Have you guys replaced an original o2 and found that it didn't perfectly match the new one?

3 weeks ago, I put in a replacement downstream Denso 234-4153 and a replacement upstream 234-9003. I crosschecked these part numbers with Auto Zone, NAPA, Advance Auto and URD.

My truck is a 1999 4wd manual w/ Cali emissions. It has the CARB sticker under the hood and dual cats which I have never suspected of being bad.

The 234-4153 does not match the sensor that I pulled out. The one I removed had a Toyota logo on it.

These pictures show the difference. I threw the old one in the trash at my parents'. My dad will get back to me soon with whatever kind of info on the old sensor that he can read from it.
20150103_123440 by samwisemason, on Flickr
20150103_123344 by samwisemason, on Flickr
20150103_123332 by samwisemason, on Flickr

Within 50 miles after install, the CEL came on, another p0420. I cleared it, and it came back within another 50 miles.

So I either have
1--the wrong sensor for a '99 4wd Cali manual
or
2--one or two of the cats went bad at the instant I changed the sensors. I just passed NH emissions in June.

But why else would this downstream sensor not match? I'm 99% confident it's original.

Has anyone else had a similar issue with mismatched sensors?

I too am getting the same code, dealer said my cats were bad.. Along with a crazy quote to repair. Curious to hear your results

Reviving an old thread because I am having similar issue. Used Rock Auto and Denso website to get the part number 234-4153 for downstream sensor. I'm assuming that means the one after the cat. pulled old one out and they are different. new one will not fit. Might fit if i force it, but don't want to do that. Anyone have suggestions? 99 auto 4x4 cali emissions

What motor?

3.4 v6

Try putting your old downstream sensor back in and see if it goes away, since the down stream only monitors the cats it’s not as important as the air fuel ratio sensor

Following, and I'm no help to you except to say a lot of reports of counterfeit parts out there right now. Faking expensive replacement parts are perfect for scammers preying on our limited budgets. Hopefully not the case.

Where did you buy? It's mostly been reported on amazon and ebay purchases. Spark plugs being the one I saw most recently.

I did get it off amazon. used the part numbers from Denso website and Rock Auto

I have reset the check engine light like 10 times. it always comes back. Not sure if you know anything about diagnosing.. I used the torque app connected to the OBD2 and monitored the voltages of both o2 sensors. Per this fourm (cant remember who posted) One voltage should fluctuate while the other stays constant. if they both fluctuate then it is the cat. on mine bank 2 was changing alot and bank 1 sensor was pretty constant. always .6-.7 v So I figured it was a good bet to try the cheapest fix first.

I would probably send it back to amazon for a refund, a genuine oem sensor would definitely fit, then go get one from rock auto since they aren’t going to be selling Chinese knockoffs

Explain whay won't fit. The sensor won't fit in the bung, the studs won't go in the flange, or the plug isn't right?

With Cali. emissions, the wideband air/fuel gets a constant voltage and what varies is the current. So you can't compare the two.

If you look at the picture the new one has a lip. that is to wide... other than that everything matches up. I'm going to get under there again and maybe I just have to tighten down the nuts and force it in.

Can you post a picture of the sensor that doesn’t fit?

Is it flanged using a flat metal gasket and two bolts or studs with nuts or is it a screw in sensor?


Sent from my iPhone using Tapatalk

if you look at the pic from the original post it is exactly the same.

So I’m an idiot. It fits but it’s really snug. I was worried about ruining it but the force of the bolts gets it set proper.