The system is designed to read the Oxygen sensor under certain conditions and temporarily change the air / fuel ratio. The closed loop circuit has a very limited operating range, which is only in effect while holding a steady speed at certain rpm's and throttle positions. In this limited area, the stock system (with or without the Power Commander) will gradually and temporarily lean out the air fuel ratio in an attempt to achieve an air / fuel ratio of 14.7:1 (stochiometric). The Oxygen sensors can be disconnected but this will trip the F.I. dash warning light.