USB Charge wire from deck?

I tryed getting a answer to my question in the Audio section, I have seen alot of techical discussion in this fourm. Just wondering if there might be someone here "in this Fourm" that dosen't visit the Audio fourm that could help me with my Quest.

What Im looking for is the wire that come's off the back of the head unit that supply's voltage to the USB port under the arm rest.

I want to make the USB port a constant power so that I can charge 5v even when the car is off.

If I can find this wire at the back of the head unit I can save a bunch of work taking the car apart.

Im willing to take pictures and do a DYI thread so the information is shared.
Thanks for anyhelp you can offer

 

I got a PDF of the raido wire harness anyone know how I can post it here. So we can go over it

 

If you click on the link you can see a PDF version on the Wire diagram.

Again Im looking for the wire that powers the USB port
http://3guns.com/25.pdf