Shift switching device and shift switching method

摘要

A shift-by-wire shift switching device and shift switching method that switch a shift range of an automatic transmission using an electric motor. The shift switching device includes a controller that determines whether a fault has occurred in a current supply line of each phase of the electric motor on a phase-by-phase basis, executes an open-loop control of the electric motor using only the phases in which it has been determined that a fault has not occurred, and determines whether a fault has occurred in the current supply line by detecting an activation state of the electric motor when the open-loop control of the electric motor is executed. Therefore, it is possible to determine whether a fault in the motor is a short-circuit fault or a break fault, without addition of a part such as a short-circuit detection sensor.