Theory Of Operation

The Oxygen Sensor is equipped with a galvanic battery that typically generates a voltage signal between 0.0 volts and 1.0 volts. The O2 Sensor also includes a heating element that keeps the sensor at proper operating temperature during all operating modes. Maintaining correct sensor temperature at all times allows the system to enter into closed loop operation sooner. The heater temperature is inferred from the heater element resistance. A self-learning procedure exists to account for normal part to part variation and aged components. This improves the accuracy of the temperature inference. When the diagnostic is enabled, the sensor temperature is checked to ensure it is within an acceptable range. If it is not, a fault is detected.