Pattern Select Switch EV Mode Circuit [08/2013 - ]: Description
WARNING: This page is about a different car, the 2014 Lexus ES 300h. However, it is still accessible from the selected car via links, so may be relevant.
The EV drive mode signal will be sent to the power management control ECU when the EV drive mode switch is operated. If the specified conditions are met, the system enters EV drive mode and the vehicle will be driven using EV drive mode. This signal is then transmitted from the power management control ECU via CAN to the combination meter assembly to illuminate the EV drive mode indicator light.