Well, its not a matter of speculation - it *does* happen.

But you are correct in the sense that high-end technical details are not available. I could not get any information because the chemical compounds used in these coatings (and often the process that gets them bonded) are trade secrets that are avoided in conversation.

Honestly, we should ask out loving sponsor - Jet Hot - to get in here and share what knowledge their legal department will let them mention.

 

Geoff Chadwick:
I agree, it does happen. Far too many stories for them all to be installation errors. I also wonder about the possibility of system changes to sometimes be mis-interpreted. After all, the exhaust system has been changed and it's probable the O2 distance from the heads is different and almost certain the temperature at the sensors is different. I'm not certain but I think the sensor readings are affected not just by O2 concentration but by temperature too. So perhaps, that leaves the ECU having to readjust some learned values. A daily driver may adjust in a few days but a weekend or track car might take much longer.
Just wondering ...

 

and your reason for the problem being fixed as soon as sensors replaced?

just asking.....

 

The sensors are extremely sensitive to operating temperature, but only at the levels encountered in PE mod (WOT). In closed loop, they exhibit less sensitivity to temperature. To minimize problems with operating temperature, the 94 and up sensors are heated.

If the temperature change was significant, the sensor output would be altered (skewed). The PCM could only use the "bad" data from the O2 sensor to alter the A/F ratio. It can't "adjust" to the fact that the temperature has thrown the sensor out of calibration, since the PCM has no way of knowing what the operating temperature is.

 

Injuneer:
Would the ECU (OBDI) immediately accept the new readings (when in closed loop) as a new baseline or use some algorithim to relate it to what it was seeing before? Does OBDI even store O2 history? How about OBDII cars ... aren't they able to use the before & after cat O2 sensors to adjust for changes in the before sensor values and prevent going very lean or rich?

dangalla:
"and your reason for the problem being fixed as soon as sensors replaced?
just asking....."
Perhaps a new sensor meant a new, clean connector? There was a recent post (I don't remember who) that had "bad" readings on 1 bank and poor performance too. I recall they wrote later that they remade the connections and their problems went away. I think they said they heard a nice solid click the second time. Some installations (mine for instance) stretch the electrical lines to their length limits. Others need extenders or soldering extensions to the lines. Quality of the connection could be the problem.

 

I can only guess. But I doubt the PCM keeps track of anything like that. You start the engine, eventually the O2 sensors start to put out a voltage, it goes into closed loop, and the PCM looks at the voltage and makes whatever adjustments are necessary to bring the O2 readings back to an average value of 450mV. It has absolutely no way to know why the O2 sensor is putting out a different voltage than before. That's the problem with contaminated sensors and things like leaks in the exhaust and misfires. The PCM just sees "lean".... has no way to determine what is actually causing the deviation.

As far as OBD-II, I can't find any evidence in the diagnostic charts that indicates the PCM looks at the after-cat sensors to determine if the pre-cat sensors are correct. It looks at the pre-cat sensors to determine if the after-cat sensors are showing the correct range of readings, but not the other way around. And then when it doesn't see the correct level of activity in the after-cat sensors, it has no way to know if its faulty sensors or a faulty cat. So it sets a code for inadquate oxygen storage, forcing you or your mechanic to run the basic tests to determine what set the code.

Just a guess... short of having a GM engineer divulge what are probably some very proprietary design capabilities and objectives.

 

Injuneer:
Thanks for the info. 13-14 years down the from Camaro OBDI / OBDII ... I wonder how much AI the automakers are implementing in the current ECUs? With the huge advances in computer hardware at modest increases in cost there are all sorts of possibilities!