2015 JKU P0420

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WaterHead

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May 7, 2022
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Location
Birmingham, AL
2015 JKU Rubicon - @75k Miles

Could use some help on P0420 Code

Had a P0052 02 Sensor 2/1 couple weeks ago and replaced all 4 O2 sensors, cleared all codes and ran good for about a week.

Friday the CEL came on and scanner showed P0420 (Bank1). Seems to be running good otherwise. Checked for any exhaust leaks and could see/hear any. Attached are screenshots of both Bank 1 and Bank 2.

Questions, should I not worry with chasing down a short or open circuit since I'm getting a voltage ready on all 4 sensors?

Based on my knowledge, the Bank 1 cat is not working. Should I just replace? Seems like replacing the cat is just a band-aid fix with only 75k miles on?

Thought about running some Seafoam through and see if that cleans things up.

Currently have battery disconnected to see if I can get all the codes (temporary and permanent) to clear and if they come back on for 3rd time.

Jeep Code 01.jpg


Jeep Code 02.jpg


Jeep Code 03.jpg
 
Replacing the cat is pretty much always a Band-Aid. Because cats don't really fail. They're killed by something. So unless you figure out what killed it, you're likely to end up with another dead cat. Most cats fail for one of three reasons:
1 - Overheating from misfires, poor AFR, excessive load, etc.
2 - Fouling from burning oil, excessive carbon buildup, or internal coolant leaks.
3 - Physical destruction, from banging it on something. Like a big rock.
 
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Dirty Dog said:
Replacing the cat is pretty much always a Band-Aid. Because cats don't really fail. They're killed by something. So unless you figure out what killed it, you're likely to end up with another dead cat. Most cats fail for one of three reasons:
1 - Overheating from misfires, poor AFR, excessive load, etc.
2 - Fouling from burning oil, excessive carbon buildup, or internal coolant leaks.
3 - Physical destruction, from banging it on something. Like a big rock.
Click to expand...
Thanks! That's what I was thinking if I were to change out the cat it would only be a band-aid

Going through your points:
1 - based on the scan above, it doesn't seem to be an AFR issue. No smell out exhaust. Not noticing a misfire but I need to check this again
2 - just changed oil, it was relatively clean. Nothing stood out. Coolant seems to be good as well
3 - no off pavement driving in last 6 months, and where the cats are located I would assume there would be more damage than just to the cat.

If the code is just "Permanent" should I just ignore it and see if the CEL comes back? I'm having issues with that thinking though b/c of the graph for Bank 1.
 
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WaterHead said:
Thanks! That's what I was thinking if I were to change out the cat it would only be a band-aid

Going through your points:
1 - based on the scan above, it doesn't seem to be an AFR issue. No smell out exhaust. Not noticing a misfire but I need to check this again
2 - just changed oil, it was relatively clean. Nothing stood out. Coolant seems to be good as well
3 - no off pavement driving in last 6 months, and where the cats are located I would assume there would be more damage than just to the cat.

If the code is just "Permanent" should I just ignore it and see if the CEL comes back? I'm having issues with that thinking though b/c of the graph for Bank 1.
Click to expand...
Permanent codes stay until the computer decides the condition no longer applies. That could require a certain number of cold starts, or a certain number of miles, or whatever. If you have a permanent code and no current or pending codes, then I wouldn't worry about it. I'd drive it for a week or two and then rescan it to see if the permanent code has cleared.
 
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Dirty Dog said:
Permanent codes stay until the computer decides the condition no longer applies. That could require a certain number of cold starts, or a certain number of miles, or whatever. If you have a permanent code and no current or pending codes, then I wouldn't worry about it. I'd drive it for a week or two and then rescan it to see if the permanent code has cleared.
Click to expand...
Thanks again! That’s what I’m leaning towards. Guess I’m just having a hard time bc the bank 1 o2 downstream sensor is still bouncing like upstream.

Even thought about swapping the O2 sensor to the bank 2 side to see if the problem is still on bank 1 or not. But those things aren’t easy to get to.

Man I miss my 1990 Blazer with and 350!!!
 
Downstream sensors shouldn’t bounce like the upstream for sure. If the cel light is pissin u off like it does me, slap some O2 spacers on it if you don’t have to deal with emissions testing. Code doesn’t necessarily mean cat is bad. Just under the threshold of what the pcm thinks it should be. Good luck🍺🍺
 
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BigAL07 said:
Downstream sensors shouldn’t bounce like the upstream for sure. If the cel light is pissin u off like it does me, slap some O2 spacers on it if you don’t have to deal with emissions testing. Code doesn’t necessarily mean cat is bad. Just under the threshold of what the pcm thinks it should be. Good luck🍺🍺
Click to expand...
That’s what I’m thinking. I’ll probably just give a couple days or two. The CEL is currently off, just my OCD killing me knowing the graph is bouncing when it shouldn’t.
 
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About to pull my hair, at least the little bit left!!! Maybe I'm overthinking but knowing the graph looks the way it does.

Gas tank was about at 1/4 so topped off with high octane and added Seafoam to see if it would clean things up. Before I did that I check the scanner one last time and the "permanent" code is still there and not there is a "pending" code. Still same P0420.

Probably going to give it a few days then still there I think I'll run it by a shop.
 
WaterHead said:
About to pull my hair, at least the little bit left!!! Maybe I'm overthinking but knowing the graph looks the way it does.

Gas tank was about at 1/4 so topped off with high octane and added Seafoam to see if it would clean things up. Before I did that I check the scanner one last time and the "permanent" code is still there and not there is a "pending" code. Still same P0420.

Probably going to give it a few days then still there I think I'll run it by a shop.
Click to expand...

Take it out somewhere and run it hard.
 
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WaterHead said:
Gas tank was about at 1/4 so topped off with high octane
Click to expand...
That won't do anything at all.
WaterHead said:
and added Seafoam to see if it would clean things up. Before I did that I check the scanner one last time and the "permanent" code is still there and not there is a "pending" code. Still same P0420.
Click to expand...
So you've got a permanent code but no pending. Sounds fixed. Now you just need to give it time to clear.
 
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And the Saga continues. Went out and ran some errands. No CEL but still had the permanent and pending code but the graph for Bank 1 was looking better. The Sensor 2 wasn't mirroring Sensor 1 nearly as much.

Took long way everywhere with hills to really get the rpm's up. Thought maybe things were getting fixed!!!

1/2 mile from home the CEL came back on and now have the P0420 pending, stored and permanent!! And graph for Bank 1 is back to identical for Sensor 1 and 2.

Really thinking of running by the shop and let them have it for awhile since the codes are all back.

Thoughts?
 
WaterHead said:
And the Saga continues. Went out and ran some errands. No CEL but still had the permanent and pending code but the graph for Bank 1 was looking better. The Sensor 2 wasn't mirroring Sensor 1 nearly as much.

Took long way everywhere with hills to really get the rpm's up. Thought maybe things were getting fixed!!!

1/2 mile from home the CEL came back on and now have the P0420 pending, stored and permanent!! And graph for Bank 1 is back to identical for Sensor 1 and 2.

Really thinking of running by the shop and let them have it for awhile since the codes are all back.

Thoughts?
Click to expand...

So how does it run now since the CEL is back on?
 
Seems to be running fine. No lag or anything. Glancing through all the live data on scanner, everything else seems to be fine. Temp on both cats are almost identical as well.
 
WaterHead said:
Seems to be running fine. No lag or anything. Glancing through all the live data on scanner, everything else seems to be fine. Temp on both cats are almost identical as well.
Click to expand...

Is that the Downstream one setting it off?
 
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