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Discussion Starter #1
Hey guys-

I have an 02 Jeep Wrangler X that has had "check engine" light problems for a while now. The code that is showing now is:

P0142
O2 Sensor Circuit Malfunction (Bank 1 Sensor 3)

Which oxygen sensor is this? Can I just replace that O2 sensor and the problem will be fixed?

If you could tell me where this sensor is located and how to fix this, I'd greatly appreciate it. Thanks!!!
 

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I know this issue has come up before, and there are some very good technical guys on this forum. As far as I know, there is a sensor on your manifold, and one on your catalytic convertor. Which one is which, I am not sure. Be patient, and someone with more knowledge on this should jump in here and help you with this. Sorry I am not that familiar with the O2 sensors.
 

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bank 1 is referring to the sensors before the cat, i believe. and i think you have two that are right after the little mini-cats, then one before and one after the cat. sensor 3 should be the third o2 sensor in the line. i have a 2.5, so i'm not 100% on that, but i think that's how it all works.
 

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just crawl up under you jeep. look on the drivers side of the engine and follow the exhaust manifold from the block. there should be two pipes and then each pipe will have a bulge in it. just after each bulge is an o2 sensor(easily spotted by the wires coming from it). keep following the pipe. after the two pipes come together to make 1, there might be another sensor shortly thereafter. and then the last one would be after your cat. there are sockets and such to take an o2 sensor out, but a good set of channel locks work just as well. simply take it out, unplug it, screw the new one back and and then plug it up. should be good to go after that.
 

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Discussion Starter #10
I don't want to have to replace them all if they don't need it but at the same time I don't want to take it in to the dealer and get ripped off!!
 

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02 Sensor

AggieChris said:
Hey guys-

I have an 02 Jeep Wrangler X that has had "check engine" light problems for a while now. The code that is showing now is:

P0142
O2 Sensor Circuit Malfunction (Bank 1 Sensor 3)

Which oxygen sensor is this? Can I just replace that O2 sensor and the problem will be fixed?

If you could tell me where this sensor is located and how to fix this, I'd greatly appreciate it. Thanks!!!
I have done some research for you. Bank 1 is pre CAT. Bank 2 is post CAT. Without knowing the size of your engine, it is hard to know how many sensors you have. I saw two of them from the under side of our 04, just past the manifold. After doing some extensive reading, it appears that there could be multiple reasons for this code. Check the wiring to make sure that none of them are loose, or detached. Also, without knowing the mileage on your Jeep, it could also be caused by a malfunctioning CAT converter. This would tend to give you a bad reading on bank 2, I would think. Here is one of the sites that I went too, that might help you identify the sensor you need. http://www.automedicsupply.com/index.php?ref=Google&stopredirect=yes&width=800&height=600 Without actually replacing them for you, and seeing the result, it is hard to know what else to do for you. Another idea is to call a dealership near you, and ask them to interpret the code for you. Tell them to isolate the exact sensor that needs to be replaced. They will also tell you how to cancel out the code after you replace the sensor.
 

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Great advice

khenderson said:
bank 1 is referring to the sensors before the cat, i believe. and i think you have two that are right after the little mini-cats, then one before and one after the cat. sensor 3 should be the third o2 sensor in the line. i have a 2.5, so i'm not 100% on that, but i think that's how it all works.
This all makes very good sense, and is very logical. I wasn't sure of his engine size, but it is reasonable to say that sensor 3, should be the 3rd sensor in line. So it should be the sensor just before your catalytic converter.
 

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Discussion Starter #14
Thanks guys!! I have a 4.0L V6 engine and about 48K miles right now. If you need any other specifics, just let me know. Sorry I didn't post those in the original post.

I was looking under the hood and under the Jeep for the oxygen sensors and I see the 2 that come out of the manifold before the cat converter. There were 2 closer to the engine and then another 2 further down but still before the cat. I believe there is one after the cat.
 

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Discussion Starter #15
Based on my engine size do you know how many sensors I SHOULD have? I am going to check the wiring on them today and see if that does anything.
 

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I should mention one more thing from what I read. This is for all of you that like to play submariner with your Jeeps. As you can imagine, your exhaust runs very hot, and your CAT gets extremely hot........hot enough to cause grass fires on lower vehicles.........so what happens when you put something very hot, into cold water..........I know, I know......you get steam.....lol.........but worse than that, you crack the inner elements of your Catalytic convertor..........hmmmmmmm.....lets see now, would that cause problems with the sensors? The answer of course, is YES, IT DOES. That is the number one cause for problems with your exhaust system. As they say on Ribley's, believe it or not.
 
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