It is located inside the area where the pan covers. That’s all I know. I got various replies that all were guesses. Even the Toyota techs didn’t know which one it was.
There are a number of YouTube videos showing how to test the solenoids. This can be done without opening the transmission if you can get the AT electrical coupling apart. Testing with 12 VDC power to the solenoid wiring at the harness (or at the solenoid if you remove the tranny pan, OR at the wiring harness where it enters the ECM) will produce a “click” when the solenoid operates. If no click, then it’s that solenoid. Make sense?