ABS/Auxiliary wire to 7 pin

I am having issues with the trailer abs. After working on it for hours I have narrowed it down to the feed 12v power supply for the aux/abs blue center pin wire. The aux/abs wire reads +/- 1.00 volt with key on. Traced back to the 3 pin connector under cab in the frame rail, same there 1v. My quesion is where does the aux abs blue wire get its 12v from when key is on. After the 3 pin connector the blue wire turns into a black wire non-discript/no markings (same wire gauge) and then gets lost it the main harness that leads to the firewall. If someone could point me to the source I would greatly appreciate it.

 

There are no maxi fuses in the dash and I do not see and fuse box under the hood near the steering column.

 

2006 vnl with 400hp cummins. Thank you for your help.