Seat Occupancy Sensor is an electronic sensor installed in a vehicle seat (usually the front passenger seat) that detects whether someone is sitting in the seat. It is an important part of a vehicle's airbag and seat belt reminder systems.
How it works
The sensor uses one or more technologies to determine seat occupancy, such as:
Pressure sensors that detect weight on the seat
Capacitive sensors that detect the presence of a person
Strain gauges or load sensors that measure force on the seat frame.
Main functions
Passenger detection: Determines whether the seat is occupied.
Airbag control(for car): Enables or disables the passenger airbag depending on occupancy and, in some vehicles, the occupant's weight.
Seat belt reminder: Activates seat belt warning lights or alarms if an occupant is detected but the seat belt is not fastened.
Child safety: Helps prevent airbag deployment when a child seat or a very light occupant is detected (depending on the vehicle's design).
Common applications
Passenger cars
SUVs
Trucks
Buses
Commercial vehicles
Symptoms of a faulty Seat Occupancy Sensor
Airbag warning light stays on.
Passenger airbag remains disabled when an adult is seated.
Passenger airbag indicator behaves incorrectly.
Seat belt warning sounds even when the seat is empty, or fails to sound when occupied.
A diagnostic trouble code (DTC) is stored in the vehicle's control module.