S15/T15 Sonoma P/U 2WD L4-2.2L VIN 4 (1995)
Oxygen Sensor: Testing and Inspection
Diagnostic Trouble Code (DTC) 13 indicates an open in the Oxygen Sensor (O2S) circuit. DTC 44 indicates a low voltage in the O2S circuit.
DTC 45 indicates a high voltage in the 02S circuit. If a DTC is set, the engine will always run in the "Open Loop" mode. On heated oxygen
sensors value will drop lower towards 0 as the sensor heater inside the sensor warms up. Refer to Diagnostic Trouble Code Charts. Under
Computer and Controls/System Diagnosis/Procedures. See: Testing and Inspection
Normal scan voltage varies between 100 mV to 999 mV (0.1 and 1.0 volt) while in "Closed Loop." DTC 13 sets in one minute if voltage remains
between 0.35 and 0.55 volt, but the system will go "Open Loop" in about 15 seconds.
Using the scan tool, observe the long term fuel trim values at different RPM and air flow conditions to determine when DTC 44 or DTC 45 may
have been set. If the condition for DTC 44 exists, the long term fuel trim values will be around 150. If the condition for DTC 45 exists, the long
term fuel trim values will be around 115.
