ISX15 - CM2350 - DOC Leak - Next Steps?

[JimT]

Maybe Rawze has more experience/knowledge to share, but my guess is if it's leaking it's likely due to the higher exhaust pressure. Could be at the end of it's functional life and the catalyst is no longer sufficient leading to DPF and DOC clogging up and creating higher pressures. Could also be face plugging on the DOC causing higher pressures, however I think you would have noticed that when it was removed/inspected. A good welder might be able to reseal it, but something caused the leak to form and my money is on

MY OPINION is that, assuming they are the same age, if the DOC needs to be replaced then the DPF is likely to be in the same situation. From what I've seen it appears they typically need replacing somewhere in the 400,000-600,000 mile range depending on maintenance and abuse history.

As to your numbered questions:
1 - Hard to see, but probably.
2 - Go with an OEM option for proper performance
3 - By the time codes pop up something is really wrong.
4 - If the DOC is leaking then it's throwing ALL the sensor reading off. Restrictions are higher then they seem since some of the pressure is being relieved by the leak. Calculations by the ECM are based on inaccurate data and therefore not optimal, at best.