To determine whether a three-axle type power input/output device such as planetary gear can sufficiently exhibit its function.
An abnormality of locking generation in a power distribution integration mechanism is determined (S110-S150) when switching a load operation and a no load operation of an engine is executed at a frequency of a threshold Fref or larger in a state that the power distribution integration mechanism is rotation-synchronized. This determination is based on a following phenomenon. That is, the engine cannot be operated at a target rotation speed when the lock is generated in the power distribution integration mechanism during travel, a battery is thereby charged or discharged over a range of a charge accumulation state of a target, and the engine is switched repeatedly between the load operation and the no load operation, as a result thereof, to generate the phenomenon.
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