Class 2 serial data line ???

Im putting a factory 03 grand am gt monsoon system in my 95 trans am vert . Im pretty clear on all the wiring , but 1 thing . In the 03 head unit there is a wire that the diagram says is a class 2 serial data line . Can anyone tell me what the function of serial data line is in the newer gm radios so I know what to with it .

Thanks

Anybody ever answer this???

The serial data line (OBDII) ties into the body controller. It recieves some info from the BC, but the biggest problem is that it also recieves the VIN#. This is how the theft-loc works. As of now, if the BC VIN does not match the one in the radio, it will not function.
Here's a thread I'm working on:
http://www.fiero.nl/forum/Forum2/HTML/047817.html

Thanks for the reply , I ended figuring this all out on my own . Theres no way to power a 2001-04 radio outside of class 2 electronics . The new radios are turned on my the PCM and outside the car they came in there would be no way to disable theftlock . I even figured out how to get the radio to work in a traditional 12 volt system , but theres no way for me to disable the theftlock because in the new ones its done thru the ALDL with a scan tool . So the GA cd player is basically useless .

My loop hole was using a vibe radio . The Vibe uses the EXACT radios as the other pontiacs ...including the 6-disc in dash reciever . The Vibe doesnt use class 2 and turns on with a normal 12v ign wire , and the theftloc works like the older pontiac radios .