How do I know if it needs both sides or one side for the catalytic converter? on 2006 Dodge Magnum

This car has a 2.7 L V6 engine. I have not been smelling the rotten egg smell. the engine light came on and i took it in to havce it checked and was told the engine was all carboned up. That it needed a new catalytic converter. needed to have the engine cleaned out and needed new plugs.

Asked by for the 2006 Dodge Magnum
The catalytic converter in your car should be covered by an 8 years/80K miles federal emission warranty.
Do you have the diagnostic trouble codes? It would indicate the failed cat. converter.

2 more answers
All newer vehicle including your Magnum will set the "Check Engine Lite " on with a diagnostic code for catalytic Converter effienency if the computer detects that it is not performing properly. This is done by the O2 sensors (downstream) behind the converter. The Powertrain Control Module (PCM) has the pre-programed voltage parameters for a catalytic Converter in Good condition. When the voltage from the O2 sensor is out of range, it means the catalytic Converter is starting to fail.
have your egr checked