Patent attributes
An automatic transmission includes a planetary gear arrangement, and a plurality of engaging elements each arranged to vary an engagement state among the rotating elements of the planetary gear arrangement in such a manner to establish a normal gear ratio set and an emergency gear ratio set excluded from the normal gear ratio set. A control section performs the following: selecting a gear from the normal gear ratio set in accordance with a running state of a vehicle under normal operating conditions; controlling the engagement state of each of the engaging elements in such a manner to shift into the selected gear; establishing, when an interlock state is detected, an escape gear by releasing one of the engaging elements needed to be applied to establish the selected gear; and identifying an incorrectly-applied engaging element in accordance with the running state of the vehicle resulting from establishing the escape gear.
