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.

If the EPS (MDPS=Motor Driving Power Steering) ECM/PCM doesn't get some signals from TCU, it sets C1612.