A communication system for an automotive, comprising a plurality of electrical controller units (1, 1a, 1b), a first electrical controller unit of which has an active mode and a low consumption mode; and a communication bus (CAN Bus) coupled with the electrical controller units (1, 1a, 1b) for transmitting a message between the electrical controller units (1, 1a, 1b), when the first electrical controller unit is in the low consumption mode, wherein a second electrical controller unit outputs a first message (20, S304) to the communication bus (CAN bus) after the second electrical controller unit outputs a second message to the communication bus (CAN bus), when the first electrical controller unit receives the first message (20, S304) via the communication bus (CAN bus), checks an ID in the first message (20, S304) whether the ID designates the first electrical controller unit or not, and shifts to the active mode from the low consumption mode when the ID designates the first electrical controller unit, and characterized in that: when a third electrical controller unit receives the second message via the communication bus (CAN bus), the third electrical controller unit stops outputting the message to the communication bus (CAN bus) during a predetermined period during which the second electrical controller unit outputs the first message (20, S304) to the communication bus (CAN bus), and the first message (20, S304) is output according to a first communication protocol and the second message is output according to a second communication protocol, the second communication protocol being different from the first communication protocol. a plurality of electrical controller units (1, 1a, 1b), a first electrical controller unit of which has an active mode and a low consumption mode; and a communication bus (CAN Bus) coupled with the electrical controller units (1, 1a, 1b) for transmitting a message between the electrical controller units (1, 1a, 1b), when the first electrical controller unit is in the low consumption mode, wherein a second electrical controller unit outputs a first message (20, S304) to the communication bus (CAN bus) after the second electrical controller unit outputs a second message to the communication bus (CAN bus), when the first electrical controller unit receives the first message (20, S304) via the communication bus (CAN bus), checks an ID in the first message (20, S304) whether the ID designates the first electrical controller unit or not, and shifts to the active mode from the low consumption mode when the ID designates the first electrical controller unit, and characterized in that: when a third electrical controller unit receives the second message via the communication bus (CAN bus), the third electrical controller unit stops outputting the message to the communication bus (CAN bus) during a predetermined period during which the second electrical controller unit outputs the first message (20, S304) to the communication bus (CAN bus), and the first message (20, S304) is output according to a first communication protocol and the second message is output according to a second communication protocol, the second communication protocol being different from the first communication protocol. when a third electrical controller unit receives the second message via the communication bus (CAN bus), the third electrical controller unit stops outputting the message to the communication bus (CAN bus) during a predetermined period during which the second electrical controller unit outputs the first message (20, S304) to the communication bus (CAN bus), and the first message (20, S304) is output according to a first communication protocol and the second message is output according to a second communication protocol, the second communication protocol being different from the first communication protocol.