what is the 10 volt wire used for on the radio harness?

 

?? You're probably probing the of the GM LAN communication wires....

 

if you look at the sticky about the wiring diagram there is a wire thats for 10 volt then another wire for the gm lan??

 

I am pretty sure the 10 volt is a reference voltage for the steering wheel controls.

The controls are a set of resistors and the button you are pushing determines a certain resistance and a voltage drop and the radio processes that a know you hit volume up ect.

 

Good call, you're right. The radio supplies that wire with 10 volts, and that powers the resistor network for the steering wheel controls. When I put a new HU in and wired up a PAC SWI-ALP, I had to supply that wire with 12volts so the resistor network had power.

Here's directions from the PAC website:

# Connect the INTERFACE's Green wire to...Pin A9 Dark Blue of the above connector
# Connect Pin A10 White/Black to +12 volts accessory.