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Toyota AF oxygen sensor ohms

  • babajis2010
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03 Jun 2019 17:57 - 03 Jun 2019 18:18 #30348 by babajis2010
Toyota AF oxygen sensor ohms was created by babajis2010
Hello experts in the house my name is David and I’m from Sweden.
I would like to know how to specifically check the AF oxygen sensor ohms reading for my car. It thus appear Toyota has one part number for different ohms readings.
My car throws up P0420 and P0430 and I have done and change all parts and now I give up.
I finally stumbled on the repair manual for Toyota Avensis Verso 2001-2007 that states 1.8 - 3.4ohms at 20degrees, but I’m suspecting the 1.8-3.4ohms may be for 2004 models above.
Toyota dealership used my REG NO to order for brand new OEM AF sensors that both read 1.1ohms at 20degrees Celsius.
I am taking this case up with the dealership and I need you guys to point me in the right direction because the sensors don’t come cheap.

Toyota gave me new OEM upstream sensors that read 1.2ohms each at 20degrees Celsius, and the problem persist.
They have printed a service bulletin on how to address the problem which I’m attaching. Under description of phenomenon bullet point 3, it says (no influence on driveability or engine performance), but I am experiencing driveability, poor engine performance and loss of power (pls note the engine idles fine, no stalling, everything looks fine with the engine except that the car doesn’t move as it should on the highway and if I force it by driving over 120km, the CAT becomes hot and makes this frying sound when I park) Is it safe to conclude that the recommendation by Toyota to change ECU and CAT does not apply in my case since I have engine loss of power.

The tech doc ID for my car is 16026 if anyone can help me check the ohms of A/F sensor this car should use.
>>When I used OBD WiFi to check Bank1Sensor2 and Bank 2 sensor2, the waveform was steady at 0.7v to 0.9v but dropped when the fan kicked in and when I rev the engine. Are these the downstream sensors? The waveform and voltage drop only happens when the fan kicks in or when I rev the engine. I will try to use the OBD WiFi to get screenshots for waveform of Bank1Sensor1 and Bank2Sensor1
>>When I used techstream, the voltage dropped down from 3.29v for Bank1Sensor1 and Bank2Sensor1 upstream sensors...see attached pix. I don’t have an oscilloscope to graph a waveform as shown I the service bulletin, but using the techstream the voltage drop of the upstream sensors signify a rich condition.

Verso is not listed as needing a ECU software upgrade, only previa and RAV4. The dealership wants me to replace ECU and CAT which I do not believe.

How do I fix this rich condition without being a part changer.
I would really appreciate you guys help.
Last edit: 03 Jun 2019 18:18 by babajis2010.

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  • babajis2010
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03 Jun 2019 17:58 #30349 by babajis2010
Replied by babajis2010 on topic Toyota AF oxygen sensor ohms
More attachments of waveform and service bulletin
Attachments:

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  • Chad
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03 Jun 2019 20:18 - 03 Jun 2019 20:20 #30354 by Chad
Replied by Chad on topic Toyota AF oxygen sensor ohms

babajis2010 wrote: but I am experiencing driveability, poor engine performance and loss of power (pls note the engine idles fine, no stalling, everything looks fine with the engine except that the car doesn’t move as it should on the highway


I think you need to worry about you Cat, more than your O2 sensors. You are describing the classic symptoms of a restricted exhaust.

and if I force it by driving over 120km, the CAT becomes hot and makes this frying sound when I park)


:woohoo: This is, definitely, not normal.

I would Is it safe to conclude that the recommendation by Toyota to change ECU and CAT does not apply in my case since I have engine loss of power.


Not, necessarily. I'm not ready to call an ECU, yet. But, it certainly doesn't sound good for the CAT.

P0420 and P0430 are efficiency codes. Basically, the CAT is not absorbing oxygen. The exhaust that enters the CAT is the same as the exhaust exiting the CAT. This is a condition that, generally, requires a new CAT. However, this will not cause a drivability issue.

But,

and if I force it by driving over 120km, the CAT becomes hot and makes this frying sound when I park)

I think it might be safe to say the CAT has melted down, and you have exhaust restriction. THIS will cause a drivability problem and require a new CAT, too. If you can, remove the UPSTREAM O² sensor and install a pressure gauge. A back pressure of more than 2 psi, at 2000 RPM is a concern. More than 3 psi is a problem.

"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."
Last edit: 03 Jun 2019 20:20 by Chad.

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05 Jun 2019 15:15 #30417 by chief eaglebear
Replied by chief eaglebear on topic Toyota AF oxygen sensor ohms
hi sir still trying to figure out af diagnostics myself andy fcfaden who is a moderator on here is really good with af diagnostics and will probably ask you to move this to repair section you will get more hits I do know that instead of interpreting voltage an AF sensor will measure current and on some models only the upstream sensors are wideband

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08 Jun 2019 22:19 #30539 by Tutti57
Replied by Tutti57 on topic Toyota AF oxygen sensor ohms
Tyler wrote up a nice sticky post on AF sensor testing in the diagnostic tools and techniques section of the forum.

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