ECM receive vehicle speed signal from ABS/ESP (HECU, Hydraulic Electrical Control Unit) module. HECU calculates vehicle speed with 4 wheel speed signals from each wheel. It sends vehicle speed signal to ECM, cluster, air conditioner control module, and BCM etc. through CAN communication. If more than one of wheel speed sensor in the rear is failed, it calculats the vehicle speed signals with 2 wheel speed sensor in the front.