Please avoid quoting me in the future. Thank you.
O2 Sensor Fluctuating in Park and High Trans Temps
- Thread starter prybar
- Start date
Please avoid quoting me in the future. Thank you.
Robb235
Senior Member
Sorry, didn’t get notification of any replies in this thread.
This isn’t right. He has a front AFR sensor, which is not a narrowband O2 sensor that you’re describing. The AFR sensor is essentially a wideband O2 sensor. So as long as the AFR is constant, the output voltage reported by the ECU for bank 1 sensor 1 will also hold constant.
[MENTION=442099]prybar[/MENTION] you need to rescale the graph so that minimum value is 0.40v and max is 0.80v. Stoich (14.7 for pure gas) will return a voltage value of 0.66v. If you know how to setup custom PIDs in that app, you can actually program it to interpolate voltage into actual AFR value, or lambda value if you prefer that instead.
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It's not a wideband sensor. Voltage will fluctuate for the upstream sensor as it changes and adjusts fuel trims. Feel free to provide a source for where it says that it's a wideband sensor though.
phattyduck
Elite Member
Dual cats = front sensor is wideband (well, not quite - it is an AFR sensor with a reduced range compared to true wideband sensors). They are on '99-'00 California emissions and all '01-'02 4Runners. The output of that sensor is scaled to narroband-style readings for reporting via OBD-II, but can be converted back to wideband with the chart above.
All '96-'98 and Federal Emissions '99-'00 had a normal front O2 sensor that will have the widely varying output voltage.
Check the FSM, wiring diagrams, etc. It is all spelled out there.
-Charlie
Robb235
Senior Member
Toyota's Air Fuel Ratio sensor is absolutely a wideband O2 sensor. This is common knowledge on this board, or at least it was 10 years ago. Perhaps with a lot of the knowledge base moving on to newer vehicles, this has been forgotten. This is easily Google-able. In the earlier 3rd gens ('96-'98), the front O2 sensor was the traditional narrowband type O2 sensor. The 3rd gens that use the narrowband front O2 sensor can be readily identified by the fact that they have one (1) OEM catalytic converter. The B1S1 O2 readings on those sensors will oscillate between "high" and "low" and the narrowband O2 sensor does not have the ability to tell exactly what the air-fuel ratio is; only that is either rich or lean.
I believe it was in '99 (going from memory here) that the 3rd gens came with either the Federal Emissions or the California Emissions. Again, Federal Emissions used the traditional narrowband O2 sensor that should oscillate. The California Emissions used Toyota's "Air Fuel Ratio Sensor" that is essentially a wideband O2 sensor. The AFR sensor, unlike the traditional O2 sensor, can detect exactly what the air fuel ratio is at any given moment. The California Emissions vehicles can be identified by the fact they have two (2) OEM catalytic converters. The B1S1 O2 readings will be much more steady, and not bounce around like the older style narrowband O2 sensors. Instead, the reported voltage will correspond to the air-fuel ratio that I posted in the chart above.
At some point, I think it was either 2000 or 2001, all 3rd gens came with Air Fuel Ratio sensors, regardless of being Federal or California Emissions. Again, the fact that these 4Runners had two OEM catalytic converters readily identified them as having the Air Fuel Ratio sensors. Basically any 3rd gen that came from the factory with two catalytic converters has the Air Fuel Ratio sensor up front.
If it came from the factory with one OEM catalytic converter, then it has the older style narrowband O2 sensor up front. If it came from the factory with two, then it has the Air Fuel Ratio sensor up front.
In short, his scan tool did not switch the voltages between B1S1 and B1S2 O2 sensors. His scan tool is reading about what would be expected.
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Still waiting on any sort of evidence to prove that it's a wideband. As far as I've seen and experienced it's just a normal range air/fuel sensor (for California emissions) or a normal oxygen sensor for everything else.
There's a difference in sensing range between a wide band air/fuel sensor and the air/fuel sensor that Toyota uses. If you aren't going to provide any sources to back up your statements then I'll see my way out.
phattyduck
Elite Member
Wow, way to be pedantic. It is a 'wide-band' in the sense that it is not a traditional O2 sensor. You guys are saying the same thing. Ok, so it doesn't sense 9:1 up to 20:1, it only is accurate from around 12:1 up to 18:1. The point is that it can accurately sense more than about 14.6:1 to 14.8:1.
-Charlie
When presented with a conflicting point of view/idea from what I've established through my own experience, research, and knowledge to be true then I require substantiated evidence to change that. A lengthy explanation of what someone thinks is great, but not really a verified source. Maybe if more people adopted this outlook there would be fewer people believing the moon landing was fake, the earth is flat, and aliens walk among us. Am I being difficult? Absolutely! If the roles were reversed I would provide outside evidence as well if someone required it. Should be pretty easy for him to provide it since it's "easily Google-able".
EDIT: Yes, I know I'm a dick/*******/etc.
Robb235
Senior Member
LOL are you serious? So now you're acknowledging that it's an AFR sensor (and can report the actual air fuel ratio, unlike an older style O2 sensor)...
...which contradicts your prior post where you describe the operation of a traditional narrowband O2 sensor (and not an air/fuel sensor)...
So let me ask you this. Do you still stand by your statement that you think OP's scan tool is switching readings between sensor 1 and 2?
Robb235
Senior Member
[MENTION=319302]Bad Luck[/MENTION], here you go. Here is some reading material for you:
https://www.autoequipment.com.au/image/data/Support/Toyota Planar Sensors - Part 3.pdf
Wideband O2 Sensors and Air/Fuel (A/F) Sensors
https://www.autoequipment.com.au/image/data/Support/Toyota Planar Sensors - Part 3.pdf
Wideband O2 Sensors and Air/Fuel (A/F) Sensors
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/...ensor measures,range of a conventional engine!) where as the Toyota sensors go from 12.5:1-18.5:1 (https://www.autoequipment.com.au/image/data/Support/Toyota Planar Sensors - Part 3.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/...ensor measures,range of a conventional engine!
Robb235
Senior Member
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.
Robb235
Senior Member
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.
Robb235
Senior Member
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?
Robb235
Senior Member
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.
