You got me there, Luciano, and I'm really not up on S2s, but I would just remind you that the wire colors for the indicators in the front are the same as for the rear so the wire colors in the harness may give you some clues.
I'm baffled by the "SIDE" label in the headlights on the wiring diagram too. It was my understanding that it's indicators that are sometimes in the headlights but there are separate indicators on the diagram.