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Catalyst monitor is never ready for smog test: could it be due to some other failure such as:

a bad catalyst converter?

or Catalyst monitor has been disabled??

or a bad Catalyst monitor ???

If you have a code post it here, along with what car, miles, and age.

Your oxygen sensor and oxygen sensor heater monitors must have run and passed before the catalytic converter monitor will run.
Have they all run to completion and passed?

If you don’t have a code, most parts stores will read them for you for free.