Which wire in the factory trailer is the constant hot? I want to make my pop up trailer hot so I can run lights off truck batteries. I was thinking it was the one marked + but I get no reading with my volt meter. Do I have to do something to make it hot? Thanks in advance.

IIRC, the key has to be on for it to be hot.

Pretty sure there is a plug in the under hood fuse block that needs to be pulled and replaced with the correct fuse... this fuse should have came with the factory trailer brake wiring harness. Cheers.

Not sure about your "06",
but check in the Fuse Block Underhood for a fuse Stud 1. I don't believe your truck comes from factory with this installed. It may be around 40 amps.
When installed, the + terminal should be hot at all times, nothing to do with ignition switch.

Thanks for the info. Currently do not have a fuse in stud #1. I will get one.

2004.5 Duramax. I too have no Aux power at trailer connection (either engine running or off). My concern is owners manual indication on Stud #1 reads "Auxilliary Power (single battery and diesels only)/ Dual Battery (TP2) Do Not Install fuse. There is currently a "blank" inserted in STUD 2 location. And I do have dual batteries. Do I dare install a fuse? What amp rating is the wire sized for?

IIRC, the owners manual is incorrect about the 40 amp fuse to replace the dummy. You should have the fuse wrapped in the factory trailer wiring bundle that came with the truck.

Thanks BTFarm. I have checked wiring from 7 way plug back to where it dissapears from sight and no fuse in factory wiring. I would think that that it has to originate in one of the two fuse panels. Anyone else have any input???? It would be greatly appriciated.

I think the 40amp fuse is wrapped up in factory trailer brake harness. Check your glove box or console. Otherwise, go get one at parts store...

We all (Diesels) have dual batteries. If you want 12v power to the trailer you must install the fuse.

TP2 is the code for the gassers that get the auxiliary battery. Check your glove box, you will not find TP2 unless you have a gas motor.

Not sure about your "06",
but check in the Fuse Block Underhood for a fuse Stud 1. I don't believe your truck comes from factory with this installed. It may be around 40 amps.
When installed, the + terminal should be hot at all times, nothing to do with ignition switch.

My 06' came with the dummy fuse. Installed a 40 amp and was good to go

Thanks all!!! I installed fuse and now have power to charge batteries of trailer going down the road. I can't beleive the previous owner of my truck never powered this up. He pulled a toy trailer that I am sure he would have benefitted from this.
I am suprised that GM made this hot even when the engine is off. Has anyone had problems with drawing down engine batteries when trailer is plugged and sitting for a day or two?

My dad has never installed his fuse. He rarely (if ever) dry camps these days.
My fuse is in, first thing I do when I hit camp is pull the plug. Dead TT battery is one thing...a dead truck battery is another!

I just installed this fuse on my 07 Silverado Classic. Just as described the fuse was taped to the trailer harness. This forum is great!!!

if you get the wireing harness in the dash it comes with the fuse for undr the hood then it is the lite blue wire off to the side of the big plug (but you have to install the fuse under the hood before it will work) hope this helps