P0420--Catalytic Converter Efficiency Below Threshold:
leak in exhaust system
Air/Fuel Sensor, Bank 1 Sensor 1
Heated Oxygen Sensor Bank 1 Sensor 2
Catalytic Converter defective
DIAGNOSIS -- with scanner, performing recommended tests to isolate cause.
The ECM observes the waveform of the oxygen sensor located behind the catalyst to determine whether the catalyst performance has deteriorated.
If the catalyst is functioning normally, the waveform of the heated oxygen sensor located behind the catalyst switches back and forth between rich and lean much more slowly.
When the waveform of the heated oxygen sensor located behind the catalyst alternates frequently between rich and lean, it indicates that catalyst performance has deteriorated.
* Bank 1 refers to the bank that includes cylinder No.1.
* Bank 2 refers to the bank that does not include cylinder No.1.
* Sensor 1 refers to the sensor closest to the engine assembly.
* Sensor 2 refers to the sensor farthest away from the engine assembly.