Eighty-Eight Royale FWD V6-3.8L VIN K (1996)
Heated Oxygen Sensor: Testing and Inspection
Heated Oxygen Sensor 2 (HO2S 2) Catalyst Monitor
The HO2S 2 sensor produces an output signal which indicates the oxygen storage capacity of the catalyst; this in turn indicates the catalyst's ability to
convert exhaust gases efficiently. If the catalyst is operating efficiently, the HO2S 1 signal will be far more active than that produced by the HO2S 2
sensor. The catalyst monitor sensors operate the same as the fuel control sensors.
Although the HO2S 2 sensors 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 monitoring.
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.
