Patent ID: 8175767

Claim:
A diagnostic apparatus in which a drive circuit is configured of switching means for supplying an electric current to a linear solenoid valve and variably regulating a valve opening degree on the basis of inputted ON-OFF signals, current detection means for detecting an electric current flowing from the switching means to the linear solenoid valve, and control means for calculating a target current that has to be supplied to the linear solenoid valve on the basis of a target opening degree, outputting an OFF signal to the switching means when the detected current value exceeds the target current value and outputting an ON signal to the switching means when the detected current value is equal to or less than the target current value so that the linear solenoid valve maintains the target opening degree, and which diagnoses a ground short of the drive circuit and the linear solenoid valve, the diagnostic apparatus comprising: ground short detection means for detecting a switching of ON-OFF signals to be inputted in the switching means and determining a ground short fault when the number of ON-OFF switching cycles per a predetermined interval is equal to or less than a predetermined fixed number of cycles.