[sewell94]

Well there are 2 types of simulators, the mechanical kinda, basically like the spark plug fouler trick(which does work on some vehicles), and electronic ones, that actually plug into wiring harness and take the the place of the secondary o2, there only a few wires, which makes it very simple to wire up. They give a certain voltage to the ecu just like a secondary o2 to make the ecu think there is a functioning cat.