When you move the selector lever into SST does the electronic indicator on the instrument cluster display the selected gear? If not the problem could be with the transmission control switch, inside the transmission shift selector, or the wiring itself. The transmission control switch gets voltage from fuse 6 in the central junction box, but so does the antilock brake system. I would think if fuse 6 was open you would also have problems with the antilock brake system.
If you have a scan tool that can read data you could look at the data for the transmission control switch, the manual mode + switch and the manual mode - switch to verify their operation.