It is an air/fuel ratio sensor, but not a wideband like the majority of aftermarket sensors. Aftermarket sensors generally go from 10:1-20:1 (https://support.haltech.com/portal/e...ional%20engine!) where as the Toyota sensors go from 12.5:1-18.5:1 (https://www.autoequipment.com.au/ima...20Part%203.pdf).

Air/fuel sensors and oxygen sensor voltages will fluctuate. You know what isn't supposed to fluctuate? The oxygen sensor that is downstream of a properly functioning catalytic converter. That voltage should fluctuate less than the upstream sensor (air/fuel or oxygen). So, yes I do still think that the sensor positions are switched on whatever OP is using to look at live data.

Where did I tell you it wasn't an air/fuel sensor?

Source number 1 confirms it reads from 12.5-18.5:1 which isn't as wide as the normal 10-20:1 range

https://support.haltech.com/portal/e...ional%20engine!

You're just being obtuse at this point.

Wideband, Wide range, AFR sensor, air/fuel sensor, etc., they're all words describing the same thing: a sensor that can accurately report what the actual AFR is. The sensing range of different sensors may vary somewhat, but it's immaterial to the conversation at hand, and debunks your original assertion that OP's scan tool is switching sensor 1 and sensor 2. His scan tool is not confusing anything, it is reporting the correct values for the respective sensors.

What would you call an air/fuel sensor with only 60% of the sensing range of most wide band air/fuel sensors? I wouldn't consider that a wide band, but clearly you do.

You have your opinion and I have mine in that respect. I have never seen my rear oxygen sensor readings fluctuate the way that OP shows. I have California emissions as well.

And none of this has any bearing on your incorrect assertion that OP's scantool was displaying the wrong values for the sensors.

I'm sure the evidence to support your opinion is "easily Google-able" as well, right?

You can't even compare rear sensor readings since your rear sensor is emulated according to your signature.

I mean, I've already posted the graph showing what the reported B1S1 voltage correlates to for AFR. Like I said earlier, his graph needs to be rescaled so that we can see more resolution in the 0.4v to 0.8v range. But based on what he posted, his front sensor generally seems to be in the correct range.

What evidence have you provided backing up your erroneous claim that his scantool is screwing up?

I swapped out rear O2 sensors long ago and didn't swap over my simulator. I just live with the CEL (P0420), especially since this isn't my daily driver anymore. I left the link in my signature so others could find the How-To to build their own simulator.

StackPath

"The air-fuel sensor is going to have little humps when graphed. The post-cat oxygen sensor paired with it should not oscillate, but instead stay pretty steady somewhere between 500 to 700 mV."

Which sensor description matches the voltage readings shown by OP? Seems like the sensor 1 shown by OP is pretty steady which matches the post catalytic converter voltage readings described here which match what I see when viewing data with pirated techstream. Also, the post catalytic converter oxygen sensor is the main contributing factor in determined catalytic converter efficiency for P0420. I don't know the range because my 2000 FSM link isn't working but I would suspect IF the voltage swings shown by sensor 2 in OP's data were actually for sensor 2 then a P0420 would set.

You sure do have selective reading...

"Before the catalytic converter, the oxygen sensor will zigzag up and down. To the contrary, the air-fuel sensor will be at a stable voltage. The post-cat oxygen sensor will be a straight line if the catalytic converter is good in most cases."

OP has an AFR sensor in front, so like your source stated, the reported voltage should be a stable voltage. In OP's case, his rear O2 sensor is oscillating, so guess what the conclusion is? He already has a P0420 CEL, so we can conclude that most likely his catalytic converter is operating below the 95% efficiency threshold that the ECU looks for. Not that his scantool is bunk.

You're right. I forgot OP had P0420 already. I don't have any problem admitting when I'm wrong. I still can't get on board with calling it a "wide band" though.

Yes, it is still a wideband sensor. A narrow band sensor has about a 0.2 range, and around 30x that is pretty wideband by comparison.

The extra range of a UEGO or LSU sensor is not much compared to the range already provided by the single-cell AFR sensor that the 5VZ uses.

-Charlie