Catalytic Converter: Testing and Inspection

(_P0420_)
- The scan tool indicates Diagnostic Trouble Code (DTC) P0420: Rear Catalyst system efficiency below threshold.
(_P0430_)
- The scan tool indicates Diagnostic Trouble Code (DTC) PO43O: Front Catalyst system efficiency below threshold.

NOTE:
- If some of the DTCs listed below are stored at the same time as DTC PO42O and/or PO43O troubleshoot those DTCs first, then troubleshoot DTC PO42O and/or P0430.

P0137-9: Rear Secondary HO2S (Bank 1, Sensor 2)
PO141 : Rear Secondary HO2S Heater (Bank 1, Sensor 2)
P0157-9: Front Secondary HO2S (Bank 2, Sensor 2)
PO161 : Front Secondary HO2S Heater (Bank 2, Sensor 2)

Possible Cause
- Front TWC or Rear TWC Deterioration
- Leakage in exhaust system