what is this for, and how does work. been watching it on my scan gauge II but can't figure out what makes it open and close.

Thanks

 

O2 sensor(s) is monitored by ECM. When cold, it uses "open loop" control as sensor readings would not be accurate until heated up. Then it switches to closed loop where fuel mixture is impacted by the O2 readings (and other things). Under other conditions, like WOT (wide open throttle) and rapid close of throttle, the ECM also drops out of closed loop because under those conditions you want to ignore the O2 control. Extended idle might see drop out to open loop, if O2's cooled down below a certain point. All of this is geared toward maintaining a balance of 14.7 pounds of air to 1 pound of fuel mix, and reducing certain pollutants that will kill us all, leave the earth barren and scarred, roast polar bears, and make life very unhappy in places like LA.

 

Man your crazy!!! that was a hilarious ending to a very cool response, I have noticed that when I get on it (WOT) and when I let off the gas it goes into open loop, which I now know just says ignore the O2 sensors because the driver could careless about fuel economy. so would it be right to say that staying in closed loop as often as possible would give u the maximum fuel economy?

thanks

 

Yes, and control those horrible gases that some how failed to kill all our ancestors who drove big block Detroit iron with two four barrel carbs and could pass anything on the road but a Texaco. On the other hand, there were a bunch fewer of them. When half of China starts driving, what will happen to the world wide cloud of yuck?