Code 420 Converter Efficiency below threshold

Everyonce in a while the service engine soon light comes on and the code is 420. I have replaced the O2 sensor and it still shows up. Anyone have any idea what is wrong?

The catalytic converter can't have gone bad could it have?

How many miles are on your vehicle?

When DTC P0420 sets it means the oxygen storage capability of the CAT convertor is below efficiency, therefore, typically in most cases the sign of a flaky CAT convertor. Since the P0420 DTC sets the rear 02 sensor is doing it's job.

Probably over 100K miles on this the vans's second engine

Well I bet it is from the leaking intake manifold gasket. $700 repair if dealer does it. Guess I need to find an local shop.

local muffler shop will do it cheaper midas i seen on another forum quoted $225.00 for cat covertor replacement

Just to give everyone a final update. Bought the catalytic converter at Autozone for $80 something and a local muffler shop put it on for $30. No more code.

Thanks for the belated update. Due to the age of the thread and since the issue has come to a resolution this thread has been closed