| 摘要 |
Five ECUs (1 to 5) control vehicle devices using CAN protocol. Each of ECUs (1 to 5) is provided with a resistor (41) and a switch (43) for activating the resistor (41). A first and fifth ECUs (1, 5) are arranged on the leftmost and rightmost ends. Resistors (41) of the first and fifth ECUs (1, 5) are used as terminating resistors to a two-wire communications line (13). When the two-wire communications line (13) is broken, the first ECU (1) sends a test signal while other ECUs (2, 3, 4) excluding the fifth ECU (5) turn on the switches (43) from right to left. When the test signal can be received, a broken point is located on the right side of ECU (2, 3, 4) that turns on its switch (43) at that time. Thereafter ECUs (1 to 4) on the left side of the broken point conduct communication. <IMAGE>
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