The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread

Joined
Jan 30, 2020
Messages
27
Location
Indianapolis, IN
I'm not so much worried about emissions, they're non-existent where I live, I just want to keep the CEL gremlins from harassing me until the ECU gets it's reprogram

Update: Just talked to NGK rep and he had me go to and use their part finder. It does have listings for Federal and CA emissions.
2000 4.0l 5spd
Federal emissions (Only 2 sensors)
23122 upstream
23099 downstream
Did that work out?

I'm dealing with the same. Unless I'm mistaken, my 2000 4.0 only has two underneath, with plugs covering the two under the hood. Also, no O2 (CA) fuse.

According to NGKs site this should be 23122 and 23099, which is contradicting.
 

reddvltj

TJ Addict
Supporting Member
Joined
Apr 15, 2019
Messages
1,382
Location
Challis, ID
Did that work out?

I'm dealing with the same. Unless I'm mistaken, my 2000 4.0 only has two underneath, with plugs covering the two under the hood. Also, no O2 (CA) fuse.

According to NGKs site this should be 23122 and 23099, which is contradicting.
I haven't gotten around to replacing my O2 sensors yet, since I replaced the spark plugs I haven't got another code.
I'm not quite sure what "plugs" you're referring to under the hood. As to the difference between Fed and CA emissions on the 2000 model 4.0l, the CA emissions has 2 "pre-cats" directly below the exhaust manifold with an 02 sensor just after each of those. The Federal emissions model has the same style exhaust manifold but no pre-cats.
If you in fact have the Federal Emissions then the 2 NTK numbers you stated are correct.

2000 Federal Emissions The 2 sensors are located under the body tub, one in front of the cat before the flange, and the other after the cat (not pictured here)
1581450599982.png
2000 CA Emissions The 2 up stream sensors are directly below the pre-cats and the 2 down stream are before and after the main cat.
1581450644042.png
 
Joined
Jan 30, 2020
Messages
27
Location
Indianapolis, IN
I haven't gotten around to replacing my O2 sensors yet, since I replaced the spark plugs I haven't got another code.
I'm not quite sure what "plugs" you're referring to under the hood. As to the difference between Fed and CA emissions on the 2000 model 4.0l, the CA emissions has 2 "pre-cats" directly below the exhaust manifold with an 02 sensor just after each of those. The Federal emissions model has the same style exhaust manifold but no pre-cats.
If you in fact have the Federal Emissions then the 2 NTK numbers you stated are correct.

2000 Federal Emissions The 2 sensors are located under the body tub, one in front of the cat before the flange, and the other after the cat (not pictured here)
View attachment 139629
2000 CA Emissions The 2 up stream sensors are directly below the pre-cats and the 2 down stream are before and after the main cat.
View attachment 139630
I haven't gotten around to replacing my O2 sensors yet, since I replaced the spark plugs I haven't got another code.
I'm not quite sure what "plugs" you're referring to under the hood. As to the difference between Fed and CA emissions on the 2000 model 4.0l, the CA emissions has 2 "pre-cats" directly below the exhaust manifold with an 02 sensor just after each of those. The Federal emissions model has the same style exhaust manifold but no pre-cats.
If you in fact have the Federal Emissions then the 2 NTK numbers you stated are correct.

2000 Federal Emissions The 2 sensors are located under the body tub, one in front of the cat before the flange, and the other after the cat (not pictured here)
View attachment 139629
2000 CA Emissions The 2 up stream sensors are directly below the pre-cats and the 2 down stream are before and after the main cat.
View attachment 139630
Understood. I appreciate the explanation, that is what I have then. I was confusing the hex head on the bottom of the manifold where the original illustration is showing a sensor.

Hope the code stays at bay for you.
 
  • Like
Reactions: reddvltj

JMT

The Jeep Guy
Supporting Member
Ride of the Month Winner
Joined
Feb 27, 2017
Messages
9,948
Location
Washington
@Chris, not sure what’s going on here. I bought the B2S1 NTK linked to in original post for a 2005 TJ. Part No. 23160. It is the same one in the NGK website as well. But the harness connects slightly different. See pics below:

Note on the left side of each connector the c channel is lower in the original than on the replacement. Because if this they won’t slide together
38C21B06-0F45-4862-B2A2-DF5C3D728073.jpeg

Image below is from the NGK website. It’s just like the one I ordered above, but won’t fit.

7327F0FC-8E76-4C7C-9054-7C54584AB50A.jpg
 
OP
Chris

Chris

Administrator
Staff Member
Joined
Sep 28, 2015
Messages
45,067
Location
Salem, Oregon
@Chris, not sure what’s going on here. I bought the B2S1 NTK linked to in original post for a 2005 TJ. Part No. 23160. It is the same one in the NGK website as well. But the harness connects slightly different. See pics below:

Note on the left side of each connector the c channel is lower in the original than on the replacement. Because if this they won’t slide together
View attachment 140438
Image below is from the NGK website. It’s just like the one I ordered above, but won’t fit.

View attachment 140439
Wow, that's really, really odd. I never had this issue when I did mine.

While I don't know why this is, you know what I would do? Take the connector from your old one and reuse it on the new one.

If you have these types of wiring tools, it's a piece of cake to swap connectors:

https://www.amazon.com/dp/B082FDGVD9/?tag=wranglerorg-20
 

JMT

The Jeep Guy
Supporting Member
Ride of the Month Winner
Joined
Feb 27, 2017
Messages
9,948
Location
Washington
Wow, that's really, really odd. I never had this issue when I did mine.

While I don't know why this is, you know what I would do? Take the connector from your old one and reuse it on the new one.

If you have these types of wiring tools, it's a piece of cake to swap connectors:

https://www.amazon.com/dp/B082FDGVD9/?tag=wranglerorg-20
I know, you’ve had ‘05’s. This is a mystery to me. It made me think either the part no was wrong or something happened in the OEM manufacturing of my rig (which would be so odd).
I may look further into this before cutting the wires and using the old harness
 
  • Like
Reactions: Chris
OP
Chris

Chris

Administrator
Staff Member
Joined
Sep 28, 2015
Messages
45,067
Location
Salem, Oregon
I know, you’ve had ‘05’s. This is a mystery to me. It made me think either the part no was wrong or something happened in the OEM manufacturing of my rig (which would be so odd).
I may look further into this before cutting the wires and using the old harness
No need to cut the wires if you use those tools I posted the link to.

But yes, if you look into it further, I'd be curious to hear what you find.
 
  • Like
Reactions: JMT

Spencer C

New Member
Joined
Feb 9, 2020
Messages
2
Location
Tallahassee, FL
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).


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.
is there any particular reason the amazon links for the 2004 4.0 sensors are SIGNIFICANTLY cheaper than ordering from Napa or Autozone? Just wanna make sure I’m getting legit parts
 
OP
Chris

Chris

Administrator
Staff Member
Joined
Sep 28, 2015
Messages
45,067
Location
Salem, Oregon
is there any particular reason the amazon links for the 2004 4.0 sensors are SIGNIFICANTLY cheaper than ordering from Napa or Autozone? Just wanna make sure I’m getting legit parts
Yes, because amazon is almost always cheaper than those places. The sensors are real. Go read through this thread it in doubt. Everyone gets them from amazon 👍
 
  • Like
Reactions: reddvltj

bagpiper22

New Member
Joined
Feb 11, 2020
Messages
6
Location
Norwalk, CT
Hey, be sure to check RockAuto. I've got a 2001 and I got genuine NTK sensors at a better price than amazon prime, even with paying for shipping factored in.
 
  • Like
Reactions: reddvltj

rokryder

New Member
Joined
Mar 17, 2020
Messages
12
Location
Crawfordville, FL
Newbie on this forum and I have a ridiculous problem...I cannot get the electrical connector to come apart on my O2 sensors! The downstream one appears to be original on my 2002 SE 2.5 and the red flag portion was brittle and snapped with little provocation. I can see the latch move, but no amount of wiggling would get them to separate. If there’s a trick, I haven’t figured it out yet.
I didn’t need to replace the sensor...the Jeep runs great. I am replacing the clutch and the manual said “remove parts of the exhaust as necessary”. I figured I would at least need to pull the cat off, but now I am not sure that it will be required. So that’s how I started futzing around with the O2 sensor. I have the socket and got it out with little problem (there was enough slack in the cable to remove the sensor by allowing the wires to twist gently) If I don’t need to pull the cat, then I will just put the sensor back...although it wouldn’t hurt to go ahead and change them both out now that I’m partway there...if I can only get the bloody connectors off!
Approaching 70, I no longer have the strength of my youth, but I have wrenched for years and have a lift, high lift transmission jacks and a well equipped shop.
I am embarrassed to be flummoxed by two little electrical connectors...

Kim
 

reddvltj

TJ Addict
Supporting Member
Joined
Apr 15, 2019
Messages
1,382
Location
Challis, ID
Newbie on this forum and I have a ridiculous problem...I cannot get the electrical connector to come apart on my O2 sensors! The downstream one appears to be original on my 2002 SE 2.5 and the red flag portion was brittle and snapped with little provocation. I can see the latch move, but no amount of wiggling would get them to separate. If there’s a trick, I haven’t figured it out yet.
I didn’t need to replace the sensor...the Jeep runs great. I am replacing the clutch and the manual said “remove parts of the exhaust as necessary”. I figured I would at least need to pull the cat off, but now I am not sure that it will be required. So that’s how I started futzing around with the O2 sensor. I have the socket and got it out with little problem (there was enough slack in the cable to remove the sensor by allowing the wires to twist gently) If I don’t need to pull the cat, then I will just put the sensor back...although it wouldn’t hurt to go ahead and change them both out now that I’m partway there...if I can only get the bloody connectors off!
Approaching 70, I no longer have the strength of my youth, but I have wrenched for years and have a lift, high lift transmission jacks and a well equipped shop.
I am embarrassed to be flummoxed by two little electrical connectors...

Kim
Have you tried using a little penetrating fluid?
 

rokryder

New Member
Joined
Mar 17, 2020
Messages
12
Location
Crawfordville, FL
Have you tried using a little penetrating fluid?
Actually, yes. I may break out some vice-grips to get a better grip on the two halves, but I suspect it may be a little brittle due to age and I am trying to avoid KOing the thing. I feel it's silly, as I have worked on stuff for decades, and have had no problems with other emission control connections, but these little guys gave me fits.

I appreciate any and all suggestions!
Kim
 
  • Like
Reactions: reddvltj

bagpiper22

New Member
Joined
Feb 11, 2020
Messages
6
Location
Norwalk, CT
Hey. Struggling to get downstream rear sensor out. 2001 4.0 116k. Throwing P0158. I have the new sensors but the old one won’t budge. I’ve got both inline and offset O2 sockets. Tried heat (propane) and days of PB blaster. At this point the sensor is rounded off so I can try about anything, but my question is this:

has anybody disconnected the front driveshaft to have better access to the sensor? I feel like I could move it out of the way and get better leverage around the sensor. Or am I asking for trouble? Should I go get a MAP torch?

B156E3EF-4BC2-44E0-972F-8989E0DDB955.jpeg

CBD85057-CA39-4A02-990E-BB41C021F6DC.jpeg



Thanks in advance
FC7DA803-9630-4DF2-956B-64607F7ED2A7.jpeg
 

Reign Mack

TJ Enthusiast
Supporting Member
Joined
Nov 30, 2015
Messages
956
Location
London England
Is it safe to keep driving with P0138 ? I have ordered the part I need but with whats currently going on its probably going to take a month to arrive.