Heated Oxygen Sensor (HO2S 2) Testing

A problem with the HO2S 2 electrical circuits should set Diagnostic Trouble Code (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 [prime ]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 HO2S Insufficient Activity Bank 1 Sensor 2 or DTC P0420 TWC System Low Efficiency Bank 1. Refer to System Diagnosis / Diagnostic Tables for testing information. Testing and Inspection