GMC Sierra Trailer wiring question

[wildbilll]

I have added an second battery to the truck, used a 140 amp VSR to tie them together. I put in an in-bed power outlet (Hopkins 41157 Endurance 5th Wheel Wiring Kit tee' d into the factory X88 plug) to power a 12 v refrigerator/freezer.

I want to isolate the 12 volt trailer red/light green wire that apparently runs from the underhood fuse box to the rear of the truck so it is powered from the auxiliary battery only, not the fuse center so it won't run down my main battery.

I can't find the wire in the underhood harnesses. Does anyone know which loom contains the wire?

Also, suggestions on the best way to switch that wire from the existing underhood fuse box connection to a dedicated feed from my auxiliary battery?

[asilverblazer]

Sounds like it would be easier to run a dedicated circuit from the auxillary battery to the trailer plugs to me. 

 

Check out gm-upfitter to find a wiring diagram.

 

Also, look at the  underside of the underhood fuse box. That circuit is fused there, you can trace it out of the underhood fuse box and intercept it (or - remove it from the underhood fuse box and re-route it) to the auxillary battery.