| 摘要 |
PURPOSE:To sufficiently diagnose a signal processing circuit and an ignition switch element by sending current as much as ignition current to a dummy load resistor while drive means is being bypassed, and thereby diagnosing faults with the voltage level of a first acting switching means detected. CONSTITUTION:It microcomputer 5a allows the base of a transistor 10 to be energized via a buffer 5b at the time of diagnosis, so that the transistor is turned on, and a multiplexer 11 is switched to the side of a D/A, converter 5f via a buffer 5d. In the second place, a signal equivalent to that for collision is outputted to the D/A converter 5f, so that a dummy signal is outputted so as to be supplied to a signal processing circuit 7. In this case, a transistor 4 is turned on, provided that the signal processing circuit 7, a buffer 8 and the ignition transistor 4 are normal. This constitution thereby allows current as much as ignition current to flow in the path. Voltage at the point A is then inputted via a D/A converter 5e so as to be compared with specifications, and when the voltage is out of the specifications, an alarm lamp 12 is lit via a buffer 5c. |
