Dimmer Signal Circuit: Description
WARNING: This page is about a different car, the 2006 Lexus RX 400h. However, it is still accessible from the selected car via links, so may be relevant.
The multiplex network body ECU sends a panel illumination signal to the radio receiver through this circuit.
The multiplex network body ECU determines the ambient brightness based on the light level detected by the automatic light control sensor and performs dim control.