reasons for catalytic converter failure

What is your question?

my car has a p0420 code, check engine light is on solid, Replaced the canister purge valve, sparks plugs and ignition coil. check engine light came back on. took it to a shop and was told all sensor were good, I have a coolant leak, and when driving the car the engine sounds low and louder with rattling sound.

What makes this problem better or worse?

fast gas pedal

How long has your 2016 Chevrolet Sonic had this problem?

about 2 months