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The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread

pacogamboa

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Apr 26, 2019
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6
Location
Tucson
Brought LJ to shop for replacement of exhaust manifold and cats...
They’ve replaced them but now the Jeep won’t run.
They started it and it shit down shortly after. They can’t make it run.

THOUGHTS?


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epbu

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May 13, 2019
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Finland
So for a 1997 2.5, I need to get:

2 - NGK #23506 - Bank 1, Sensor 1 (Upstream)
2 - NGK #23099 - Bank 1, Sensor 2 (Downstream)

??
I have -97 2.5 also.
Just received the "NGK #23506 - Bank 1, Sensor 1 (Upstream)" and it has 5 wires !? Gray, white, blue, yellow, black.
Old sensor only has 4 wires, 1 black and 3 white (no connector).
I'm not making sense in this. Can I disregard one of the 5 wires, which one?

sensor.jpg
 
OP
Chris

Chris

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I have -97 2.5 also.
Just received the "NGK #23506 - Bank 1, Sensor 1 (Upstream)" and it has 5 wires !? Gray, white, blue, yellow, black.
Old sensor only has 4 wires, 1 black and 3 white (no connector).
I'm not making sense in this. Can I disregard one of the 5 wires, which one?

View attachment 93556
Does the plug plug-in to your plug on the vehicle?
 

epbu

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Does the plug plug-in to your plug on the vehicle?
There is no plug on the vehicle.

I changed the bank 1 sensor 2 last year. There were different plugs in both ends, but I managed to connect the wires, because there were only 4 wires in both ends and I had help from NGK wire Diagram
 
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Chris

Chris

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There is no plug on the vehicle.

I changed the bank 1 sensor 2 last year. There were different plugs in both ends, but I managed to connect the wires, because there were only 4 wires in both ends and I had help from NGK wire Diagram
How is there no plug on the vehicle? You're telling me the factory O2 sensor wasn't plugged in to a plug?
 

epbu

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How is there no plug on the vehicle? You're telling me the factory O2 sensor wasn't plugged in to a plug?
I'm guessing both sensors have been changed by previous owners since the vehicle has 110000 miles on it.
 
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Chris

Chris

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I'm guessing both sensors have been changed by previous owners since the vehicle has 110000 miles on it.
Okay, I'm not sure what's going on in your situation then, sounds like something is up, though I have no idea what.
 

epbu

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Okay, I'm not sure what's going on in your situation then, sounds like something is up, though I have no idea what.
According to factory service manual, there is only 4 wires on the bank1 sensor1 but the recommended "NGK #23506" has 5 wires. Does anyond know, which of these five can be left out?
 
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Chris

Chris

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According to factory service manual, there is only 4 wires on the bank1 sensor1 but the recommended "NGK #23506" has 5 wires. Does anyond know, which of these five can be left out?
I haven't the slightest clue.

I do know however that that is the correct sensor according to the NGK website, so I'm not sure what's going on with that.

You may want to post a new thread about this for more attention. Your question is getting lost in an already long thread that most may not notice.
 

Mikester86

If at first you don't succeed, skydiving isn't 4 U
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Dec 6, 2018
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327
Location
Michigan
My 2001 threw a P0432 Code yesterday. The Jeep idles a little rough at start up , then appears to run fine. Will a code reader indicate the specific problem, as in the O2 sensor is bad, or the cat?
 
Last edited:

pacogamboa

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Apr 26, 2019
Messages
6
Location
Tucson
Update.

After changing:

Camshaft position sensor
TPS SENSOR
IAC snsor
O2 sensors
Intake manifold
Cats

It has now become a PCM problem.
Apparently the misfires are related to a faulty PCM.

Any advice?


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azroc909

TJ Enthusiast
Joined
Oct 10, 2018
Messages
164
Location
Big Texas
I just wanted to reply to this after replacing the catalytic converter AGIAN. I called Pacesetter. I have been in contact with them since I installed it. I had done a few test for them. They finally agreed to send me a new one under warranty. The flanges lined up perfectly this time and I had a buddy help me install. I used new original bolt and then lock flange nuts and a lock washer on top. Torqued to 22ftlb. It pressed in very nicely to the ball flanges but took a while with the back and forth on 4 bolts, however the pipe coming down and around was not lined up straight back. It also awfully close to the oil pan on the driver side as it comes down. So there is now a leak at the muffler flanger. I had to finished up as it was getting dark so we lined it up the best we could. I'm going to carefully take a floor jack to it later to push it up. It is well after the O2 sensors so it shouldn't affect the CEL codes. In the end after a week the codes have vanished. In my opinion pacesetter took the Y flange out of the weld jig too soon and it cooled and warped. DON'T purchase the pacesetter 324236. Even though it ever up ok in the end I think. Here was another review that said they don't line up on quadratec after I bought it. The emissions still say Not Ready so I have to do the TSB that the dealership wouldn't do. Even though it's under warranty I'm gonna tackle it myself. That Jeep dealership is the worst in South Florida.
Hello, would you mind giving an update on the pacesetter cats please, did they leak on the bottom connection with the clamp on did you fix muffler cat connection leak? Any issues besides what you stated above?
I bought the eastern cats but it leaks at the two piece joint section no matter how tight I have the clamp and I don’t want to weld it just in case I need to remove it.
Thanks
 

Dirwin

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Joined
Jun 4, 2019
Messages
1
Location
Atlanta
Update...

Changed all four O2 sensors.
Codes are back.
Loss of power with misfires.
Changing cats and while at it exhaust manifold.

Let’s see if it works.


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My jeep is throwing all 4 O2 sensors as bad. What happened with yours? Was it the Cats or PCM or?
 

jrussell505

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May 2, 2019
Messages
3
Location
Los Angeles, CA
I realize that this thread is from last year, and it was very helpful in determining sensor locations for me. But after replacing all sensors, and still throwing a O2 sensor code (heater circuit failure), I discovered the actual problem was a bad O2 sensor relay. So, for those chasing down O2 sensor codes, don't forget to check your relays.​
But what were the symptoms of a bad sensor relay? Fuel mileage drop? Or just not properly reporting that the sensors were working correctly?
 

jrussell505

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May 2, 2019
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Location
Los Angeles, CA
2003 TJ Rubicon here.
Used NTK sensors.

Replaced 1/1 and 2/1 sensors when my gas mileage went into the toilet around 5 MPG. It has come back up to 11 or so MPG but not to where it was before I swapped them out - the typical 15-ish.

My precats are bad so I wasn't going to change the downstream sensors based on what Jerry has written before - that the upstream sensor(s) are more responsible for affecting the severe gas mileage drop... if i read correctly.

If I swap the downstream ones will it bring it back up to normal mileage? Anyone had this ?
 

Rod

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Jan 12, 2018
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Location
Vacaville, CA, United States
But what were the symptoms of a bad sensor relay? Fuel mileage drop? Or just not properly reporting that the sensors were working correctly?
This was after installing a new motor on my 2001 TJ. I never check fuel mileage. My only indication was the 'check engine' code which referenced the O2 sensor heater circuit. Replaced the sensor...no change. Checked and replaced the relay....problem solved.
 

Mike the Silver TJ

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Jan 10, 2019
Messages
449
Location
Jacksonville FL
Lots of great information in this thread. Thanks to everyone who contributed. Several weeks ago I had a CEL P0431 Warm Up Catalyst Efficiency Bank 2 Below Threshold. It came on and off a couple of times over the weeks but the Jeep runs just fine. Very recently the CEL was flashing and the engine running rough for a few seconds after startup then cleared up. Had the CEL read again and they said it was the same code in there three times. I've scanned this thread pretty thoroughly and see that @Chris says this code usually means a bad CAT. My 2005 with stock exhaust has only 57,000 miles on it. I see other people in this thread with many many more miles before the CATs go bad. Not sure what to do at this point since it would seem odd to have a bad CAT with these miles. Since I had the CEL flashing I dont want to sit on it any more. How many miles were on your CATs when you had to replace them?
 
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Chris

Chris

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Lots of great information in this thread. Thanks to everyone who contributed. Several weeks ago I had a CEL P0431 Warm Up Catalyst Efficiency Bank 2 Below Threshold. It came on and off a couple of times over the weeks but the Jeep runs just fine. Very recently the CEL was flashing and the engine running rough for a few seconds after startup then cleared up. Had the CEL read again and they said it was the same code in there three times. I've scanned this thread pretty thoroughly and see that @Chris says this code usually means a bad CAT. My 2005 with stock exhaust has only 57,000 miles on it. I see other people in this thread with many many more miles before the CATs go bad. Not sure what to do at this point since it would seem odd to have a bad CAT with these miles. Since I had the CEL flashing I dont want to sit on it any more. How many miles were on your CATs when you had to replace them?
If you've replaced all the O2 sensors and that's not doing it, often times it's the cats.

When mine went bad at about 70k miles (remember, age counts just as well as milage) it had other symptoms though such as loss of power on the highway and at higher RPMs. I didn't know for sure the cats were bad, but since the symptoms pointed to it, I replaced them (it's only around $300 for replacement cats) anyways, and sure enough that did the trick.