Rob, my control box is under the passenger seat I think. I came across it recently. Mine is the TVSS system. It's only the knock sensor I think that is adjustable. Opening a door for example is just a straight signal.
I cant say what is causing it to go off, but once it starts to go off then it keeps going off every 20 or 30 min even if I reset the alarm and open and close the door. My theory is insects, air pressure build up sounds possible too. Does the box say alarm on it? If not how will I know its the alarm?
Found it, it was near the handbrake between the seats. There were a couple of boxes with TVSS written on it which I assume means Toyota Vehicle Security System. One had a rubber grommet which when removed gave access to an adjusting dial. Using a small flat screwdriver I turned it down to "minus" and lets see what happens. So far it has lasted 1 hour without going off