Apparatus and Method for Diagnosing Failure of Bypass Valve

Some embodiments of the teachings herein include an apparatus for diagnosing bypass valve failure in an electric supercharger with a motor and an electric compressor comprising: a bypass valve on a bypass line branching from an intake line with the electric supercharger; and a control unit which assesses the vehicle-state information to determine whether failure criteria of a bypass valve start are satisfied. If the failure criteria are satisfied, the control unit transmits ‘open’ or ‘close’ control instructions to the bypass valve and transmits, to the electric supercharger, a specific rotational-speed target value for determining whether the bypass valve is in the normal open state or the normal closed state, thereby determining whether the bypass valve is subject to stuck-open failure or stuck-closed failure.