Replacing upstream O2 sensor, unsure if non-OEM Denso will prevent code

So i’m replacing my upstream sensor and i’ve heard a lot of talk on needing to get oem. I purchased a denso 234-9050 that is an exact fit, but it’s technically not the original part number. I’m wondering if the code will pop back on if I use the one you can get at autozone instead of oem.

 

Welcome to TW!

Don't buy autozone, They are overpriced crap.

Rockauto sells Denso. Why not get another Denso or two of the proper Denso's? I thought Denso was the OE Manufacturer.

What's the reason you're replacing your 02 sensors? What's the code?

 

I’m not purchasing at autozone I was just mentioning the part and that they sell it. Code is P0420 and my catalytic is still in good shape. I found the autozone denso on ebay for $75 instead of $200. I replaced with a cheap one first to see if it was the upstream and my check engine went off from that. Although i’ll probably do the downstream as well just to be safe. I was confused and thought I needed the exact original part number. People were talking about needing to splice the wires and what not so I wasn’t sure if I needed that or if i’m overthinking it. I got the original part number 89467-04010, but it says for manual transmission and mines an automatic. Will that matter? I just have a base cab 2wd and only have 2 sensors instead of 4 on my truck

 

Oh cool, I didn't know autozone sold the Denso 02 Sensors. I'd trust that one more than the ebay ones. Fake parts is a bigger problem these days than it's ever been.

There's a bunch of threads that are worth reading about this subject.

https://www.tacomaworld.com/threads/bad-o2-sensor.818277/

If your light is off, I wouldn't jinx it. If the code comes back then you could change the other. Good Luck!

 

Thanks for the help man. I’ll do downstream and maybe the PCV valve you mentioned in the thread next and hopefully that will fix the issue.

 

Have you tested for exhaust leaks?

 

My mechanic said exhaust looks good

 

Looks good or tests good?

 

I think after I do the downstream i’ll have him fully test the exhaust. My check engine came back on so i’m still not sure what the issue is.

 

I don't want to be that guy but, usually a P0420 code is one of the few you can usually safely just throw the part at.

The catalytic converter could and probably is actually defective. The easy way to check if you have a code reader that does live stream is to monitor the downstream sensor(s). It should be stable and relatively flat, if it's fluctuating like a sine wave then the catalytic converter is ready to be sold for metal recycling.

If you don't have a fancy scan tool then you can also check them with an infrared thermometer. On a good working converter, the outlet (tail-pipe) side should be hotter than the inlet (engine) side. This code is not a sensor fault, it's trying to say the catalytic converter is not doing it's job.

***important note, if you have oil/coolant burning issues or misfiring problems you need to fix those first or burning those things will ruin your new catalytic converter***

 

I don’t have any symptoms that my catalytic is failing, but I definitely haven’t ruled it out. My old 02 sensor was pretty blackened and looked worn out, so i’m covering all of my bases before I do the catalytic fix. I will have him check it though for sure. I heard p0420 could be 02 sensors as well so i’m doing the cheaper fixes first.

 

If you don't have any noticeable performance issues then as a diag/crutch because cat's are expensive you could try running a fouler. I don't know what year the obd was updated to not work with foulers but it's cheaper than sensors and a cat

 

I just had my cats replaced after a P0420 code (just last week before Thanksgiving). I swapped the two downstream O2 sensors from side to side to see if the code would follow the O2 sensor, but that just proved it wasn't the sensor.

Also, the upstream sensor is not an O2 sensor. It is an A/F sensor.

 

Thank you all for your replies. I’ll update as soon as I know. I hope it isn’t the cat, but it could be. I’ll mention the fouler to my mechanic.

 

Upstream is wide band, so it doesn’t bounce around like the traditional O2 sensors. It is a pretty steady reading.

 

Ops, my bad. Thank you for catching me.
I'll edit my post to avoid confusion

 

So....I went down this rabbit hole myself.

When my O2 sensors were bad I got a PO138 code which is an oxygen sensor code.

My understanding of the P0420 code is the ECU runs through a sequence where it verifies the O2 sensor readings are making sense to it, then it compares the reading from the WB sensor up front and the downstream sensor in back over a period of time while varying the A/F ratio. By doing this, the ECU can determine if the Cats are doing their job. If the answer is "NO", the code gets set.

Point being...on my truck it wouldn't set a P0420 code because the ECU checks the O2 sensors first. Once it determined the sensors are FUBAR it doesn't go any further to determine if the cats are working properly.

So...on mine....after replacing both O2 sensors, the PO138 code went away for good. 12 miles later, the P0420 code set because the ECU was able to check the cat system and it wasn't up to snuff.

What I did at that point was too get on toyota's site and check for recalls on my VIN that had never been completed. I found that one related to the catalytic convertors had never been done. I was able to set up an appointment at the dealer and they replaced the entire cat assembly at no cost...even gave me a loaner (although it was a $hitty loaner) for the day it took to do the work.

I think that was about 3 grand of work at a dealer a couple of years ago using Toyota parts.

My backup plan was going to be to use the Walker replacement assembly, which is a fraction of the cost of Toyota OEM...but may or may not be legal in your jurisdiction.

Good luck!

 

I had a P0420. It was my catalytic converter. My valve cover/sparkplug hole gasket was allowing oil to slowly leak into cylinder 3 and 4...not enough to notice during an oil change, but enough so that over several years it finally ruined my cat.

Replaced the cat with a relatively cheap option (less than 500 at the time) and it's been fine for the last 5ish years