I have a 03 5.3 Silverado with the towing package I pull my 99 Z28 with and I have a few questions. Do trailer brakes work through the plug (the adapter I plug in at the hitch) that I got with my towing package? Or do I need to buy a new adapter for my brakes to work. I just bought a box and I have the wiring harness that came with my truck and I just need to know if I need anything else.
My trailer has brakes and the wires run to the front but it doesn't have an end on it. So we have been using it without the brakes. I don't know how the trailer wires hook to the truck so the brakes will work. Will it have 2 different connections? Brakes on one connection and the light on another? Or does the brakes work of the 4 prong connector that plugs in at the hitch? I know I completly sound like I have no idea what I trying to say (lol, maybe I don't?) but I'm hoping someone will understand what I'm talking about.

 

I believe that the trailer brakes for the truck work through the 7 way recepticle on the hitch, then obviously the controller in the cab. I picked up a factory hitch right after I bought my truck in July and it came with a 7 way, and the harness to connect a controller to the wiring under the dash. Since your truck came with a factory towing package, you should be good to go. The wire for the brakes is a lighter blue colored wire.
The trailer lights/brakes are through one 7 way connector, it seems like you may just need a new 7 way end for your trailer.

 

You need a brake control for the cab. You can get a harness with the brake control but there should have been one in the glove box if you have the trailering package. Sometimes I think the dealers pinch the harness and sell them or the service guys do. You can connect the brake control to the harness and plug it in under the dash to the left of the steering column. There is a black plastic cover that you remove and plug the harness in under there.

You need to wire a 7 way connector to your trailer as mentioned. If the connector on your truck is 7 way then you should be good to go.

 

If your trailer has brakes and only a 4 pin connector, you need to get a 7 pin connector for it. They arent that much and come with instructions that are easy to understand.

 

Sometimes the Aux power out fuse needs to be installed for power output to the harness even through you have the tow package. On my '03 the fuse was under the main cluster under the hood.

 

Thanks guys. I bought the box that you mount in the cab and I already had the harness that come with the truck. That trailer wiring is what had me confused.