I just bought a 3500 Silverado and can't figure out how to get battery power to the 7-pin connector on the back of the truck. I found a red wire labeled "aftermarket trailer power" taped up next to the battery and attached it to the stud that is fed by F63 (trailer battery power). I still don't have power to pin 4 of the connector. Any hints from anyone who has an '08 GM truck?
ED

Sorry, I just realized this is probably the wrong place to ask this. I didn't see the tow vehicle topic.

Although I'm not a GM expert by any means, there's every chance that they use a battery isolation relay to shut off 12VDC to the trailer when the truck's ignition is off. If so, you may find a battery isolation relay in a bag in the glove compartment with installation instructions - the manufacturer usually doesn't install this relay in the power distribution center (underhood fusebox) unless it's going to be used.

I've linked this thread up to the TT & 5th Wheel - Towing section so that you might be able to get a response from someone other than me - you know, someone who knows what they're talking about.

Rusty

Rusty,
Thanks for the response, but I didn't find a relay and looked at the picture of the underhood fusebox and didn't see a place for one. Is it possible that the truck senses when a trailer is connected and then sends power to pin 4? It would have to be done by the Integrated Brake Controller system.
Ed

Ed,

I've probably speculated too much already. I'll defer to one of the late model GM folks to come along and comment.

Rusty

Hello evan0810....First thing to do is return the truck to the dealer for a solution, any messing around my interfer with warranty.

GM has two fuse systems for the trailer package, that is to say, a blown fuse on one side of the truck will not interfer with the function of lights on the same side on the trailer, or may work on the trailer but not work on the truck. The seven-way plug is fused independantly of the truck lights.

make sure two wires are connected. then you add a 40 amp fuse on the far left of the under the hood fuse box

I only found the one red w/ blk stripe wire taped up next to the battery. The 40A fuse (F63 in a diesel) is already in place. I didn't see a second wire. Where would that be?

We bought a 08 Tahoe yesterday and are asking ourselves the same question. The manual says to connect the red battery wire located in the fuse box. Its there but, the battery is way on the other side so I don't know where to connect it? The manual also says the blue brake wire located in the same area should be connected, however, I can't find it?
I use a Prodigy brake controller and I'll have to go to camping world to buy the pig tail and hook it up under the dash somewhere.
If anyone is towing with a Tahoe I'd appreciate your input as well.
Sorry if I high-jacked your thread but, I have a similar truck, maybe someone can help?
Thanks

The red battery wire gets connected to a threaded stud that is in the underhood fuse box. Which one is determined by which is connected to the fuse (40A probably) that is labeled for trailer battery power.
That is what I connected on my Silverado and it still doesn't work. I'm thinking that there may be a bad connection at the trailer plug in back.

I found that there are two red wires under the hood. There is one right next to the fuse box, Hot side of stud. The other wire on our Tahoe was located under the master clynder and it was also wrapped externally of a wire bundle and that was the negative side. Smaller eye hook.
Hope you can find your other wire. Good luck!

'evan0810' -- suggest you PM "rockintom" as he's our resident GM guru on the Excel Forum.

Subfan,
Go to your dealer and ask for Tech Bulletin #06-08-45-008A. It gives directions for adding a brake controller and supplying power to pin 4 of you trailer connect plug.

Ed
p.s. You can google that document and print it out for yourself.

quote:

Tech Bulletin #06-08-45-008A

Thank you very much for the information. I found everything I needed.