Patent ID: 6938190

Claim:
A failure detector for a communication network in an automobile, the communication network including a main ECU communicating with a plurality of sub-ECUs through a communication line, the failure detector being included in the main ECU, the failure detector comprising: means for receiving messages, which are composed of data to be used for controlling functions of the automobile, periodically transmitted from the plurality sub-ECUs with a respectively different message-sending interval predetermined for each sub-ECU; means for counting number of receipts of the messages from each sub-ECU; means for periodically monitoring the number of receipts counted in a monitoring interval which is longer than the message-sending interval; means for comparing the number of receipts counted in a monitoring interval with a criterion number predetermined respectively for each sub-ECU; and means for determining that one of the sub-ECUs is under failure if the number of receipts of the messages from that sub-ECU is smaller than the criterion number predetermined for that sub-ECU.