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Definition of P0420 is catalyst below threshold. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). Catalytic converters are not normally a "wear" type item, that is they are not deisgned to wear out and need replacement. If they have failed, it is likely due to something else that caused it to fail.
P0447 Evaporative Emission Control System Vent Valve/Solenoid Circuit Open. The Powertrain Control Module (PCM) has detected an open within the circuit that controls the vent valve or solenoid for evaporative emission systems vapor.
Read more at: http://www.obd-codes.com/p0447