Check engine light is on po404 po405e

Question

I have a 2001 chevy impala ls I have aengine code po404 po405 I have replaced egr and the cat im not sure what it could be it,it does have a ruff idle and dies sometimes on low idle

Answer 1

P0404 Exhaust Gas Recirculation (EGR) circuit range / performance

P0405 Exhaust  Gas Recirculation (EGR) Sensor A circuit low

The EGR pintle can still be taking up debris You can do a top engine clean or a fuel injector inductive cleaning with a MAF (mass airlflow) cleaning and do a throttle body cleaning.