Patent ID: 7701224

Claim:
A wire abnormality detecting device that detects an abnormality in a signal wire of a sensor switch that is inputted as a switch logic signal with respect to a microprocessor, wherein the microprocessor is disposed with at least a program memory including a program that serves as intermediate voltage state detecting means and detailed determining means including transitional period determining means and intermediate voltage abnormality determining means and an AD converter that measures the signal voltage level relating to the switch logic signals, the intermediate voltage state detecting means is means that determines, by monitoring the digital output of the AD converter, when the logic of the switch logic signal exceeds a first threshold corresponding to a first signal voltage when the logic of the switch logic signal is low and when the logic of the switch logic signals is less than a second threshold corresponding to a second signal voltage when the logic of the switch logic signal is high, the transitional period determining means is means that detects a transitional period when the logic level of the switch logic signal changes from a low to a high or from a high to a low level, the intermediate voltage abnormality determining means is means that acts when the intermediate voltage state detecting means has detected an intermediate voltage state, excluding a period when the transitional period determining means is detecting a transitional period, and determines that an intermediate voltage abnormality has occurred, and the wire abnormality detecting device detects, by the intermediate voltage abnormality determining means, an abnormality resulting from incomplete contact between the signal wire and a positive power source wire or a negative power source wire or from contact between the signal wire and another analog signal wire.