Patent ID: 6966862

Claim:
A shift control system of an automatic transmission, a hydraulic pressure circuit having a constitution provided with solenoid hydraulic pressure control valves for controlling individually an engagement pressure and a disengagement pressure to a plurality of friction elements related to a shift of the automatic transmission, the shift control system of the automatic transmission including a shift controlling means for achieving a plurality of forward gears by outputting the following commands when the shift is requested; an engagement pressure control command to the solenoid hydraulic pressure control valves of the friction elements which is disengaged at a gear before the shift and is engaged at a gear after the shift, and a disengagement pressure control command to the solenoid hydraulic pressure control valves of the friction elements which is engaged at the gear before the shift and is disengaged at the gear after the shift, the shift control system of the automatic transmission comprising: 1) a hydraulic pressure sensing means for sensing whether or not a pressure of the friction elements is present, the hydraulic pressure sensing means being disposed on the plurality of the friction elements or each of engagement-disengagement hydraulic pressure passages; 2) an electric failure determining means for determining that an electric system is in failure through: a comparison between the following friction elements, when a hydraulic pressure sensing signal is inputted from the hydraulic pressure sensing means and when any of the forward gears is held: a supposedly-engaged friction element of the friction elements which is supposed to be engaged at the any of the forward gears, and an actually-engaged friction element of the friction elements which is sensed by the hydraulic pressure sensing signal to be actually engaged, and a determination that the supposedly-engaged friction element is not in accordance with the actually-engaged friction element; and 3) an electric failure interlock escaping means for sticking the gear of the automatic transmission to a given gear when the electric failure determining means determines that the electric failure is caused.