CONTROL SYSTEM OF AIR-FUEL RATIO SENSOR

A control device selectively executes first and second energization control for controlling an energization amount to the heater. The first energization control is executed to keep temperature of a sensor element within an active temperature region. The first energization control is PWM control in which the energization amount is controlled with closed loop control such that an impedance of the sensor element matches a target value. The second energization control is PWM control in which the energization amount is controlled with open loop control so as to keep the temperature of the sensor element within a preset temperature region that is lower than the active temperature region. The control device executes the second energization control during an internal combustion engine is stopped while executing the first energization control during the internal combustion engine is not stopped.