So, the check engine light comes on today. So, I drive my 97 3.4L with 215K miles over to advanced auto to get it scanned.
It comes back as O2 sensor number 1...or bank 1, something like that.


Now, three years ago, this exact same thing happened to me. And after buying the new O2 sensor I crawled under the truck only to find more than one

So I did what any self respecting mechanic would do...I guessed. Apparently I guessed right, cause it fixed the problem.
I dont remember which O2 sensor the scanguage said 3 yrs ago...

Anywho, how many O2 sensors are there and how do I identify which one is "number 1"?

Thanks for any help

matt

 

Our trucks have two: Bank 1 Sensor 1 before the cat and Bank 1 Sensor 2 after the cat. There is no Bank 2 because that only exists on cars with dual exhausts.

 

phenomenal.
thanks so much.

I know the wife wanted to shoot down to disney this weekend, so I'll try and bang it out beforehand...just in case running with a bad one has any chance of causing bigger problems

thx again

 

I have a 1995 4runner with a 98 3.4 in it. Besides the CEL, what are the symptoms of a bad o2 sensor? The CEL light came and the codes indicated the upstream sensor (does not have a downstream sensor). My truck recently started having trouble making it past 45mph. It just kind of quits accelerating and all my power disappears, like I can't load the engine very much. Would an o2 sensor cause these symptoms?

 

that sounds like a plugged up cat converter. how long have you been driving since the CEL came on?

 

I bought it about a week and a half ago. The CEL came on the next day but I expected it because of the missing downstream sensor. I hit a decent sized puddle yesterday and it has been acting screwy ever since. I limped it to autozone to get the codes read and it showed the upstream sensor. Since I have been driving it with the CEL light on for over a week, I am not sure when the upstream sensor tripped. I unhooked my cat converter at the forward flange and gave it a good 3/8" gap and it still drives like a dog.

 

It will start and idle like usual. I can even rev it up, but as soon as I put any decent load on the engine it just kind of fades out and will eventually start to jerk like a rookie on the clutch.

 

Mine did that when the wire harness at the ecu got wet.

 

Yeah, mine must have dried out because it's running fine now. I think mine was the o2 sensor getting wet because it was wired (by previous owner) across bottom of tranny. I think I have some wire re-routing and sealing in my future!

 

Thanks for everyone's help! :-)

 

My 02 2.7 has the same deal, but not sure which one to change, have to double check the codes. My 89 4 runner had the same deal. jumped and bucked horribly, $75 o2 sensor and 30 minutes and it ran like a top..