It's been a few weeks and several hundred miles, then today it warmed up to upper 50's with rain (from -20 last week). CEL came back on tonight, darn it! I suspect a bad ground and plan to clean all the grounds to see if that does it.

 

Have you checked your voltage? My CEL came back on but my voltage is not the straight 1V like it should be if the sensor wasn't reading... I am curious t see other people's thoughts on this!

 

Mine was having the same problem when I started this thread. I think all my posts are on here but I'll sum up.
I cleaned and checked all connections. Light was off for a week. Replaced sensor (even though it bench tested ok) light was off for a month then cam back on. Bit the bullet and ordered the APN manni everyone talks about on here and took off the intake to inspect exhaust manni. It was cracked in three places. Did the swap for the APN and I have to say I like it just as much as all the other guys! Thanks everyone @ cherokeeforum for putting me on to it! After that and a code reset I have never had the code back. Been over 2,000 mi. and 8 mo. Here is a video of the swap I did if you want an idea of what you may be up against:

 

J20.... what an awesome video! Man I wish my rig looked as nice as yours. Unfortunately, many of my under-hood components are very rusty. My fuel rail, PS hose fittings, even my valve cover is rusty, which is why I think bad grounds could be my issue. Also the fact that I went from just the P0138 before DS O2 sensor change to that again plus the P0455 in just a week leads me to suspect electrical issues. My EM sounds OK and I don't smell exhaust or fuel. I hope that's the case... the EM swap looks like a heck of a project!

Thanks tons for sharing your knowledge! Will post updates as I go.

~Cheers!

 

I have not checked the voltage... not even sure how, though I believe I did see a post here somewhere on how to do that. I will research that...thanks for the suggestion.

 

That's crazy, your cherokee must have lived on the coast with a PO. It might be possible you just have a vacuum leak. You can get a pvc pipe and hold it to your ear listening all around the engine, while running, to listen for the hiss of a leak. Listen close to that manni too for a "pft pft pft" from an exhaust leak. Mine did not smell, but I could hear it.
It sounds like Outburst is talking about testing the leads from the o2 sensor after the engine is warm. It puts out close to 1v when hot.
Thanks for your comment about the vid.

 

Well the vehicle is a local Jeep... one owner prior to me. This ain't the beach, but we use TONS of road salt. The strange thing is that the body is in good shape, but as I've said many of the underhood components (plated fittings in particular) are rusty. Will probably need to replace hoses, fuel lines Etc soon.

Listened carefully to my exhaust today... sounds ok to me. Then I took a good look at it under the intake...it's new! This was quite a nice revelation. I ordered an OBDII scanner the other day so that when my CEL comes back on I'll be able to read it without pestering my local mechanic. As soon as I get some time, I will refresh all the grounds and post the results. Again thanks for sharing your knowledge!

 

Ik this thread is super old but it’s offered a good value of information, I have a 2000 Cherokee Sport With fed Emissions. I’ve recently stumbled across the p0138 , after a fair amount of research I haven’t been able to find the part numbers to the only 2 oxygen sensors I have upstream and downstream, if anyone has them it would be a lifesaver. It runs fine , thank you for your guys time !

 

P0138 usually means a failed Cat

(it could be sensor or wiring)

Use OBD2 live data to check

Download Parts manual for your model

That will have the correct OEM part numbers, which can then be x-ref at Rock Auto or eBay

Its my understanding front and rear sensors are the same, although part number may differ dure to connector, measures 0-1V

P0138 is generated when the PCM senses a discrepancy between the front/rear sensors, as I said, due to worn out or failed cat, how old are they ?, the vital minerals deplete over time

I have purchased cheap Chinese O2 sensors, they are junk, a used OEM is more reliable