It goes to the red light on the bumper, two weeks ago the same thing happened to me but the wires got ripped when i was driving 8 inchs of wire was missing and light broke too. Had to do a pigtail to make the light work and replaced the light too.

 

two years ago the pass side actual light broke and I was dragging around a hunk of slushy ice, last year the drivers side wire side of the clip broke. I see numerous xB's driving around with the same temp fix i had of tucking the loose wire into the rear hatch and closing the door on it... must be a wisconsin thing. I bought the parts cheap from the local dealer and wont fix it until I decide to sell it. Not worth fixing every year, just zip tied the wire up under the bumper for now.