The speed sensor is able to detect the velocity of the wheels and send corresponding data to the ECU. This information is used to control the ABS. Each sensor has front and rear rotors of 48 splines each. As the rotors begin to rotate, the magnetic force field produced by a magnet in the sensor produces an alternating voltage. As the rate of this AC voltage changes with rotor speed, the ECU uses the pulse rate to determine the velocity of each wheel.
When the DTC code C0205 OBDII is stored, it means that a problem was detected with the signal provided by the Left Front Wheel Speed Sensor.