Circuit Description

WARNING: This page is about a different car, the 2002 Oldsmobile Intrigue and 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.

Heated Oxygen Sensors (HO2S) are used to minimize the amount of time required for Closed Loop fuel control operation and to allow accurate catalyst monitoring. The oxygen sensor heater greatly decreases the amount of time required for fuel control sensor HO2S 1 to become active. The oxygen sensor heater is required by catalyst monitor sensor HO2S 2 to maintain a sufficiently high temperature. This allows accurate exhaust oxygen content readings at an increased distance from the engine.

The Powertrain Control Module (PCM) will run the heater test only after a cold start, which is determined by the engine coolant temperature and the intake air temperature at the time of start-up. The heater test will also run only once during an ignition cycle. When engine is started, PCM will monitor HO2S voltage. When HO2S voltage indicates that the sensor is sufficiently active, the PCM determines how much time has elapsed since start-up. If PCM determines that too much time was required for HO2S 2 to become active, DTC will set. The appropriate length of time for the HO2S to reach operating temperature is calculated based on the engine coolant temperature at start-up and the average mass air flow since start-up. The more total airflow and the higher the start-up engine coolant temperature, the less time should be required for HO2S activity.