Oxygen Sensor: Testing and Inspection

The Oxygen Sensor if open, should set a Diagnostic Trouble Code (DTC) 13. A constant low voltage in the sensor circuit should set a DTC 44. A constant high voltage in the circuit should set a DTC 45. DTCs 44 and 45 could also be set as a result of fuel system problems. See DTC charts for conditions that can cause a lean or rich system. Testing and Inspection