A hydraulic control apparatus of a vehicular automatic transmission has a
plurality of hydraulic friction engagement devices that are selectively
engaged and released to establish a plurality of forward speed change
stages of different speed change ratios. The forward speed change stages
are achieved through engagement of predetermined friction engagement
devices, of the plurality of friction engagement devices. If it is
determined that a predetermined speed change stage corresponding to a
predetermined shift output is not established, the hydraulic control
apparatus identifies a hydraulic friction engagement device having a bad
engagement that is a cause of the non-establishment of the predetermined
speed change stage, on the basis of the state of engagement oil pressure
of the predetermined friction engagement device.