Occupant Detection Sensor & Seat Belt Buckle Switch
WARNING: This page is about a different car, the 2002 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
The ON/OFF signals of the occupant detection sensor that is built into the front passenger seat and the seat belt buckle switch determine whether the front passenger seat is occupied. The signals are then transmitted to the headlight beam level control ECU. The occupant detection sensor is shared with the seat belt warning system.