Outdoor 3-way motion sensor on a low volt circuit?
Even with the great lack of detail in the question as it currently stands, normally to have &quot;a motion sensor at each end&quot; you need new/additional wires running all the way from one end to the other. The motion sensors need power all the time, so you can't have one at the end away from the current power source without running new wiring for that.
Beyond that, hard to say given lack of detail in the question.