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Downstream O2 Sensor Help

gdufour11

NAXJA Forum User
ownstream O2 Sensor Help!

All,

I cannot pass the DEQ emissions test because I cannot seem to keep my O2 sensor working for more than 1 day. I have replaced my O2 sensor, twice now and get the same results. I get a P0138 code. I have a 2000 Jeep Cherokee Classic 4WD, XJ.

Initially, after replacing the sensor, everything is running fine, I get a reading of 0.4-0.42 V from the Bank 1 Sensor 2, then all of the sudden it will start reading 1V and then throws the code. It seems like then sensor works for a couple of hours of running then just gets cooked! The last one I used was a Bosch sensor. I don't know what else, the wiring seems fine and I would assume is good because I get a decent reading for a while before it fails.

Is it possible my PCM is just bad?

I hate to dump a bunch of money into this thing, just want to keep it going for a few more years!:wow:
 
The first thing I would look at is the wiring and it's a special twisted pair.
 
Yeah, check the harness and make sure it's not rubbed through somewhere.

Any running issues? Do you have any freeze frame data?
 
Wiring issues are much more common and much more likely than PCM issues.


P0138 JEEP - O2 Sensor 1/2 Circuit High

P0138 JEEP Possible Causes
•Faulty Rear Heated Oxygen Sensor Bank 1
•Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
•Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
•Intake air leaks
•Exhaust gas leaks
 
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What should I be reading voltage wise from the vehicle across the heater terminals? What about the O2 sensor?


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I had almost the exact same issue, I can almost guarantee the wiring got destroyed by the drive shaft. Follow the harness wiring and you'll see the wires got rubbed out and is sitting on the driveshaft. I put them together with wire butt connectors and all is good now.
 
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