Functional description: Notes

The front passenger seat occupancy detection consists of a seat occupancy mat with a capacitive sensor system and evaluation electronics. The occupancy of the front passenger seat is detected by measuring the capacitive resistance of the human body.

The electronic evaluation unit picks up the change and determines the corresponding status.

The airbags on the passenger's side (front passenger airbag, side airbag, knee airbag) are deactivated automatically when the seat is empty or a small child is detected in the child restraint system provided for this purpose. The indicator light for front passenger airbag deactivation lights up.

If a person of adequate size sitting correctly is detected, the airbags on the passenger's side are activated. The indicator light for the front passenger airbag deactivation does not light up.

The front passenger airbag could deactivate with a youth or adult seated in certain positions (indicator light for passenger airbag deactivation comes on). In these cases, the seat position must be changed until the indicator light for the front passenger airbag deactivation goes out (airbags on the passenger's side are activated).

The evaluation electronics transmit status information to the Crash Safety Module (ACSM) in cyclical transmissions. Potential fault statuses are stored in the Crash Safety Module's (ACSM) fault memory. If the seat occupancy mat is defective, the airbags on the passenger's side are automatically disabled (front passenger airbag, knee airbag, side airbag). The indicator light for front passenger airbag deactivation lights up.

The following graphic shows the seat occupancy mat with capacitive sensor system using the example F25.

Fig 1: Identifying Seat Occupancy Mat With Capacitative Sensor Components

Courtesy of BMW OF NORTH AMERICA, INC.