System Outline
WARNING: This page is about a different car, the 2008 Lexus LX 570. However, it is still accessible from the selected car via links, so may be relevant.
Shift Lock Mechanism
If the brake pedal is depressed and the engine switch is pushed to the on (IG) position, the shift lock control ECU sub-assembly will be activated, which will allow the driver to change the shift lever to a position other than the P position.