Heated Oxygen Sensor (Ho2S): Notes
WARNING: This page is about a different car, the 2005 Hyundai Accent and 2004 Hyundai Accent. However, it is still accessible from the selected car via links, so may be relevant.
The heated oxygen sensor senses the oxygen concentration in the exhaust gas, then converts it into a voltage and then sends this to the ECM. The heated oxygen sensor gives an output of about 800mV when the air fuel ratio is richer than the theoretical ratio and output of about 100mV when the ratio is leaner (higher oxygen concentration in exhaust gas.) The ECM controls fuel injection based on this signal so that the air fuel ratio is maintained at the theoretical ratio.