Quote Originally Posted by big99miketma
When that wire sees ground it mutes the radio, it is supposed to be for cell phone car kits, but you can use it for onstar also, you could use it for radar detectors, or if it is a Pioneer AVIC series radio on some models it is for bypassing video. But most of the time it doesn't get used.
Thanks for the very informative response. I already repped ya, but mine don't mean shit.