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As I have heard some differing opinions, I am interested in forum members opinions on what controls/generates the oxygen sensor stoichiometric switching voltage in narrow band oxygen sensors.

As from what I recall when I researched them recently, it's the flow of oxygen ions mediated by the porous platinum catalyst electrodes through the porous zirconium ceramic. The flow is due to the difference in oxygen levels from one side to the other, because they are ions a voltage is generated.

Kinda works in a similar way to a fuel cell.

You will need a solid foundation in physics and chemistry to full understand the mechanism.

Vlads on the money with how they work. I have seen cars that go into car washes and 4WD have issues after water and mud block off the atmospheric side of the sensor. More importantly is how fast the sensor switches.

vald01 & Charlescrown ..Thanks for the response, this also is my understanding of oxygen sensors function by measuring the oxygen level in the exhaust gas stream and comparing the oxygen level in the atmosphere through a hole in the oxygen sensor shell or through the wiring entering the oxygen sensor (this is why measuring AFR at the tail pipe can give a false reading contaminating the sample atmospheric oxygen with exhaust gas).

However there has been a comment that the actual switching of the sensor to maintain stoichiometric is generated by the oxygen sensor, not as generally believed it is the PCM controlling this function this is the area I was looking for comments on.

I believe it's the PCM changine the mixture and the O2 sensor responding which occurs rapidly and is seen when logging. The swing is quiet wide between 200 to 800mv which is pretty much max in either direction.

Absolutely, the sensor is an input to the pcm, the sensor has no control over the flow of air or fuel to change the ratio. it has to be the computer as thats controlling the fuel via injection. It is true that in closed loop the computer is reading the o2 and fueling based off that, so indirectly it is from the o2 but its still the pcm thats doing it, not the sensor directly, or in hardware.

Thanks for the opinions, my understanding is in line with Antus comments, as there are some informed people on this site i just thought I would ask the question. Thanks to all that responded.

You can see how quick the O2 voltage switches in this youtube clip at approx 4.20 minuetes in.

https://www.youtube.com/watch?v=c9hX2hTBfIk