| 摘要 |
<p>PURPOSE:To prevent the malfunction of function which copes with abnormality to be generated based on erroneous diagnosis by not diagnosing a sensor circuit system and an actuator circuit system when a supply voltage is lower. CONSTITUTION:When the trouble diagnostic processing is started, old data is cleared, and initial values are set to prescribed registers. Before practical trouble diagnosis, an output A of a supply voltage discriminating circuit 40 inputted to a port P5 is checked to judge whether the supply voltage is normal or not. A voltage reduction detection signal is generated in the output A if the supply voltage is lower than the reference value which secures the normal operation of the sensor circuit system and the actuator circuit system, and the voltage reduction detection signal is generated in an output B if the supply voltage is lower than the second reference value lower than said reference value. The voltage reduction detection signal from the output B of the supply voltage discriminating circuit 40 acts upon a reset circuit 24 to reset a microcomputer 20, thus stopping the program executing operation.</p> |
