**URGENT** Can anyone help by telling me what the connectors are for on the back of the VT Calais stock head unit do. The large one of course is for the main wiring harness but there is another smaller connector above the larger one that is not connected. I am trying to connect steering wheel controls but the wiring I pulled from a VX vehicle had the controls running from the main harness connector and no sign of what this smaller harness does. Is this smaller connector for installation of the rear subwoofers possibly? Any help from the audio gurus amongst you would be greatly appreciated.

Before you all ask I have tried to download the wiring diagram for VT but it is an excel programme and will not open for me as I dont have excel installed!!