Patent attributes
In system and method of controlling an automatic transmission that includes a lowest gear-stage friction element and has a lowest gear stage having a largest gear ratio and a gear stage other than the lowest gear stage, the lowest gear stage being established through engagement of the lowest gear-stage friction element, the gear stage other than the lowest gear stage being established while the lowest gear-stage friction element is kept in disengagement, a temperature of working oil in the automatic transmission is sensed, and use of the lowest gear stage is inhibited and use of the gear stage other than the lowest gear stage is allowed when the sensed temperature of the working oil is lower than a first predetermined temperature as a predetermined extremely low temperature at which an engagement failure of the lowest gear-stage friction element is caused.
