Oxygen Sensor: Testing and Inspection

The "Scan" has several positions that will indicate the state of Oxygen Sensor (O2) voltage, integrator, and block learn. A problem in the O2 sensor circuit or fuel system, should set a Code 13 (open circuit), Code 44 (lean indication), Code 45 (rich indication), or Code 61 degraded, or contaminated O2 sensor. Refer to System Diagnosis / Diagnostic Charts / Diagnostic Trouble Code Charts if any of these codes were stored in memory.