Circuit Description

WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

Heating elements inside the heated oxygen sensor (HO2S) minimize the time required for the sensors to reach operating temperature and to provide an accurate voltage signal. A low side driver within the powertrain control module (PCM) is pulse width controlled to provide current to the heater elements. During warm-up, the PCM will pulse the heaters ON-OFF to prevent thermal shock to the sensor components from moisture in the exhaust system. The PCM will not allow continuous HO2S heating until calibrated limits of time, temperature, and intake airflow have been reached. The PCM continuously monitors the HO2S heater current draw and operating state by briefly turning OFF the heater low side driver at regular intervals. The PCM calculates the HO2S heater element resistance based on the actual heater current. If the PCM detects that the HO2S heater element resistance is too high, this DTC will set.

Each HO2S heater has the following circuits:

HO2S heater ignition 1 voltage
HO2S heater low control