HID Control Unit
WARNING: This page is about a different car, the 2011 Nissan Murano. However, it is still accessible from the selected car via links, so may be relevant.
Headlamp (LO) circuit is connected to HID control unit integrated in the headlamp. Headlamp (LO) circuit turns xenon headlamp ON.
For the details of HID control unit and the xenon headlamp, refer to "XENON HEADLAMP ".