The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread


Chris

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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":

Oxygen 02 Sensor FAQ and Information - Jeep Forum.jpg



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).


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
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)​
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.
 

CommandoJoe

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Location
Vancouver, WA
I just replaced all of the O2 sensors on my 2004 4.0, and Rockauto shows NTK 23531 for bank 2 sensor 2 instead of 23131... Did I put the wrong one in or are these interchangeable? I haven't had any issues in the month since I installed it though.

Also, for those here researching O2 sensor codes, mine threw an O2 sensor code, but I'm not sure any were actually bad, because the root of the problem was one of the precats broke up and was clogging the exhaust... But I was at 90k miles and decided to replace all the sensors anyway while I replaced the cats. So make sure there isn't some other problem causing the O2 code. If you're on all original parts and getting up there in miles it might be a good idea to just replace everything anyway - it's easier to access the O2 sensors when the downpipe is out. Total cost for 4 sensors and downpipe with precats and new cat was about $450. I probably could have saved a few $ somewhere else, but Rockauto was able to get everything to me the fastest.
 
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Chris

Chris

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I just replaced all of the O2 sensors on my 2004 4.0, and Rockauto shows NTK 23531 for bank 2 sensor 2 instead of 23131... Did I put the wrong one in or are these interchangeable? I haven't had any issues in the month since I installed it though.

Nope, you're right, I'm wrong!

I had typed 23131, when it was actually 23531... In other words, my fat finger hit the 1 instead of the 5!

I'll go back and double check I didn't do that with any others. Thanks for the heads up, much appreciated!
 
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Ken97

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Timmins, ON, Canada
Thanks for such a great resource! A couple of my O2 sensors have gone bad (soooo hard on fuel!) so I'm replacing all 4 as preventative maintenance.
 
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Chris

Chris

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Thanks for such a great resource! A couple of my O2 sensors have gone bad (soooo hard on fuel!) so I'm replacing all 4 as preventative maintenance.

Good idea! For the price, it makes sense to do them all at once!
 

Ken97

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Good idea! For the price, it makes sense to do them all at once!

All replaced and no more error codes! Hopefully my mileage improves.

*To anyone looking to replace their O2 sensors* I'd reccomend a breaker bar, penetrating lube, and some kind of torch (all I had was a small propane torch). It took me just over 2 hours to do all mine and the breaker bar (or pipe slid over a ratchet) was needed a few times. I also bought the O2 sensor socket for $10 and it was totally worth it. Total investment was about $250 for all 4 sensors plus the socket.
 
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Chris

Chris

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All replaced and no more error codes! Hopefully my mileage improves.

*To anyone looking to replace their O2 sensors* I'd reccomend a breaker bar, penetrating lube, and some kind of torch (all I had was a small propane torch). It took me just over 2 hours to do all mine and the breaker bar (or pipe slid over a ratchet) was needed a few times. I also bought the O2 sensor socket for $10 and it was totally worth it. Total investment was about $250 for all 4 sensors plus the socket.

Yep, they likely didn't have anti-seize on the old ones.

As I mentioned in my original post, 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. You know first hand what I'm talking about now!
 

Ken97

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Messages
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Timmins, ON, Canada
Yep, they likely didn't have anti-seize on the old ones.

As I mentioned in my original post, 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. You know first hand what I'm talking about now!

10/10 would recommend anti-seize. The sensors I bought came with anti seize already on the threads but I added extra just to be safe
 
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Chris

Chris

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I got a lot of info from this thread Chris and I took your advice regarding NGK parts. I finally had the time to replace the sensors and now it idles like a dream. I appreciate all your work.

Good to know! The NGK O2 sensors aren't that much, and they're the only sensor out there that is proven to work with our finicky TJs. Definitely not worth saving a few dollars to go with the crappy Chinese ones they sell at your local auto part stores.
 

Buffalo

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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.

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).

4 Cylinder Engines

1997-2000

NGK #23506 - Bank 1, Sensor 1 (Upstream)
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

1997-1998
NGK #23151 - Bank 1, Sensor 1 (Upstream)
NGK #23099 - Bank 2, 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)

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.
I
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.

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).

4 Cylinder Engines

1997-2000

NGK #23506 - Bank 1, Sensor 1 (Upstream)
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

1997-1998
NGK #23151 - Bank 1, Sensor 1 (Upstream)
NGK #23099 - Bank 2, 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)

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.