The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread

I have burned up (broken inside shell) 3 Cat converts in the past 5K miles. I have 2000 TJ (55K miles, original owner) with 1 upstream and 1 downstream sensor. No codes thrown, runs/idles fine ... but after a few trail runs the CATCO replacements start to rattle (and break up).

Spent about $1K trying to get to root cause and trusting my rig again. I had it stressed tested on dyno and it leans/trims out fine. Took it to some mechanic's mechanic (w/aftermarket sensor tools) that show nothing is wrong (except that I am missing 2 sensors).

Finally, took it to dealer to confirm old computer software IS working, but they noticed slow response in upstream O2. Still, they said the likely problem is too much air flow from aftermarket cold air intake.

This forum said ... "the dealer statement about CAI allowing too much air is junk".

I am thinking to replace both O2 sensors, but a 2 sensors 2000 TJ is an "odd duck", as stated earlier. Even the NGK site is expecting 4 sensors on this duck.

1.) Can I get a definitive NGK part match??

2000 was the odd-ball year where some models had the earlier system with only 1 cat and 2 O2 sensors, whereas later models had the 2 pre-cats and the 4 sensors. If yours is the earlier style with 2 sensors, follow the O2 sensor guidelines in the original post for the 1999 model is what I would suggest.

And yes, the CAI intakes aren't any good for these 4.0 engines. I know so many people want to believe they are, but that much has been debunked so many times. Spare yourself, your engine (and your cats) by switching back to a stock airbox and air filter. Even those K&N filters people use in the stock airboxes let too many contaminates through.
 
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@Chris

I have a CEL with the P0431 code. The previous owner worked in the automotive shop at the dealership, and he said he had the cats checked several times, but they were definitely good. So he just cleared the codes, but it kept coming back.

I'm planning on starting with changing out the B2S2 sensor, then clear the codes and see what happens.

If that doesn't work, and I find out the cats are bad, do you have a recommendation for which cat to buy? I found a Magnaflow cat on Amazon for $45 used or $65 brand new. It says it fits my Jeep, but wanted to make sure. And are both cats identical?

Thanks for any advice!!
 
@Chris

I have a CEL with the P0431 code. The previous owner worked in the automotive shop at the dealership, and he said he had the cats checked several times, but they were definitely good. So he just cleared the codes, but it kept coming back.

I'm planning on starting with changing out the B2S2 sensor, then clear the codes and see what happens.

If that doesn't work, and I find out the cats are bad, do you have a recommendation for which cat to buy? I found a Magnaflow cat on Amazon for $45 used or $65 brand new. It says it fits my Jeep, but wanted to make sure. And are both cats identical?

Thanks for any advice!!

Make sure the sensors that are in there are NGK sensors, otherwise the codes will keep coming back (that's why I mentioned it in the original post). There's a good chance that's the issue here, is that the previous owner didn't use NGK sensors.

As for cat recommendations, what year is your TJ?
 
Make sure the sensors that are in there are NGK sensors, otherwise the codes will keep coming back (that's why I mentioned it in the original post). There's a good chance that's the issue here, is that the previous owner didn't use NGK sensors.

As for cat recommendations, what year is your TJ?

I'm sorry! I meant to put that in my post.

It's a 2005 X, so it's the 4.0L.
 
I'm sorry! I meant to put that in my post.

It's a 2005 X, so it's the 4.0L.

So I assume it's the pre-cats you need, right? The two in the downpipe?

If so, these are the ones I used on my 2005:
https://www.amazon.com/dp/B001AGP864/?tag=wranglerorg-20

These ones also work as well:
https://www.amazon.com/dp/B06XMXC6YK/?tag=wranglerorg-20
https://www.amazon.com/dp/B0031G6YT6/?tag=wranglerorg-20
https://www.amazon.com/dp/B0027A6PAA/?tag=wranglerorg-20

If you're talking about the single cat that is underneath the vehicle above the skid plate, you can use any catalytic converter for that one as it isn't specific. I removed that cat altogether.
 
So I assume it's the pre-cats you need, right? The two in the downpipe?

If so, these are the ones I used on my 2005:
https://www.amazon.com/dp/B001AGP864/?tag=wranglerorg-20

These ones also work as well:
https://www.amazon.com/dp/B06XMXC6YK/?tag=wranglerorg-20
https://www.amazon.com/dp/B0031G6YT6/?tag=wranglerorg-20
https://www.amazon.com/dp/B0027A6PAA/?tag=wranglerorg-20

If you're talking about the single cat that is underneath the vehicle above the skid plate, you can use any catalytic converter for that one as it isn't specific. I removed that cat altogether.

Ok, you'll have to forgive me because I know NOTHING about exhaust systems. Which cat would likely be throwing the P0431 code if it isn't the O2 sensor?

Any I'll effects from just removing that third cat? I'm in Missouri so I don't have to worry about emmission standards tests .
 
Ok, you'll have to forgive me because I know NOTHING about exhaust systems. Which cat would likely be throwing the P0431 code if it isn't the O2 sensor?

Any I'll effects from just removing that third cat? I'm in Missouri so I don't have to worry about emmission standards tests .

That would be the pre-cats, the ones I've linked to above. Those are the two cats in the downpipes that are known for going bad and throwing these codes. The cat that is underneath the vehicle has nothing to do with any codes whatsoever.
 
I have a 2005 Sport with the 4.0 that is throwing a P0137 code. When searching Amazon it is calling for an NTK 23158 to fit Bank 1 Sensor 2 and not an NTK 23159 like this thread is saying. In fact Amazon is saying the 23159 won’t even fit the Jeep at all. Can someone confirm or deny this?
Thanks in advance for any help.
 
2004 TJL. Code P0420. 200K miles. Magna flow cat back. Runs fine 14 city 20 Hwy. Should I bite the bullet and replace the down pipe with the cats and all new sensors or what?
 
2004 TJL. Code P0420. 200K miles. Magna flow cat back. Runs fine 14 city 20 Hwy. Should I bite the bullet and replace the down pipe with the cats and all new sensors or what?
I’m in the same boat with my 2005 with code p0421. I have no other codes. If I clear it, it keeps coming back. Jeep is also running fine without any other problems I can find. Also just replaced plugs and cleaned air filter. When this is the case, and there are no other codes or rich/lean issues, I think the advice is to replace the DP with the two cats. That is what I’ll be doing.
 
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Anybody else had an issue with the length of the 02 sensor cable for their '97 Jeep TJ 4.0?

I've had the error 21 issue for a while, finally got around to ordering the part for the upstream sensor. Received the NTK 23151 O2 sensor, but looking at the cable it really seems like there's no chance it will reach from where the sensor inserts, all the way up to where the connection is by the steering column.

I don't really want to open the packaging and not be able to return it if I'm right. It looks like I would need about double the length I got.
 
Anybody else had an issue with the length of the 02 sensor cable for their '97 Jeep TJ 4.0?

I've had the error 21 issue for a while, finally got around to ordering the part for the upstream sensor. Received the NTK 23151 O2 sensor, but looking at the cable it really seems like there's no chance it will reach from where the sensor inserts, all the way up to where the connection is by the steering column.

I don't really want to open the packaging and not be able to return it if I'm right. It looks like I would need about double the length I got.

Someone else had this issue, just can't remember who!
 
I’m in the same boat with my 2005 with code p0421. I have no other codes. If I clear it, it keeps coming back. Jeep is also running fine without any other problems I can find. Also just replaced plugs and cleaned air filter. When this is the case, and there are no other codes or rich/lean issues, I think the advice is to replace the DP with the two cats. That is what I’ll be doing.
2004 TJL. Code P0420. 200K miles. Magna flow cat back. Runs fine 14 city 20 Hwy. Should I bite the bullet and replace the down pipe with the cats and all new sensors or what?

I had the p0431 code on my 2006 with 65k miles a few weeks ago. I put new NTK o2 senors in and the code came back. I ended up just replacing the cats since I had read that they tendancy to fail around 60k miles. I've driven around 500 miles since replacing the cats and no codes have came back.
 
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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
 
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
How fat are you? even without jack, you can access them.
 
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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

You've just got to be a contortionist of sorts in order to get to some of them, haha.
 
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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

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?
 
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When I click on NGK #23159 for my 2006 TJ, Amazon says this sensor doesn't fit my Jeep. Is this an Amazon error or is there a different sensor that fits? Thanks.
 
When I click on NGK #23159 for my 2006 TJ, Amazon says this sensor doesn't fit my Jeep. Is this an Amazon error or is there a different sensor that fits? Thanks.

That's an Amazon error. This is taken directly from the NGK website for a 2006 TJ:

Screen Shot 2018-07-04 at 1.38.28 PM.png


You'll see NGK #23159 is indeed the right one for the Bank 1 Sensor 2 position.