ECU Power Source Circuit [12/2023 - ]: Description
WARNING: This page is about a different car, the 2024 Lexus TX 550h+. However, it is still accessible from the selected car via links, so may be relevant.
If the ignition switch is ON, the hybrid vehicle control ECU assembly applies current to the MREL terminal to turn the IGCT SCENE relay on. This supplies power to the IGCT terminals.