DTC P0973: Shift Solenoid "A" Control Circuit Low (Shift Solenoid Valve S1); DTC P0974: Shift Solenoid "A" Control Circuit High (Shift Solenoid Valve S1) [04/2013 - 08/2015]: Wiring Diagram
WARNING: This page is about a different car, the 2015 Lexus IS 250 and 2014 Lexus IS 250. However, it is still accessible from the selected car via links, so may be relevant.