I had this last week with mine. Had both cats replaced then a day later the light came on. Diagnostic stated the post cat sensor bank 2 was at fault and indicated the cat was defective. After clearing the fault and cleaning the sensor plug contacts its not returned. I also checked for gasket leaks on the cat but found nothing. Now my light came on when the car was rather hot after a long journey nor when first starting out.
The old cats were original and had done 80k miles but we're still functioning ok. I replaced them with some mint clean 35k jobs.Im hoping the contact clean has done the trick regarding the management light.