Which O2 sensor?

[Tatonka]

I want to buy a replacement 02 sensor for my 99. Apparently which part I buy depends on whether I have a Federal or California emissions system. From what I have read looking at the system and counting sensors to determine which I have does not really work. The sticker under the hood is supposed to tell me one way or the other... but look at mine - it says both! FED at the bottom but California in the text in the middle . So wth do I have?!?

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[LittleCaesar]

You can check the door jamb but a quicker way is to look under the 4runner. Two cats are for California, one kitty for the other 49 states.

 

[TheDurk]

That's a federal. No doubt. The verbiage is confusing--ignore it. The line that counts is: SFI, HO2S(2), TWC.

if it were a Cali, it would say: SFI, A/FS, TWC(2), HO2S or similar. Years vary slightly.

HO2S is heated oxyen sensor, TWC is three way converter, A/FS is air/fuel sensor.

So yours has two standard O2 sensors and a single cat, i.e Federal system.

 

[Tatonka]

That's a federal. No doubt. The verbiage is confusing--ignore it. The line that counts is: SFI, HO2S(2), TWC.



if it were a Cali, it would say: SFI, A/FS, TWC(2), HO2S or similar. Years vary slightly.



HO2S is heated oxyen sensor, TWC is three way converter, A/FS is air/fuel sensor.



So yours has two standard O2 sensors and a single cat, i.e Federal system.

Great info - thanks!


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