What is most likely the cause is just a short or broken wire. The best way to check is to take off the inside panel - then with the tailgate down, close the latches on the sides with your fingers. Then carefully put the window up with the gate down - this will give you much more access inside the gate. Inside you'll see the master cylinder - when turned one way or the other is pushes little switches in. You might try pushing them with your finger - just to test (this little relay switch might be shot also). Then I believe there is only a few wires running from that switch, you can trace them back just by looking for faults or use a voltage tester. Hope this helps a little.
