Skylark V6-3100 3.1L VIN M SFI (1996)
Oxygen Sensor: Description and Operation
Catalyst Monitor Oxygen Sensors
The catalyst monitor sensors operate the same as the fuel control sensors. Although the HO2S 2 sensors [prime] main function is catalyst
monitoring, it also plays a limited role in fuel control. If the sensor output indicates a voltage either above or below the 450 millivolt bias voltage
for an extended period of time, the PCM will make a slight adjustment to fuel trim to ensure that fuel delivery is correct for catalyst monitonng.
A problem with the HO2S 2 signal circuit should set DTC P0137, P0138 or P0140, depending on the specific condition. A fault in the heated
oxygen sensor heater element or its ignition feed or ground will result in slower oxygen sensor response. This may cause erroneous Catalyst
monitor diagnostic results. A fault in the HO2S 2 heater circuit should cause DTC P0141 to set.
