Ya gotta be kidding me...
Open rear driver door
grab seat right at the shoulder
pull back and look at the big GM connector
this is the termination point of the rear harness
It'* not a "factory cd harness" this is what you get
with base trim. Continues on into the "integration unit"
if memory serves as well as speakers...
when you see a box marked so this is a bus termination
So if I have the changer option the factory harness
I promise it'* no fox hunt....
BUT it is just wiring.....
a point of origin INTO the system
There IS factory input.... 3 wire
There is NOT interconnect for it
(no available connector/low level/etc.)
There'* 12v switched in that bundle IF
if you can get the head unit into aux mode without
having classII databus communication
Said from the beginning one might possibly "hack" in
an input - the head be easiest but the wiring terminates
in the rear at that big fat GM connector behind the rear seat!