The controller is built into the flat blade type wiper motor, and it communicates the control information and diagnosis information with the BCM via the LIN communication circuit. The BCM sends information such as wiper speed requests, rain and light sensor status, outside air temperature, and vehicle speed to the wiper motor. The wiper motor operates the wiper according to the information received from the BCM. The wiper motor has a self-diagnosis function, and sends an error signal to the BCM via the LIN communication circuit if it detects any abnormal conditions. If the BCM receives an error signal from the wiper motor, the DTC is set.