Control method and control device for vehicular automatic transmission and recording medium

A control method for a control device for vehicular automatic transmission that comprises a torque converter comprising a lock-up clutch, wherein the control device comprises a first solenoid controlling the lock-up clutch to either an engaged state or a non-engaged state;

• and a second solenoid controlling an engagement pressure of the lock-up clutch between a released state and a fully engaged state;
• wherein the control method comprises:
• acquiring, when an accelerator pedal opening of a vehicle is on a deceleration side in a fully closed state, a slip ratio or a slip amount of the torque converter when the first solenoid is controlled to maintain in the engaged state for a predetermined time period and when the second solenoid is controlled such that the engaging pressure changes to a predetermined low pressure comprising the released state;
• and
• determining whether or not the second solenoid has a high-pressure fixation failure according to whether or not the slip ratio or the slip amount is within a predetermined range from a slip reference value.

A non-transitory recording medium, storing a program, functioning a computer as a control device for vehicular automatic transmission that comprises a torque converter comprising a lock-up clutch, wherein the control device comprises a first solenoid controlling the lock-up clutch to either an engaged state or a non-engaged state;

• and a second solenoid controlling an engagement pressure of the lock-up clutch between a released state and a fully engaged state;
• wherein the program comprises:
• a function of acquiring, when an accelerator pedal opening of a vehicle is on a deceleration side in a fully closed state, a slip ratio or a slip amount of the torque converter when the first solenoid is controlled to maintain in the engaged state for a predetermined time period and when the second solenoid is controlled such that the engaging pressure changes to a predetermined low pressure comprising the released state;
• and
• a function of determining whether or not the second solenoid has a high-pressure fixation failure according to whether or not the slip ratio or the slip amount is within a predetermined range from a slip reference value.