New HU install, extra black plug?

[jayoldschool]

Installed a new Pioneer HU today. Any idea what the extra black plug is that went into the stock HU? The small square one that was next to the big rectangular blue plug. No place for it on the new one's harness. System seemed to work fine without that plugged into anything, but I only tested in in the garage, didn't start car or check other center stack functions.

[BenWA]

Here:

That second black connector is for the remote 6 disc CD changer that was installed with the navigation systems on the Vibe and optional on others. I have it on my 03 GT and when I installed my son's base radio in it, since the stock nav screen was dead, I plugged in the second connector into his radio and the cd changer works just fine. But all you need is the adapter for the first connector to hook up an aftermarket radio.

More info here: viewtopic.php?t=44405