Occupant Weight Sensor (OWS)

Fig 1: Identifying Occupant Weight Sensor (OWS)

Courtesy of VOLVO CARS CORPORATION

The occupant weight sensor (OWS) consists of three interactive components: 

• The pressure sensor, installed under the front passenger seat
• The seatbelt force sensor, mounted in the seat frame on the outside of the front passenger seat
• Occupant weight sensor module, installed under the front passenger seat.

The pressure sensor registers the pressure the seat is exposed to, for example when someone is sitting in the car. Information from the seat belt force sensor is also used to ensure the good performance of the system. The seatbelt force sensor informs the occupant weight sensor module what force the belt is tensioned with. This is done because the pressure measured by the pressure sensor can be affected by the passenger fastening the seatbelt over themselves or child seat tightly. This means that the passenger or child seat exerts greater pressure on the seat than during normal seatbelt use. The passenger or child seat is then interpreted as being heavier than he or she is. The occupant weight sensor module uses the information from both the pressure sensor and seatbelt force sensor to calculate the actual weight of the passenger. The occupant weight sensor (OWS) transmits continuous signals on the local controller area network (CAN) which the supplemental restraint system module (SRS) and occupant weight sensor (OWS) are connected to. If the occupant weight sensor (OWS) does not function correctly the supplemental restraint system module (SRS) will:

• deactivate the front passenger airbag
• light the warning lamp for passenger airbag disconnected (PAD) in the roof console
• light the SRS (supplemental restraint system) indicator lamp and display the alert message in the driver information module (DIM).

If a fault occurs in any of the components the following should be noted:

• The pressure sensor and occupant weight sensor module must be replaced at the same time
• The seatbelt force sensor is replaced separately.