Circuit Description

The heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by the ignition 1 voltage circuit through a fuse. Ground is provided to the heater on the low control circuit by a low side driver within the control module. The control module monitors the current draw of the heater to determine if a failure is present.

If the ECM detects that the HO2S 1 heater current is below a specified value, this DTC sets.