My new to me 2010 Jeep Wrangler (3.8L) has 120k miles. Both P0420 and P0430 came on, indicating that the cats on both banks are not functioning.

I first checked that the O2 sensors had readings using a bluetooth OBD2 reader. They show readings and seem to be functioning.

Then I noticed that each side of the engine has 1 broken bolt on the exhaust manifold. I read online that an exhaust leak could cause issues so I paid an exhaust shop to extract those bolts, but they were only able to extract 1 of them. I cleared the ECU codes and drove around for a while and both P0420 and P0430 came back. Since one side has all the bolts, that tells me a leak isn’t causing the issue.

I bought O2 spacers online to see if that makes the codes go away. After installing the spacers on the rear O2 sensors and driving around till the Catalyst test on the ECU completed, the codes did not come back. Does that rule out O2 sensors having issues?

Does that confirm that cats on both sides of the engine went bad? What are the chances of both sides failing like that at the same time? ugh… going to be an expensive repair if its the cats.

  • rblair63@alien.topBEnglish
    1·
    1 year ago

    Good possibility that the exhaust leak at the manifolds caused a perceived lean condition so the pcm was adding extra fuel to compensate which would mean dumping fuel into the cats ruining them slowly over time

  • Alex427z@alien.topBEnglish
    1·
    1 year ago

    99.99% of the time, P0420 and P0430 codes will need the converters replaced to fix it. It is strange they both set codes at the same time but thats what I’ve seen.

  • waynep712222@alien.topBEnglish
    1·
    1 year ago

    with your blue tooth… see if you can get into live data and then graphing mode…

    look at the upstream oxygen sensors first… O2B1S1 voltage and O2B2S1 voltage in graph mode.

    bring the RPMs to steady throttle 2500 RPM… do you get a nice clean wave form in both… then slow to idle over 10 or 15 seconds… do you still have a nice waveform… if not… you need to figure out why… air intake leaks… vacuum leaks… misfiring… exhaust leaks before the upstream oxygen sensors…

    if you get good upstream waveforms… look at the down stream sensor voltages again at 2500… steady pedal…

    do you have a 0.6 to 0.7 volt reading or reduced waveform voltage compared to the upstream… then your cats are reducing emissions…

    P0420 and P0430 are the downstream sensors are not showing a reduction in emissions…

    if the upstream components are not working properly… you can and will get the dreaded P0420, P0430 codes… indicates that the catalytic converter isn’t functioning efficiently . cats are passive… Garbage in garbage out…