Heated Oxygen Sensor
WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 2002 Mazda Tribute, 2002 Mazda Protege5, 2002 Mazda Protege, 2002 Mazda Millenia, and 2002 Mazda MX-5 Miata. However, it is still accessible from the selected car via links, so may be relevant.
At normal operating temperature, the Heated Oxygen Sensor (HO2S) monitors oxygen content of exhaust gases. A heating element is used to warm the HO2S to operating temperature, enabling faster conversion of the feedback system to closed loop operation.
The HO2S produces low voltage (less than 0.4 volt) to indicate a lean mixture (high amount of oxygen) and a high voltage (more than 0.6 volt) to indicate a rich mixture (low amount of oxygen). This voltage signal is transmitted to the PCM. All models use more than one sensor.