There are several connectors around the bike that are not used. Intended for GPS, alarms and other factory devices. You can check these to see if they power up when the key goes on or if they are powered all the time and use. Matching plug in connectors can be purchased from BMW (look over the electrical section in the Max parts fiche for your bike or one near in years) The one you have found may be for a second horn. Somewhere around 2009 the harness did not have a second horn connector any longer. The dual horns sound really good.