HO2S Sen. 2

Scan tool range 0 to 1132 mV. Represents the catalyst monitor exhaust oxygen sensor output voltage. If the catalyst is operating efficiently, the HO2S 1 signal will be far more active than that produced by the HO2S 2 sensor. If the PCM detects a level of HO2S 2 activity that indicates the catalyst is no longer operating efficiently, DTC P0420 will be set.