A little stereo advice needed...Badly

[David Hiatt]

I have been doing a little research on changing over from a single to a 6 disc Pioneer stereo and a OEM sub/amp. I purchased the Pioneer because I read that the single was not compatible with sub. I get the new one and it has three outputs, but only 2 wiring harness in the truck. I pluged in and everything works. My question what does the thrid wiring harness do, and do I need to get one since everything is working without it, or will it just sound better with it?

Thanks for any help I can get.

 

[Lloyd Curry]

If everything is OEM, I'm guessing the third harness is for the Satellite Radio (Sirius) module operated with the Aux button.

 

[Dingo]

Either satellite or a 6-disc changer.