H3 headunit stero connections

[Haiminger]

Following my setup (and static noise issue). Can anyone please tell me what is the function of the small connector (the right black one in the picture) that went into my original head unit?

If you look at the picture you will see two connectors. The left one connects to a PAC harness and that connects to my Infill G4.

But the right one (has only one green/black wire going into it) has no where to be connected now.

Any ideas what it did in my original head unit? or where it should go now (maybe it's the cause for the static I'm getting?)

Many Thanks in advance for your help

Haim