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. The EPS unit lets a warning lamp turn on by CAN communication.

If the MDPS ECM/PCM gets invalid signals from cluster, it sets C1656.