A/F - O2 sensor Help/Clarification

[xier17]

Hello All,
My name is Mike and I am new to posting, but have been a registered member over a year now and have been doing mods and routine maintenance on my 4runner using all the amazing information found on the forums Changing out the A/F and O2 sensors is next on my list, but I am confused on which sensor I am suppose to change. I called up Toyota and gave them my VIN, and they told me my 4runner uses an A/F sensor and two O2 sensors (Cali). Checking around the forums I've read that non-cali uses 2, O2 sensors, and cali vehicles use an A/F sensor and an O2 sensor..., but all the vehicles have and upstream, and a downstream, so why is mine different? Did i possibly hear them wrong? Where did this 3rd sensor come from? Or did the Toyota guy tell me something wrong?

Here are the part numbers I was given:
A/F Sensor - 89467 35011 (before or after Cata?)
Front - 89465 80034 (Before or after Cata?)
Rear - 89465 49105

Searching on the forums, Cali vehicles 'Upstream' sensor is the A/F sensor, and non Cali is just an O2 sensor, correct?

Using URD, I found what sensors my 4runner needs:
234-9002 Upstream - Amazon
234-4153 Downstream - Amazon

The Upstream sensor on amazon says its an A/F ratio sensor, so does that mean it is equivalent to 89467 35011? If that is the case then the other 2 im guessing are O2 sensors? When I search online and read post and look at images of the location of the sensors I only hear about and see 2 sensors. Why was i told that my 4runner uses 3?

-Cutout from Toyota FSM where you can see the sensors

-Copy of what Toyota sent me

I called another toyota location and I was told the I have and A/F, front, and Rear sensor, and that the rear, was a California emission sensor...I thought the rear sensor was the downstream, the one closest to the tailpipe. Did i confuse this? Is the 'Front' (Upstream) and 'Rear' (Downstream)?

Toyota told me any number starting with 89467 is an A/F ratio sensor. So in the end I am still unsure which of the sensors is the real A/F sensor i need to replace. and where it is located. Basically my goal is to replace a sensor to see if I can get better gas mileage. I read the sensor should be changed very 75k miles or so, and I am pretty sure the previous owner has never changed it. If anyone understands the attached diagrams and can explain and clarify it to me, I would greatly appreciate it. Thanks!

2000 4runner sr5 4wd E-locker

 

[symlink]

I just got done changing my a/f sensor on my 99 runner. If you have two cats then its the cali version and they only came with 2 sensers an upstream and a downstream. Your upstream is part # 234-9002 for the denso. Im not sure what the other one is part #wise but its just a regular o2 sensor. Word to the wise after spending 3 hours trying to get the nuts off the studs and this was after i soaked them down with pb blaster. I decided enough was enough after trying vice grips pipe
wrench etc etc. And bought a set of Irwin nut grippers and got them both off in less than 5 minutes. So id go that route if you plan to diy.

 

[4Reak Show]

Hello All,
My name is Mike and I am new to posting, but have been a registered member over a year now and have been doing mods and routine maintenance on my 4runner using all the amazing information found on the forums Changing out the A/F and O2 sensors is next on my list, but I am confused on which sensor I am suppose to change. I called up Toyota and gave them my VIN, and they told me my 4runner uses an A/F sensor and two O2 sensors (Cali). Checking around the forums I've read that non-cali uses 2, O2 sensors, and cali vehicles use an A/F sensor and an O2 sensor..., but all the vehicles have and upstream, and a downstream, so why is mine different? Did i possibly hear them wrong? Where did this 3rd sensor come from? Or did the Toyota guy tell me something wrong?

Here are the part numbers I was given:
A/F Sensor - 89467 35011 (before or after Cata?)
Front - 89465 80034 (Before or after Cata?)
Rear - 89465 49105

Searching on the forums, Cali vehicles 'Upstream' sensor is the A/F sensor, and non Cali is just an O2 sensor, correct?

Using URD, I found what sensors my 4runner needs:
234-9002 Upstream - Amazon
234-4153 Downstream - Amazon

The Upstream sensor on amazon says its an A/F ratio sensor, so does that mean it is equivalent to 89467 35011? If that is the case then the other 2 im guessing are O2 sensors? When I search online and read post and look at images of the location of the sensors I only hear about and see 2 sensors. Why was i told that my 4runner uses 3?

-Cutout from Toyota FSM where you can see the sensors

-Copy of what Toyota sent me

I called another toyota location and I was told the I have and A/F, front, and Rear sensor, and that the rear, was a California emission sensor...I thought the rear sensor was the downstream, the one closest to the tailpipe. Did i confuse this? Is the 'Front' (Upstream) and 'Rear' (Downstream)?

Toyota told me any number starting with 89467 is an A/F ratio sensor. So in the end I am still unsure which of the sensors is the real A/F sensor i need to replace. and where it is located. Basically my goal is to replace a sensor to see if I can get better gas mileage. I read the sensor should be changed very 75k miles or so, and I am pretty sure the previous owner has never changed it. If anyone understands the attached diagrams and can explain and clarify it to me, I would greatly appreciate it. Thanks!

2000 4runner sr5 4wd E-locker

Yeah I've never seen a 3rd gen with more than 2 total sensors. The easiest way to be absolutely certain is your emissions sticker under the hood. It will list all the emission devices installed and say stuff like: "EVAP, H02S (2), EGR, EFI..." And where it lists the 02's it either says "H02S (2)" ---meaning 2 02 sensors--- or "H02S, AFR" ---02sensor, Air/fuel ratio sensor---
Good luck

 

[TheDurk]

You have two sensors, period. Either your dealer is a dufus or you misunderstood. The A/F is upstream on Cali's. Use the numbers you got from URD to order a Denso sensor from Amazon. The A/F sensor is worth changing in your situation. You might as well wait on the rear until you get a code because it has no real impact on economy or performance.

 

[xier17]

Thank you everyone for the information and clarification. Now I know what to do.

 

[s20004runner]

I did it too recently and I agree w/ symlink more than 4reak. All labels and searches indicated that I should have the AFR/O2, but I didn't.

I did a lot of research and the absolutely certain is to see if you have one or two cats. My 99 t4r had one cat thus two O2 sensors.


If you have two small cats (AFR upstream and O2 downstream)

BTW, your O2/AFR nuts may be stripped, in that case use a locking vice grip.

good luck

 

[TheDurk]

I did it too recently and I agree w/ symlink more than 4reak. All labels and searches indicated that I should have the AFR/O2, but I didn't.

I did a lot of research and the absolutely certain is to see if you have one or two cats. My 99 t4r had one cat thus two O2 sensors.


If you have two small cats (AFR upstream and O2 downstream)

BTW, your O2/AFR nuts may be stripped, in that case use a locking vice grip.

good luck

The only way the label is wrong is if the hood is not original. As posted above, look in the top left corner:

A/F S, TWC(2), HO2S = Cali.
TWC, HO2S(2) = 49State/Federal.

Rely on this, the rest of the label can be very confusing.

 

[xier17]

Well I followed the info every has given me and I replaced my A/F ratio sensor....finally... It was a lot easier than I expected. Later on I put in Redline Fuel system Cleaner, and filled her up with 91 octane.

All of that was about 5 days ago, and now my check engine light came on and gave me a P0420 code. I have looked around on the forums, and have read up on how to take care of that code, so that is next on my list. Hopefully its just the rear 02 sensor.