Circuit Description
WARNING: This page is about a different car, the 2004 Toyota Corolla. However, it is still accessible from the selected car via links, so may be relevant.
The shift solenoid valve SL is turned "ON" and "OFF" by signals from the ECM in order to control the hydraulic pressure operation, the lock-up relay valve, which then the controls operation of the lock-up clutch.
Fail safe function:
If the ECM detects a malfunction, it turns the shift solenoid valve SL OFF.