Impreza Wagon FWD F4-1820cc 1.8L SOHC (1995)
Heated Oxygen Sensor: Description and Operation
Oxygen Sensor Heater
PURPOSE/OPERATION
The O2 sensor does not operate until a certain temperature is reached. The heater warms the sensor up faster than if it had to rely simply on
exhaust gas heat. The MPFI system then controls the A/F mixture sooner, reducing exhaust emissions.