Several control units are applied to electronically controlled vehicles. These units perform each control with informations from various sensors. Thus, sharing signal information from sensors is needed, so CAN communication type whose communication speed is high and insensitive to electrical noise by spark generation is adopted to controlling unit(ECM/PCM, ABS, EPS, FATC, CLUSTER, etc). CAN communication consists of CAN BUS HIGH, CAN BUS LOW and two 120Ω resistances in circuit. In order to operate it's SPAS function, the MDPS unit gets the status of gear-shifting from TCU in a vehicle with A/T.

The EPS ECU sets DTC C1696 if it doesn't receive SPAS signals from SPAS module through CAN communication.