You're talking about the inertia cutoff switch, right?
Mine is close to the passenger side kick panel, but it's not behind it. It's next to it, I think I had to pull back the carpet a bit. It's about same size around as a AA mag-light and has a red reset button on top. I just disconnected the wiring harness from it and let the truck run till it died and then gave it a few more cranks for good measure.