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Hello evreyone did anyone have graph of how o2 sensor 2 must work? From the start when i turn ignition on techstream shows me 0.250V then when i start engine it goes to 0.000 in 15sec sometime it shows 0.005V. STFT goes to 19.5% and LTFT 52%
Thx for help.
You've had an issue with the Upstream Sensors in this thread, where did that go afterwards, are they new now?
If the A/F Sensors are new, what Brand are they?
Any Sensor 2 sensors are referred to as Downstream Sensors, they are not the ones setting your Mixture, they are there only to monitor the Health of the Catalytic Converters in a car for the Environment Regulations, it's their Only function. Bank 1 Sensor 2 that you are checking is not what you need to look at for the Fuel Trim issues you have.
What you should check is the readouts from Bank 1 Sensor 1 and Bank 2 Sensor 1 sensors, as they are the ones responsible for a correct mixture, they are referred to as Upstream Sensors. In your particular car, they work using a different principle, hence the readouts will be different as well, instead of Sinusoidal Wave, you will see a more or less linear graph that should sit at about 3.2V when at the right mixture, without any dips or other fluctuations.
Corrections at 52% is a LOT, it goes beyond the limits for Corrections that the ECU should be capable of making, usually that's a result of one of the sensors sending utterly incorrect information, or being disconnected entirely. Get the Readouts for both Upstream Sensors (B1S1 and B2S1), as well as MAF Sensor, make sure that their Values are consistent and within spec, if one of the sensors would show values that are completely out of spec, try disconnecting said sensor and see what changes.
To answer your question though, Bank 1 Sensor 2 is supposed to have a nearly straight graph, sitting at about 0.5V, that is if your Catalysts are in perfect shape, or oscillate with the amplitude dependent on the condition of your Catalyst, the worse they perform, the higher the amplitude will be, below is a graph of what it's supposed to look like. The readings you have usually indicate a fried sensor, you will need to replace it at some point, though it does not affect neither driveability nor your main issue.
You've had an issue with the Upstream Sensors in this thread, where did that go afterwards, are they new now?
If the A/F Sensors are new, what Brand are they?
I bought 2 new A/F sensors and replace them, drive couple days, nothink changes so i returned them. It was toyota A/F sensors with part numbers that u help find me in previous thread.
Originally Posted by Arsenii
Any Sensor 2 sensors are referred to as Downstream Sensors, they are not the ones setting your Mixture, they are there only to monitor the Health of the Catalytic Converters in a car for the Environment Regulations, it's their Only function. Bank 1 Sensor 2 that you are checking is not what you need to look at for the Fuel Trim issues you have.
I thought like you but i find one interesting video:
What you should check is the readouts from Bank 1 Sensor 1 and Bank 2 Sensor 1 sensors, as they are the ones responsible for a correct mixture, they are referred to as Upstream Sensors. In your particular car, they work using a different principle, hence the readouts will be different as well, instead of Sinusoidal Wave, you will see a more or less linear graph that should sit at about 3.2V when at the right mixture, without any dips or other fluctuations.
I checked b1,2 s1 voltages they goes from 3.1 to 3.5, maf at idle 3.4g/s at 2500 its 12.5, i did every active test in techstream software, everithink work good. No missfire till corrections goes wild. No vacuum leakage at all. Compression 12bar in every cylinder. I change repair kit of injectors (include filters of injectors). New fuel filter. New fuel pump from camry 30 v6 (dunno mb i will change him back because not sure about his productivity). Changed every gaskets in exhaust system.
Originally Posted by Arsenii
Corrections at 52% is a LOT, it goes beyond the limits for Corrections that the ECU should be capable of making, usually that's a result of one of the sensors sending utterly incorrect information, or being disconnected entirely. Get the Readouts for both Upstream Sensors (B1S1 and B2S1), as well as MAF Sensor, make sure that their Values are consistent and within spec, if one of the sensors would show values that are completely out of spec, try disconnecting said sensor and see what changes.
To answer your question though, Bank 1 Sensor 2 is supposed to have a nearly straight graph, sitting at about 0.5V, that is if your Catalysts are in perfect shape, or oscillate with the amplitude dependent on the condition of your Catalyst, the worse they perform, the higher the amplitude will be, below is a graph of what it's supposed to look like. The readings you have usually indicate a fried sensor, you will need to replace it at some point, though it does not affect neither driveability nor your main issue.
Hope this helps and best of luck!
This happens when i pull off whole exhaust system and uscrewed sensor2 so i wana check mb replacing will help.
It was toyota A/F sensors with part numbers that u help find me in previous thread.
How sure are you that those were OEM sensors? To be perfectly honest, even here I would trust them to be OEM only if I got them either Directly from a local Toyota Dealer, with a package physically handed to me over the counter, or a small set of reputable locations listed in your previous thread, I would not trust any other sensor to be OEM, hence why I mentioned that Denso may be a better option in your case, not to mention the gaping price difference between OEM and Denso.
Originally Posted by SmileUxA
I thought like you but i find one interesting video:
Thaat's weird..
Just ran a similar experiment in my 2000 ES300 by disconnecting the Downstream (Sensor 2) sensor completely, the connector for which is located under the Driver's seat, not a fun exercise if you were wondering, but anyway. The engine was fully warm, no Fault Codes stored in the system, I ran the test before a CEL had a chance to trigger, meaning that the car was still relying on the sensor output, which was dead at 0V the entire time, as a result, I didn't observe any change in Engine Performance in general, or Fuel Trims in particular, attached pictures of the Engine Live Data. I then reconnected the Downstream sensor without shutting the engine off and immediately got its Output back, even though my Catalysts are way past their heyday, there was, again, no change in the Engine Performance.
The thing is that in the Video linked earlier, they supplied more than 1.2V to a sensor that is only supposed to output close to 0.5V in its Steady State, what they essentially did is flipped the table per say, going from the Lowest possible output, which caused an extremely Lean condition, to the Highest Possible output, and the car worked perfectly with it instead of considering the new readings to be an extremely Rich mixture as logic would suggest, and adjusting accordingly.
What I am saying is that if it was the precise Value fed to the ECU from the Downstream Sensor that caused their issue, if 0V caused Lean condition, then 1.2V absolutely must cause Rich condition, but instead the car ran perfectly, even though the readings were extremely off the mark. That makes me wonder if it was not the specific Number that the sensor outputted that caused the problem in the video, it was the presence of Voltage as a whole that made it happen.
Either way, B1S2 is probably not the primary item on the list of concerns, with that, seeing the readouts that you get out of it, might as well replace it now, as it will have to be done at some point, depends on whether you can source one from a reputable place.
Originally Posted by SmileUxA
I checked b1,2 s1 voltages they goes from 3.1 to 3.5
That's quite a bit of variation. Referring to the same video, look a the A/F sensor values during the A/F Ratio Active Test, they only go from 2.8V at the absolute Lowest to 3.4V at absolute Highest, those are very sensible to changes. Values you are getting may be enough to cause the issue you have, coming back to the faulty A/F Sensors.
Originally Posted by SmileUxA
I change repair kit of injectors (include filters of injectors).
An Injector Repair Kit..? Well that's new..
Can you share any pictures or links to said repair kit? Those are more or less modern injectors, they don't seem to be repairable in any way, and even if they are, only with utmost care. Is there a chance you know of someone with an Injector Stand locally?
07-01-24, 11:50 AM
Graph of B1S2
