I don't believe that the US S1 version has a ring terminal coming out of the forward harness. Should be easy enough to find though. Take a multimeter, set it to resistance (ohms), connect 1 probe to the ring terminal and probe each connector pin with the other probe. You'll have your answer in 5 minutes.
Now if I had to guess, it is a ground connection, But I would not hook it up to my bike until I was certain,