AN IN-VEHICLE SYSTEM FOR SUPPRESSING THE STANDBY POWER OF ELECTRONIC CONTROL UNITS

An in-vehicle network system includes a power supply (10), an upper electronic control unit (ECU) (11), an intermediate ECU (21, 22) configured to communicate with the upper ECU, and a plurality of lower ECUs (31, 32) configured to communicate with the intermediate ECU. The intermediate ECU is configured to receive power supplied from the power supply, and maintain the lower ECUs in a power-off state until the intermediate ECU receives a message from the upper ECU and supply the power supplied from the power supply to the lower ECUs in response to the message transmitted from the upper ECU. The lower ECUs are configured to transition, when the power is supplied from the power supply, from the power-off state to a standby state to wait for an instruction.