The Oxygen Sensors (HO2S) are pieces used by the motor control module PCM (Power Train Control Module); to determine the oxygen content that is in the exhaust system.
The information obtained from bank 1, Oxygen Sensor 3 (HO2S) is used by the PCM to monitor the performance of the catalyst; an integral part of this sensor is a heater, which is controlled by the PCM to heat the temperature sensor operation, and in this way the motor can enter into a closed loop faster, as well as reduce emissions when starting when it is cold.
The heater circuits are monitored regularly by the PCM, in case there is an abnormal voltage. It is important to know how the heater of your vehicle is controlled because the PCM activates the heater in several circumstances.