Fuel Management - Mazda

In 2010 I replaced the catalytic converter (2002 Mazda Protege). Now (Mazda dealership) says the code is to replace it again.
I went to an independent mechanic and he says the code is for fuel management.
So, what is fuel management and what is the approximate cost?
Thank you.
Katy25

If your engine is running a rich fuel mixture, it can damage the cat converter.

Thank you.

You need to get the exact and specific code in the format “P1234” and post it. Also report anything of symptoms you notice, if any, and something of the car’s maintenance history - beyond empty statements like “well maintained” or “regular oil changes.” Get specific.

Fuel management isn’t “a” thing - its a whole big system of things.

OK

Its is MOST likley bad O2 sensor or Seonsors… It would be very strange for a cat to go that quickly unless the car was runnig very poorly