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The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread

BigDan

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Aug 21, 2021
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Location
St-Jean Baptiste , Quebec.
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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Suva39

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Joined
Nov 17, 2022
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Location
Rhode Island
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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reddvltj

TJ Guru
Supporting Member
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Apr 15, 2019
Messages
6,829
Location
Challis, ID
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.