| 摘要 |
An ECU (23) of an electric power steering system includes a driving circuit (32) configured as an H bridge circuit; a microcomputer (33) that controls the driving circuit (32); a capacitor (43) for stabilizing electric power that is supplied to the driving circuit (32); and a resistor (51) that is interposed in a second power supply path (L2) that bypasses a first power supply path (L1) in which the relay contact (41) is interposed. The microcomputer (33) causes a relay circuit (42) to be activated after the capacitor (43) is charged via the resistor (51) (second power supply path (L2)). The microcomputer (33) determines whether a stuck-open fault has occurred on the basis of a voltage difference between terminals of the relay contact (41) at the time when both FETs (35a and 35c) that are connected in series and that constitute the driving circuit (32) are turned on to cause the discharge of the capacitor (43) after the relay circuit (42) is activated.
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