O2 and or A/F Sensor ??

[jeeper1]

Hey guys,
I'm kinda confused right now about the O2 sensor and A/F sensor for my truck.
I have a 99 SR5 V6 4wd and I need to replace the sensors. I took a peek underneath and saw only 1 cat. I live in CA so Im guessing I need to get the CA sensor, I only found 1 sensor which was in front of the cat. I cant seem to locate the other one.

My question is do I need 1 or 2 sensors? I've seen 2 everywhere online but I don't know where its located. Any help would be appreciated.

The 4runner was originally purchase in the Midwest, Chicago I believe.
I have these 2 part #'s
234-9002; A/F sensor
234-4153; O2 sensor

Do you know which part goes where, front or back?
Do you think I can get away with just the 1 sensor since it was not a CA emission truck?

Thanks guys!!!!

 

[Doc2012]

Just because you LIVE in cali DOES NOT mean you have a Cali truck.

If you have 1 cat, you need a O2 sensor.

 

[jeeper1]

Just because you LIVE in cali DOES NOT mean you have a Cali truck.

If you have 1 cat, you need a O2 sensor.

Thanks Doc,

So 234-4153 would work? Why would people recommend that I get both sensors? Would it be because they think its a CA truck?

I read somewhere that the CA trucks usually have 2 cats (post 99) and that's why they need both the sensors. Is that true?

 

[TheDurk]

1, All 3G 4Runners had 2 sensors. In '99, there was a 49-state that had 1 cat, and the Cali. model that had 2. The sensors are one before the cat or cats, and one after. So you better find that other sensor just to be sure we know what we are talking about.

2. You need to buy the correct sensor for how the truck was built, not where you live. Look at your emissions sticker under the hood, right under where it says ENGINE FAMILY in the top left corner (or post a pic).

If it says something like:... AF, TWC(2) HO2S.....it's a Cali'

If it says something like: ....TWC, HO2S(2)...it's a Federal/49-state.

If your can confirm Cali. or not and auto trans or not, we can nail down the part numbers. Why are you changing the sensors in the first place? Answer that and I'll suggest one sensor or two (again, you definitely HAVE two.)

 

[shootmymime]

read of my thread i posted a few days ago. http://www.toyota-4runner.org/3rd-gen-t4rs/159207-pending;-p1130-then-week-later-p0125.html

this should help you diagnose what vehicle you have.

mine and my sticker under the hood told me i have a cali model, so if your sticker does not look like mine, being the same on the top left, you most likely dont. and i would not recommend the 9002 sensor.

 

[Doc2012]

Here's a super easy way to tell.

Unplug the sensor AFTER the cat, and take it off the exhaust.

Unplug the sensor BEFORE the cat. See if the AFTER cat sensor plugs into the BEFRE cat sensor.

If it DOES, you have a federal, which is BOTH O2 sensors.

If it DOESN'T, you have a Cali truck, which is a A/F sensor.

 

[jeeper1]

Thanks guys,

I will check first thing in the am.

Durk: I will get the info so we can find the part #. Also, its an auto. Reason for the change is that I didn't pass smog on the Nit. Oxide levels and need to change the cat. So I thought might as well change the sensors while I'm at it.

Shoot: Thanks man, I will check out the read!

Thanks for the replies fellas!!! Much appreciated.

 

[jeeper1]

Durk: it says something like: ....TWC, HO2S(2)...

 

[shootmymime]

Durk: it says something like: ....TWC, HO2S(2)...

yeah, this picture. see it under the large toyota words. if your is like mine with the description he gave. its a cali model.

but form your description, im sure yours is not.

 

[TheDurk]

Thanks guys,

I will check first thing in the am.

Durk: I will get the info so we can find the part #. Also, its an auto. Reason for the change is that I didn't pass smog on the Nit. Oxide levels and need to change the cat. So I thought might as well change the sensors while I'm at it.

Shoot: Thanks man, I will check out the read!

Thanks for the replies fellas!!! Much appreciated.

Just be aware that the rear sensor has no effect on vehicle performance or emissions. If it is not throwing a code, there is no real reason to replace it.

Do you have to meet the 1999 49-state NOx standard or the Cali. NOx standard? Because if it's the latter, I am not sure that is possible, if the truck was born 49-state. Or, if it is 49-state and that is allowed, then maybe you got tested to the wrong standard. I don't know the rules on imports of 49-state vehicles into California, but I'm worried that changing the cat may not get you where you need to go. A 49-state with a new cat, or even 2 new Cali Cats, is not going to pass the Cali. NOx test. You'd need a new ECU and switch to an A/F sensor to get there and maybe other stuff. Plus, I'm pretty sure it's illegal to sell 49-state cats in California. I hope you have this figured out.

 

[jeeper1]

Shoot: Yup mine is not CA.
Durk: So is there a possibility the technician that smogged my truck did it incorrectly? What should I do? Should I take it back to the smog shop and let them know what we just found out? Is there an entity that I can contact in regards to this matter besides the DMV? Really lost now... If I cant get a 49-state cat into CA, then will a CA cat work in this vehicle? In need of some direction. Thanks guys!

 

[jeeper1]

Also, prior to the smog test failure the CEL threw the code for "bank 1 too lean". You guys think that could be the culprit for the smog fail? It threw it a few times and I just cleared the code with the scan gauge. So when I took it to smog, the CEL was NOT on. What do you guys think? Thanks!

 

[TheDurk]

Shoot: Yup mine is not CA.
Durk: So is there a possibility the technician that smogged my truck did it incorrectly? What should I do? Should I take it back to the smog shop and let them know what we just found out? Is there an entity that I can contact in regards to this matter besides the DMV? Really lost now... If I cant get a 49-state cat into CA, then will a CA cat work in this vehicle? In need of some direction. Thanks guys!

I don't know the answers to any of those questions. I own a Cali.so I know how they work but I don't live there so I don't know the Cali. rules. I don't know if they even can test to Federal standards the way shops here in NJ and everywhere else can. Hopefully some of our CA brethren on here do. Just changing the cats to the Cali. two-cat system will improve things, but I don't know if it will pass the Cali. test. The true Cali's have the wideband air/fuel sensors (which requires a different ECU) for more precise fuel burning and thus have lower emissions. This may be needed to pass the test, I don't know.

Were you planning on having a shop change the cats? I'd talk to them and see what they were planning to do and if they understand the issues.