The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread

It depends on where you have to work, if you have a lift, oversized tires, etc. I just have coil spacers (I believe 1.75" and 31x10.50 tires. So not much of a lift. But that gives me plenty of room to crawl up underneath in my apartment parking lot and get to all four O2 sensors. Now the plugs? Those can be hard to reach, as you have to reach up and around some things on a couple of them.

If your Jeep is stock height, maybe you have an uneven surface to work on, or you're a stocky guy, you might have some issues. In that case I'd go grab some $40 ramps and drive it up on them.

Look at it this way, I've never heard anyone complain that they had TOO MUCH room to work under their vehicle. I mean, who doesn't want to feel claustrophobic?
Thankfully, I have a gf with skinny arms. :)
 
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Ok, I know little enough about engines that is will sound like a stupid question, but here it goes...how do you change out the O2 sensors without some sort of lift ( or ramps)?I know at least one is fairly easy to get to, but a couple of them, I just don’t see how it’s possible? (05 X). Thanks
I have an 05 X as well, and once you get the first one replaced, you actually start to get into a little bit of a rhythm, and the rest are reasonably easy to swap out. For the pre-cat sensors, coming at them from the top may or may not be the best way to get at them. But for me, it was still a solid option. If you do end up having to come in from the top, it's never a bad idea to check the mounting bolts on your exhaust header as well to make sure they're secure, since some O2 CEL codes can come from air leaks in the header.
 
Thanks for this guide! I just replaced all 4 in my ‘06 LJ, along with new spark plugs - it is running so smooth and strong :). We’ll see if mpg changes. I got lucky and they broke loose easy with a half turn of the removal tool linked in the original post. After that they turned out easy by hand - phew.
 
Someone else had this issue, just can't remember who!

Yea after looking at a few other threads and diagrams I think a previous owner installed a different exhaust system, because the location of the upstream o2 sensor is way off from what I've been seeing. Went to a shop and got them to splice the new one to be much much longer.
 
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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 #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 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.
Chris - you rock my friend! This is by far the best forum on the WEB. Thanks to you and all of the members who contribute their time, ideas and knowledge!

Lou
 
Chris - you rock my friend! This is by far the best forum on the WEB. Thanks to you and all of the members who contribute their time, ideas and knowledge!

Lou

No problem, and thank you! Always happy to help fellow TJ owners!
 
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I'm hoping someone here can help, I've got a 2006 Wrangler. All parts websites say sensor #23158 is correct for bank 2 sensor 2.

I ordered it from amazon and saw 2 reviews that said it didn't work on their 06 Wrangler, but I ordered it anyway because this forum also confirmed the part number. Well received it today and it's not right, the plug is definitely different. In the picture, the plug on the left is from sensor #23158 and the one on the right is my current sensor plug

Has anyone else had this problem? Someone mentioned cutting and soldering the old plug on the new sensor but I'm not really comfortable with that

Screenshot_2018-08-02-12-08-21.png
 
1999 TJ, been trying to get the downstream sensor out. I used a ton of PB Blaster and hit it with a propane torch with no luck using an open end wrench. I finally cut the wire and the top of the sensor (used a reciprocating saw) so I could get a socket on the flats. Was able to get a breaker bar on the socket, but it is so tight between the skid plate and the muffler that there is no way to turn it. Either the skid plate or the muffler has to come out and given the rust all around either job seems like trouble especially without a lift. Am I missing something?


o2sensor.jpg
 
1999 TJ, been trying to get the downstream sensor out. I used a ton of PB Blaster and hit it with a propane torch with no luck using an open end wrench. I finally cut the wire and the top of the sensor (used a reciprocating saw) so I could get a socket on the flats. Was able to get a breaker bar on the socket, but it is so tight between the skid plate and the muffler that there is no way to turn it. Either the skid plate or the muffler has to come out and given the rust all around either job seems like trouble especially without a lift. Am I missing something?

Nope, you're not missing anything. Yours is just so corroded in there that it's not budging. I will say that PB Blaster is garbage when compared to Kroil (I've used them both and can attest to this), so I may give Kroil a try.

If that doesn't do it, you could always take it to an exhaust shop and have them cut that section of the pipe out and weld a new one (with a bung) in place of it.
 
Nope, you're not missing anything. Yours is just so corroded in there that it's not budging. I will say that PB Blaster is garbage when compared to Kroil (I've used them both and can attest to this), so I may give Kroil a try.

If that doesn't do it, you could always take it to an exhaust shop and have them cut that section of the pipe out and weld a new one (with a bung) in place of it.


Thanks. I picked-up a MAP torch today and hit the bung until red spraying with WD40 Penetrating oil — repeated a few times — wouldn't budge. I think if I had room to get some leverage I might get it, but I don't have a lift to take off the muffler or skid plate. I have a local shop that I can take it to. Sucks that something so simple is so hard.
 
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Thanks. I picked-up a MAP torch today and hit the bung until red spraying with WD40 Penetrating oil — repeated a few times — wouldn't budge. I think if I had room to get some leverage I might get it, but I don't have a lift to take off the muffler or skid plate. I have a local shop that I can take it to. Sucks that something so simple is so hard.

You’re right about a lift and some leverage. I’ll bet that would do it. Sometimes you really need a lift to get that leverage.
 
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 #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 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.
Chris thanks for all the info. I'm going to be ordering all 4 sensors. I have a 05 sport and when I went to the link you have for the bank 1 sensor 2 it says it don't fit. Is there another one I could use? Thanks.

Screenshot_20180823-215411.png
 
Chris thanks for all the info. I'm going to be ordering all 4 sensors. I have a 05 sport and when I went to the link you have for the bank 1 sensor 2 it says it don't fit. Is there another one I could use? Thanks.

That is the correct O2 sensor, Amazon just has an error on their end by saying it doesn't fit your 2005.

This is taken from the official NGK website just now:

Screen Shot 2018-08-23 at 7.42.16 PM.png


As you can see, 23159 is indeed the correct O2 sensor.

Sometimes Amazon gets things wrong. Rarely, but it does happen.
 
That is the correct O2 sensor, Amazon just has an error on their end by saying it doesn't fit your 2005.

This is taken from the official NGK website just now:

View attachment 52671

As you can see, 23159 is indeed the correct O2 sensor.

Sometimes Amazon gets things wrong. Rarely, but it does happen.
Perfect. Thank you. I have a 05 with the 4.0 thanks again Chris.