Another crazy problem

So I installed a new HU in my 2000 Neon and everything went fine. I'm just a little confused on something I found though. The radio had the standard wiring plug which i connected but there was also another wire apart from the harness (purple/yellow) that was directly connected to the radio. I looked up the wiring diagram and this wire is not on there! I've looked at a few different diagrams and its no where to be found. I asked on some Dodge forums and they don't know what it is either. I don't have a factor amp or CD changer. Anyone have any ideas? Its not really important but since 4 of my speakers don't work maybe this has something to do with it?

might be part of some security system

Nope. I have the bone stock Neon. no power locks, windows. Just a random phantom wire that doesn't show up on wiring diagrams. Weird huh?

Are you the original owner?

Are you the original owner?

No, but I bought it from the original owner. This isn't some aftermarket wire. It came stock because it has a connector on it that plugs directly into the stock radio.

You should take a picture of it and where it plugs in on the stock HU.

a wire for an automatic antenna ? Try seeing if there is some condition that the wire puts out some kind of voltage. If that doesn 't work, plug up the power and grounds to the stock radio and see what it takes to get a voltage from where the wire plugs into the radio.

did your stock radio have a speed sensor to make it louder as your car sped up? my f150 had one that i didn't re use on the new hu.