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Heated Oxygen Sensor (HO2S 2) Catalyst Monitor Testing
A problem with the
HO2S 2 electrical circuits should set DTC P0137, P0138 or P0140, depending on the specific condition. If the catalyst is functioning correctly, the HO2S 2 signal will be far less active than that produced by HO2S 1. If a problem exists which causes the VCM to detect excessive HO2S 2 activity outside of an acceptable range for an extended period of time, the VCM will set DTC P0420, indicating that the three-way catalytic converter's oxygen storage capacity is below a threshold considered acceptable. Refer to
DTC P0137 HO2S Circuit Low Voltage Bank 1 Sensor 2 or DTC P0138 HO2S Circuit High Voltage Bank 1 Sensor 2 or DTC P0140 H02S Insufficient Activity Bank 1 Sensor 2 or DTC P0420 TWC System Low Efficiency Bank 1.