2004 GMC Heavy Duty Trailering Package Wiring

arroyoseccofarm · June 27, 2004

Whoa! I hooked up my new horse trailer to the plug under the rear bumper. Everything works (brakes, tail lights, turn signals, flashers, running lights) except the interior "auxiliary" lights on the trailer. Trailer dealer said GM dealer needed to do something to the truck. Is there a fuse that I am supposed to know about that I don't know about?

Thanks in advance for your help.

ArroyoSeccoFarm

sonjaab · June 27, 2004

AR.........Check in your underhood fuse center.

There should be a seperate fuse for that and the trailer brakes.

Check your owners manual for explanation..................geo

arroyoseccofarm · June 27, 2004

The manual is vague. Under the hood, in the fuse box, there is a "stud B" in the upper left of the box, when viewing from the left fender. Is that where there should be a fuse?

Thanks for your help.

ArroyoSeccoFarm

sonjaab · June 27, 2004

ARRO.......Check out the "trailer wiring" post I brought up.

It explains what ya need !

arroyoseccofarm · June 27, 2004

Thanks for your help. I'll take another look under the hood.

ArroyoSeccoFarm

99silveradoz71 · June 28, 2004

I know on my 99 Z71, the interior light on my Wells Cargo wouldn't come on unless I had the parking lights(or headlights) on on the truck. Just something to try.

syntheticracer · June 28, 2004

I just went thru this and it is located in the large fuse center under the hood. The fuse is the STD#1 (I think). It is located in the upper left corner of the fuse center. These are the large fuses. The cover states that you need a 40, but my trailer place stated that a 30 would work just file for running accessories.

Hope that this helps.

arroyoseccofarm · June 29, 2004

I put the 40 amp fuse in the fuse box and everything works as it should.

Thanks for your help.

One funny story for you - I went to a Chevy dealership today and walked in thru the "Parts Department" door. I described the problem to the guy at the counter. He tells me I should have gotten the fuse with the brake controller harness packed in the glove box and that if I want another he would have to sell me the whole trailer harness "kit." I ask him what I am supposed to do if I blow the fuse . . . buy another harness kit? He considers that for a minute and realizes how stupid it was and goes to the back room. He comes out in a minute and says he is out of the fuse but that any parts place would have them. I wanted to ask him if the sign on the door was wrong but the situation was already confounding him. I got the fuse at O'Reillys down the street.

sonjaab · June 29, 2004

AR..........LOL>>>>>>>Funny story !!!!!!!!!!!!!

Glad ya got fixed up !

GM didn't give ya that wiring harness with the tow pkg for 02/03?.

They wanted you to pay a extra 45 bucks...............geo

bigdogs · June 29, 2004

I know they didn't with the 03's Here is what the sales manager who sold me my Sierra told me...

"Those items were standard on 01,02 but in 03 GM deciced to save a couple bucks per truck and no longer included them with the trailer pkg. Then in 2004 decided to include it with the tow pkg. I apologize if the website indicated differently But perhaps it was stated as start of production 2003 for the 04 Model year. Those items are available in our parts depart approx. 27.00 for harness and 12.00 for 7 to 4 connector."