System and method for determining when a selectable one-way clutch has mechanically released

A method for determining when a selectable one-way clutch (SOWC) of a transmission has mechanically released, the transmission having a multiple gearsets, at least one internal speed sensor and at least one output speed sensor, the method comprising:

• in a first algorithm measuring each of a converter model engine torque, a transmission input torque, and a torque converter slip;
• in a second algorithm calculating an SOWC slip;
• and
• issuing a SOWC released signal if either all of the measured converter model engine torque, the measured transmission input torque, and the measured torque converter slip are positive, or the calculated SOWC slip is greater than a predetermined threshold.

A system for determining when a selectable one-way clutch (SOWC) of an automatic transmission has mechanically released, comprising:

• an update timer for identifying if each of a converter model engine torque, a transmission input torque, and a torque converter slip are positive for a predetermined period of time;
• a SOWC slip value calculated using an output signal from each of:
• at least one transmission internal speed sensor producing an output signal representative of a speed of an internal component of a transmission;
• and
• at least one transmission output speed sensor producing an output signal representative of a speed of an output of the transmission;
• and
• a SOWC released signal issued if either all of the measured converter model engine torque, the measured transmission input torque, and the measured torque converter slip are positive for at least the predetermined period of time, or the calculated SOWC slip value is greater than a predetermined threshold.