Downstream O2 Sensor Help

[gdufour11]

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!

[RCP Phx]

The first thing I would look at is the wiring and it's a special twisted pair.

[Saudade]

Yeah, check the harness and make sure it's not rubbed through somewhere.

Any running issues? Do you have any freeze frame data?

[Tim_MN]

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

[gdufour11]

What should I be reading voltage wise from the vehicle across the heater terminals? What about the O2 sensor?


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[gdufour11]

This screen shot is from this morning.



Last night it was reading .4 V on o2 bank1 sensor 2


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[emx721]

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.

[lawsoncl]

Originally Posted by gdufour11

What should I be reading voltage wise from the vehicle across the heater terminals?

Pretty sure it's 12-volts to the heater