Just replaced my (what was stock more on that in a second) head unit with an aftermarket job, and I pulled two plugs out of the 'stock' unit. The bigger plug had all of the power and speaker wires, no big deal, new head unit works fine (just need to get the antenna adapter). But there was a plug on the drivers side of the head unit that i removed that had maybe 3-4 wires in it. What was this plug? something to do with the anti-theft stuff? The security light in the dash didn't come on, yet, and everything is working properly with my stereo so far, so what is it?

I thought my stock stereo looked odd having the greenish/blue lighting on the buttons/display, and the rest of the car being lit up red. I pulled it out and it said "96 cavalier" on the bottom in paint pen, JUnkyard unit. I dont know if that makes any difference or not, but thats what i've come across so far.