C 2500 Truck 2WD V8-5.7L VIN R (1997)
Oxygen Sensor: Testing and Inspection
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.
