Shift Solenoid No 1, 2 (SS1, SS2)
WARNING: This page is about a different car, the 2004 Suzuki Swift + and 2004 Chevrolet Aveo. However, it is still accessible from the selected car via links, so may be relevant.
Two shift solenoids are installed directly in the valve body. The solenoids operate of ON and OFF by the control signal from TCM. Combinations of 2 solenoids, SS1 (2) and SS2 (1) changes gear ranges.
Courtesy of GENERAL MOTORS CORP.