Headlight Solenoid Circuit: Description
WARNING: This page is about a different car, the 2008 Lexus IS F. However, it is still accessible from the selected car via links, so may be relevant.
This Bi-function is activated by the front controller. The front controller receives a HI beam turn ON signal from the main body ECU RH and activates the headlight solenoid built into the headlight unit to slide the shade down.
When the LO beam headlight is switched on, the upper illumination area of the discharge bulb is blocked by the shade and only the lower illumination area is used. When the HI beam is turned on, the headlight solenoid slides the shade down to allow use of the upper illumination area, thus increasing the illumination area and improving visibility when the HI beam is on.