entire harness. I am lazy though..
I think I actually bought my connector at Wal Mart too, years and years ago, but it is the same one I linked too.

[10drum]

Thanks for the replies. I pulled the spare tire yesterday and found a pigtail above it with a 7 pin receptacle. There is a blue wire on the plug.

[TonyD2]

Morning' all. Just a bit of confusion here on my part. I have a '99 Silverado Z71 and have the round 7 pin plug on the hitch.[all factory by the way] The wife and I are very seriously looking at a medium travel trailer. With that being said, there is a extra wiring harness under the seat with an in line 30 amp fuse. Owners manual no help at all on where to plug this in. Can anyone guide me as to hook up and what else I may need to do? Brake controller etc. Thanks in advance for any help.

[greasemonkey]

http://www.pirate4x4.com/tech/billav.../tech/Prodigy/
With the factory tow package, your life is easy. Personally, I would buy a brake controller and a pigtail and ditch the factory pigtail you have. That way, you can just plug the new pigtail in under the dash, plug controller into pigtail, and put the fuse in the box.

If you go to etrailer, you can put in your vehicle info and they will match you up with controllers and harnesses. I used a Curt proportional controller, it is a nice unit and easy to set up.

[fun in dirt]

Originally Posted by TonyD2

Morning' all. Just a bit of confusion here on my part. I have a '99 Silverado Z71 and have the round 7 pin plug on the hitch.[all factory by the way] The wife and I are very seriously looking at a medium travel trailer. With that being said, there is a extra wiring harness under the seat with an in line 30 amp fuse. Owners manual no help at all on where to plug this in. Can anyone guide me as to hook up and what else I may need to do? Brake controller etc. Thanks in advance for any help.

No idea what the extra harness is ... maybe something from previous owner for radio amp or such?
Since you have the factory 7 pin plug at back your good. Brake controller in cab is all you'll need & also tell them you need harness for '99 truck.
This will plug into empty port on elec box down there on firewall by emerg brake & wire that to back of brake controller.

[homemade87]

Originally Posted by fun in dirt

No idea what the extra harness is ... maybe something from previous owner for radio amp or such?
Since you have the factory 7 pin plug at back your good. Brake controller in cab is all you'll need & also tell them you need harness for '99 truck.
This will plug into empty port on elec box down there on firewall by emerg brake & wire that to back of brake controller.

Just for reference . When a new truck came with the tow package GM also included a small harness for the controller . It would plug in under the dash where Fun had mentioned . The harness would only have plain ends on the other end to wire to a controller of your choosing . This harness was usually in the glove box , at leased the ones I seen was . My truck came with one .

[TonyD2]

Homemade, that sounds like the harness I have. I do have the 7 pin plug on the hitch, 6 outside and one in the center. The extra harness I found has an almost rectangular plastic plug and bare wires on the ends. I can make out 1 or 2 of the tags, but wasn't sure where to plug the plug into. Thanks everyone for the info and I will look into these ideas over the weekend.