METHOD AND DEVICE FOR DIAGNOSING TROUBLE WITH SENSOR FUNCTION

A sensor for converting a physical quantity into an electric signal and issuing the output is driven by a drive circuit which is driven by a drive signal issued from a 1-chip microcomputer. The 1-chip microcomputer judges fault of sensor function when the sensor output signal is out of a specified output range. Further, when stopping the operation of the drive circuit, if the sensor output signal does not coincide with a specific value, the 1-chip microcomputer also judges fault of sensor function. According to the invention, in the event of a trouble of sensor function allowing the sensor output signal to settle within an output range, such trouble can be detected.