DM6156

I've had an intermittent P0430 on my 08 JKU. It currently has 142k miles.

I had mechanic do smoke test on exhaust, found no leaks and they noticed issue with rear 02 sensor and changed it.
P0430 came back so i had exhaust shop replace cat (replaced both small ones with larger one).
After driving a few days to get ready monitor on to take it to get emission done, the P0430 came back.

I've seen many complaints using search of P0430 and most were resolved with either new cat or new O2 sensor. This has not resolved issue for me and I've got to get this resolved within the next couple weeks so i can get emission test done to get new tag.
Anyone seen similar and found a different cause than cat and O2 sensor?

From my limited understanding and research, seems like the causes can be:
bad front O2 sensor
bad rear O2 sensor (already replaced)
exhaust leak (not likely since new cat was installed and was welded, not clamped).
bad cat (not likely since new one was just installed a few days ago - shop said they do bunch of jeeps and always replace both small with a larger one).
wiring issue with either front O2, rear O2 or both

any other possibilities I'm missing?

exhaust shop said they see replacing the cat 90% of the time fixes P0430 on jeeps and mentioned they thought could be wiring issue with other 10%, but were not sure as they only do exhaust work.

any help is appreciated.

Mark Doiron

I had this code and it was fixed by replacing the four (yes, there are four in one assembly) catalytic converters. If I was in your position, the first thing I'd do before trying to chase down wiring or such would be to put an OEM cat in there. Not saying that will fix it, but am saying that you really can't be sure where you're at based on the word of an exhaust shop mechanic who performed an unapproved mod to the emission control system on your Jeep.

DM6156

UPDATE:

my mechanic performed a smoke test and was able to find a leak in the weld of the new cat.
the exhaust shop has the jeep today to fix the weld.

my mechanic also did indiate the front O2 sensor was switching slower in comparison to the other side front, for $30 part, I opted to have him replace it (believe it was original to vehicle).

I'll post update after i hear back from exhaust shop - my mechanic thinks the exhaust leak was the issue.

Mark Doiron

When I was having this code I was past 200K miles, so the mechanic (a pro, but also a personal friend) recommended change all four--lest I be back in the next six months with the same code. It ended up not fixing the issue until we replaced the catalytic converter assembly. Good luck, hope that it works out for you!

karls10jk

How much was the cat assembly Mark? I know the factory piece to include the crossover is roundabouts $1200

Mark Doiron

It was about $650, but I have access through a friend to better prices on parts through the local distributor for all dealers (they handle virtually all vehicle makes). It looks like Quadratec has a "factory replacement part") for about $600 ...

https://www.quadratec.com/p/walker-e...kaAkbzEALw_wcB

DM6156

The exhaust shop fixed the weld, no more leaks and that resolved my issue too. On the same day i picked up the jeep, i scanned for ready monitor and was good. On the next day, I passed emissions. As of today, no more codes and it does seem to run (especially at idle) better.

To toss this out, was $300 for the new larger cat and pipe work for one side so that it would around $600 for both (what Mark mentioned). The shop told me it woud take about 2 hours labor per side.