[cdru]

I beleive it is to indicate that the vehicle's "alarm" (if you want to call it that) is activated. It's more of a theft deterent then a actual useful feature. It's kind of like putting the "This home montitored by ADT" sticker on your windows to make thieves move on to the next car. Locking your doors with your keyfob should "arm" the vehicle and turn on the light.