The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread

What are Bank 1, Bank 2, etc.?
Since this question pops up from time-to-time, here's an easy to follow diagram that illustrates what they mean when your OBDII code scanner (or manual) tells you something like "O2 sensor, Bank 1, Sensor 2":

View attachment 12208


What does upstream and downstream mean?
Simple, upstream means the O2 sensor is "upstream" of the catalytic convertors, meaning before the catalytic convertors. Downstream means the O2 sensor is "downstream" of the catalytic convertors, meaning after the catalytic convertors.


What brand of O2 sensors should I use for replacements?
Pay close attention to this one so you can do it once and do it right! The Jeep Wrangler TJ is extremely sensitive to all oxygen sensors other than NGK / NTK. Bosch O2 sensors and all the others (including the crappy Chinese brands you'll buy at your local auto part store) are very well documented as not working properly with our TJs. In other words, you plug them in and you assume all is well, until you notice your check engine light isn't going away. This is almost always due to the fact that you didn't use an NGK / NTK replacement O2 sensor.


Okay, so why don't other sensors (i.e. Bosch) work on our Jeeps?
Glad you asked! Check out this video for a detailed explanation of why other brands of O2 sensors don't work on our TJs:



So which O2 sensors do I need?
I'm going to break down which sensors you need based off what year your TJ is. The part numbers (and information) below were taken directly from the NGK website, so you can assure it is 100% accurate (even double checked each individual year and model before writing this thread).

Be aware that NTK O2 sensors are identical to NGK and they share the same part numbers. NTK is more common so it will usually be easier to find. Use the same part numbers for NTK as shown below.


4 Cylinder Engines
1997-2000
NGK #23506 - Bank 1, Sensor 1 (Upstream)​
NGK #23151 - Bank 1, Sensor 1 (Upstream) (1998 ONLY)​
NGK #23099 - Bank 1, Sensor 2 (Downstream)​
2001-2004
NGK #23138 - Bank 1, Sensor 1 (Upstream)​
NGK #23141 - Bank 1, Sensor 2 (Downstream)​
2005-2006
NGK #23159 - Bank 1, Sensor 1 (Upstream)​
NGK #23159 - Bank 1, Sensor 2 (Downstream)​
6 Cylinder Engines
1997-1999
NGK #23151 - Bank 1, Sensor 1 (Upstream)​
NGK #23099 - Bank 1, Sensor 2 (Downstream)​

2000 Federal Emissions (Non-Export)
NGK #23122 - Bank 1 Sensor 1 (Upstream)​
NGK #23099 - Bank 1 Sensor 2 (Downstream)​

2000
NGK #23122 - Bank 1, Sensor 1 (Upstream)​
NGK #23506 - Bank 2, Sensor 1 (Upstream)​
NGK #23099 - Bank 1, Sensor 2 (Downstream)​
NGK #23099 - Bank 2, Sensor 2 (Downstream)​

2001-2003
NGK #23139 - Bank 1, Sensor 1 (Upstream)​
NGK #23138 - Bank 2, Sensor 1 (Upstream)​
NGK #23142 - Bank 1, Sensor 2 (Downstream)​
NGK #23141 - Bank 2, Sensor 2 (Downstream)​
2004
NGK #23137 - Bank 1, Sensor 1 (Upstream)​
NGK #23135 - Bank 2, Sensor 1 (Upstream)​
NGK #23132 - Bank 1, Sensor 2 (Downstream)​
NGK #23531 - Bank 2, Sensor 2 (Downstream)​
2005-2006
NGK #23018 - Bank 1, Sensor 1 (Upstream)​
NGK #23160 - Bank 2, Sensor 1 (Upstream)​
NGK #23159 - Bank 1, Sensor 2 (Downstream)​
NGK #23158 - Bank 2, Sensor 2 (Downstream)​


Important Note About 1997-2000 NGK / NTK O2 Sensors
Per this post here, it appears as if NGK / NTK dropped the numbers for the 1997-2000 model year Jeeps with the 4.0 and 2.5 engines. They said that they are going through a "redesign" and that there "should be" new numbers for those years "sometime" in the near future.


Misc Installation Notes
When installing new O2 sensors, be certain to use some anti-seize on the threads of the new O2 sensors! This is important, and will save you a huge headache should you ever need to remove them in the future.

In addition, a O2 sensor socket will greatly aide in the installation and removal of O2 sensors. I recommend this one.

Lastly, if you notice your O2 sensor harnesses are not long enough with the new O2 sensors, these O2 sensor extensions will solve the problem.

Thanks Chris , This sticky , So usefull to me !
 
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New to jeeps and TJs, I have a 1997 TJ, 4 cyl 5 speed, code reader shows po138 and 141. Go to check the downstream o2 sensor. Not there! only a hanging electrical plug over the transfer case. Also a metal plug in the catalytic converter. Is this a PO previous owner thing or did any TJs come with one O2 sensor?
Thanks suva39
 
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New to jeeps and TJs, I have a 1997 TJ, 4 cyl 5 speed, code reader shows po138 and 141. Go to check the downstream o2 sensor. Not there! only a hanging electrical plug over the transfer case. Also a metal plug in the catalytic converter. Is this a PO previous owner thing or did any TJs come with one O2 sensor?
Thanks suva39

Previous owner, definitely!!

Both itterations of the '97 (early and late) had 2 sensors, pre and post cat. You want to make sure you pay close attention to the production date when looking for parts and sensors.
 
I’m assuming since this hasn’t been updated, the ntk 97-00 o2 sensors aren’t available yet. I’m getting bad gas mileage, replaced spark plugs, didn’t make a difference. Do I just need to wait until ntk o2 sensors for a 98 tj are available to try to see if that’s the problem? Any other options? Thanks!
 
I’m assuming since this hasn’t been updated, the ntk 97-00 o2 sensors aren’t available yet. I’m getting bad gas mileage, replaced spark plugs, didn’t make a difference. Do I just need to wait until ntk o2 sensors for a 98 tj are available to try to see if that’s the problem? Any other options? Thanks!

The best thing to do would be to call NTK/NGK directly.

I haven't followed up with them since I talked to them in mid October.
 
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My 05 rubicon LJ 4.0 O2 sensor harness plugs don’t match up w the new NTK 23018 and 23160 upstream sensors ????

Two things come to mind as to why they don't fit.
1. A previous owner spliced in different harness side plugs to fit incorrect sensors
2. The sensors you got are packaged incorrectly.

The NGK/NTK site isn't showing O2 sensor information any more for TJs unfortunately.
RockAuto is showing those same numbers for the Bank 1 and 2 Upstream sensors and the information in the first post was accurate as of the last time I spoke with a tech at NTK, which was back in October.

It's looking more like they dropped them all together after seeing their site today.
 
Two things come to mind as to why they don't fit.
1. A previous owner spliced in different harness side plugs to fit incorrect sensors
2. The sensors you got are packaged incorrectly.

The NGK/NTK site isn't showing O2 sensor information any more for TJs unfortunately.
RockAuto is showing those same numbers for the Bank 1 and 2 Upstream sensors and the information in the first post was accurate as of the last time I spoke with a tech at NTK, which was back in October.

It's looking more like they dropped them all together after seeing their site today.

Hey guys, new here but usually lurk and find my answers.

Anyways, I talked to NTK today (Actually Monarch Products) and they basically said these sensors have not been dropped and they also wouldn't say that they are developing new ones.

I called Napa today and he checked nationwide inventory and there are a bunch scattered across the country. I ordered online and it should be here in 2 days. If it actually arrives I will report back that this might be a source for now.
 
Maybe I should pick up some spares. The NTK ones are listed on RockAuto and show to be in stock. I bought a couple of them a month and a half ago and they worked great.
 
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Hey guys, new here but usually lurk and find my answers.

Anyways, I talked to NTK today (Actually Monarch Products) and they basically said these sensors have not been dropped and they also wouldn't say that they are developing new ones.

I called Napa today and he checked nationwide inventory and there are a bunch scattered across the country. I ordered online and it should be here in 2 days. If it actually arrives I will report back that this might be a source for now.

NTK/NGK isn't owned by Monarch... Monarch sells NGK products.

I spoke directly with NTK back in October and here's the link to what they told me then. At the time you could still look up the application data for O2 sensors for TJs. Since then they nolonger support the O2 sensor look up...

https://wranglertjforum.com/threads...-tj-oxygen-o2-sensor-thread.4068/post-1210205



As far as finding a source for future purchases, my guess is when all the supply houses sell out that'll be it... unless NTK starts producing them again.
 
NTK/NGK isn't owned by Monarch... Monarch sells NGK products.

I spoke directly with NTK back in October and here's the link to what they told me then. At the time you could still look up the application data for O2 sensors for TJs. Since then they nolonger support the O2 sensor look up...

https://wranglertjforum.com/threads...-tj-oxygen-o2-sensor-thread.4068/post-1210205



As far as finding a source for future purchases, my guess is when all the supply houses sell out that'll be it... unless NTK starts producing them again.

I jumped on their website today. It appears that they list them under PART FINDER and give a list of sellers under WHERE TO BUY (at least for the 2006)

1679425451981.png




1679425382922.png
 
I jumped on their website today. It appears that they list them under PART FINDER and give a list of sellers under WHERE TO BUY (at least for the 2006)

View attachment 409214



View attachment 409213

Good they finally put it back up. It's been a while since I checked, life and all that day to day mundane stuff..


@Chris it looks like they have the information back up, but after a quick peak a the 2000 m/y they have changed some numbers around.

Here's what they changed for the 2000 CA emissions. I think they messed up their list, because the original part numbers are still being used just in the wrong positions and the 23110 is new for a down stream. I have not called them to see if it's an error or not...
1679430059839.png
 
Good they finally put it back up. It's been a while since I checked, life and all that day to day mundane stuff..


@Chris it looks like they have the information back up, but after a quick peak a the 2000 m/y they have changed some numbers around.

Here's what they changed for the 2000 CA emissions. I think they messed up their list, because the original part numbers are still being used just in the wrong positions and the 23110 is new for a down stream. I have not called them to see if it's an error or not...
View attachment 409240

This seems to be a never ending guessing game with the 2000 model year. Maybe I'll go edit the original post and put some disclaimers in there about how we don't know if this is an error or not, but the part numbers are pulled directly from the NTK website.
 
This seems to be a never ending guessing game with the 2000 model year. Maybe I'll go edit the original post and put some disclaimers in there about how we don't know if this is an error or not, but the part numbers are pulled directly from the NTK website.

I was thinking something along that line too. I'd leave the numbers as you already have them, maybe just suggest calling NGK/NTK if there's a discrepancy between the list and NTK's parts finder.

Also I have not checked against any other years post 2000... '97 through '99 are all the same as before.
 
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My 05 rubicon LJ 4.0 O2 sensor harness plugs don’t match up w the new NTK 23018 and 23160 upstream sensors ????

Yup. Mine didn't either. However the male/female connectors would join, just the plastic locking jacket didn't match up....made it so you couldn't join 'em. Sos I just got the old nibblers out and nibbled the outer connector jacket of the replacement sensor until I could join the connectors. Been passing for two years.
 
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Friend of mine is looking to replace the upstream on his '98 6cyl. NTK #23151 seems to have left the chat availability wise. Anyone got any ideas on how to proceed?
 
Friend of mine is looking to replace the upstream on his '98 6cyl. NTK #23151 seems to have left the chat availability wise. Anyone got any ideas on how to proceed?

Best thing to do is call NTK tech line directly. I'm sure eventually all the TJ specific sensors are probably going to go the way of the dodo. I'm hoping that they might still have sensors that will fit the parameters, but they may have to be spliced in instead of plug and play.
 
Has anyone who has a comparable year TJ 2000 tried Walker 02 Sensors? We're they any good? Need to replace my NTK 23122 Sensor seeing as how NTK quit making that sensor. Wondering what to use...
 
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Looks like Rock Auto has two Mopar O2 sensors for my 97. Since the NGKs are AWOL should I go with these? Or call Napa tomorrow and see if they can find new old stock somewhere.

My "Mopar" oil sensor from Amazon is also starting to misbehave... probably order a Standard Motor Products while I'm at it.

Gas mileage has dropped to 10ish...was up to 13...O2s are the only sensors I haven't replaced. And my connectors are all zip tied together.

-Mac
 
Looks like Rock Auto has two Mopar O2 sensors for my 97. Since the NGKs are AWOL should I go with these? Or call Napa tomorrow and see if they can find new old stock somewhere.

My "Mopar" oil sensor from Amazon is also starting to misbehave... probably order a Standard Motor Products while I'm at it.

Gas mileage has dropped to 10ish...was up to 13...O2s are the only sensors I haven't replaced. And my connectors are all zip tied together.

-Mac

That all depends on how ambitious your local Napa guys are... Also have you checked Amazon yet?