# 2000 Avalon, Air/Fuel ratio sensor DTC



## Brainbucket (Mar 30, 2015)

O2s have heaters built into them to get them working faster on cold start up. The O2s are working but the heaters are not. Yours are faulty and needs to be replaced.:vs_cool:


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## ukrkoz (Dec 31, 2010)

Big, at this point, you may want to jump ships and go to toyotanation for Avalon related questions.


Hey, took care of this for you. I'll keep you posted.


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## Bigplanz (Apr 10, 2009)

Brainbucket said:


> O2s have heaters built into them to get them working faster on cold start up. The O2s are working but the heaters are not. Yours are faulty and needs to be replaced.:vs_cool:


What is confusing to me is why all the readings are normal. The heater circuit has to work for the sensor to work, so I will replace them at some point. What does the car do to calculate fuel trim without the two front bank sensors working? Car runs great, and gas milage is 16.2 MPG for 100 miles of stop and go driving this weekend.

I assume the car is using default numbers to calculate fuel trim.


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## Bigplanz (Apr 10, 2009)

ukrkoz said:


> Big, at this point, you may want to jump ships and go to toyotanation for Avalon related questions.
> 
> 
> Hey, took care of this for you. I'll keep you posted.


I went over there to the Avalon 2 gen forum and loked around. I saw you were a moderator. I will go over there and sign up.


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## Brainbucket (Mar 30, 2015)

Bigplanz said:


> What is confusing to me is why all the readings are normal. The heater circuit has to work for the sensor to work, so I will replace them at some point. What does the car do to calculate fuel trim without the two front bank sensors working? Car runs great, and gas milage is 16.2 MPG for 100 miles of stop and go driving this weekend.
> 
> I assume the car is using default numbers to calculate fuel trim.



The heaters work on cold startup to get the O2 to operating temp quicker. After engine starts to heat up, O2 don't need the heaters. I believe O2s need to get up to 600 degrees before they start to work efficiently, but now I'm taxing my memory. The O2s are working. They are not working as quick as the heaters are not getting them up to operating temps quickly on cold start.:vs_cool:


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## Bigplanz (Apr 10, 2009)

Brainbucket said:


> The heaters work on cold startup to get the O2 to operating temp quicker. After engine starts to heat up, O2 don't need the heaters. I believe O2s need to get up to 600 degrees before they start to work efficiently, but now I'm taxing my memory. The O2s are working. They are not working as quick as the heaters are not getting them up to operating temps quickly on cold start.:vs_cool:


From what I have read, A/F sensors have a heater circuit that generates at least 1200 degrees to be effective. If the heater circuit on an A/F sensor fails, it will never work. An O2 sensor will just heat up slower, but will work when it reaches 600 degrees.


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## ukrkoz (Dec 31, 2010)

I don't think you have A/F sensor for the year. Likely g'ol O2 sensors.


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## ukrkoz (Dec 31, 2010)

Bigplanz said:


> I went over there to the Avalon 2 gen forum and loked around. I saw you were a moderator. I will go over there and sign up.



Yep. I'll make you deputy. :vs_cool:


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## Bigplanz (Apr 10, 2009)

ukrkoz said:


> https://www.youtube.com/watch?v=fBQ-1pqSoXM
> 
> 
> I don't think you have A/F sensor for the year. Likely g'ol O2 sensors.


From all the service info I have found, the 2000 Avalon has an Air/Fuel Ratio sensor on each exhaust manifold, and one standard O2 sensor behind the cat. 

I went to PullaPart to try removing one. Wanted to find out how difficult it was to remove. Actually, it came right off, with N off-set O2 socket. It was harder her the electtrical connector off than remove the sensor. Here is a sensor I pulled from a salvage 2000 Avalon. Unfortunately, the heater circuit shows open circuit, so it's bad too. You can see the part number in the picture. None of the ones I tested were any good. A Denso sensor is around $117, new.


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## ukrkoz (Dec 31, 2010)

Fancy.


BTW, though it's too late, same year Camry 4 cyl is considered a tank. Literally indestructible and refusing to die/break down.


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## Brainbucket (Mar 30, 2015)

Rock Auto are around $25.00:vs_cool:


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## Bigplanz (Apr 10, 2009)

Brainbucket said:


> Rock Auto are around $25.00:vs_cool:


The ones I need are upstream sensors. Denso is $111.

https://www.rockauto.com/en/catalog...22,exhaust+&+emission,oxygen+(o2)+sensor,5132


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## Brainbucket (Mar 30, 2015)

Bigplanz said:


> The ones I need are upstream sensors. Denso is $111.
> 
> https://www.rockauto.com/en/catalog...22,exhaust+&+emission,oxygen+(o2)+sensor,5132


I looked up for a Honda. Opps


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## ukrkoz (Dec 31, 2010)

https://www.ebay.com/p/4011630104


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## Bigplanz (Apr 10, 2009)

ukrkoz said:


> https://www.ebay.com/p/4011630104


Thanks for the link! That's a great price. I read/heard "don't cheap out on Toyouta sensors, Go with Denso." I only want to change these sensors ONCE, not multiple times.

Hardest thing is getting the blankety blank connector off. It is like they are super glued on. I squirted some silicone spray on one at the junkyard, and that helped, but, damn! 20 seconds to unscrew the sensor and half an hour leaning over the engine trying to get the connector off.


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## ukrkoz (Dec 31, 2010)

Yep. Got to get it pressed just right - and it's different per each manufacturer, aye, mate?
Like every Lexus we owned had iffing O2 sensor bank2 problem. I replaced them with aftermarkets and never had any issue. Same goes for ignition coils. That one on ebay even looks like one you pictured.


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