Front passenger seat occupancy detection via seat-occupancy mat with capacitive sensor system (US version)
According to the regulations of the NHTSA (National Highway Traffic Safety Administration), a small child in the child restraint system specifically designed for the purpose on the front passenger seat must be detected automatically. If the front passenger seat is detected as "occupied" with a child restraint system specifically designed for the purpose, the MRS control unit automatically disables the airbags on the front passenger side (front passenger airbag, side airbag, knee airbag). The indicator light for front passenger airbag deactivation lights up.
| Item | Explanation |
|---|---|
| 1 | Evaluation electronics |
| 2 | Seat-occupancy mat with capacitive sensor system |
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 resistance of the human body.
Classification of the occupancy status is based on the evaluation of the capacitive resistance. The electronic evaluation unit picks up the change and determines the corresponding status.
The airbags on the passenger's side are deactivated automatically when 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).
This behavior occurs primarily with devices that are connected to the vehicle electrical system via a USB cable or other charger adapter.
In vehicles with an acoustic seat belt warning, this could cause the warning signal to sound.
Moisture on the seat surface can also cause a faulty seat occupancy detection.
The electronic evaluation unit sends the status information in cycles to the MRS control unit. Possible fault states are stored in the fault memory of the MRS control unit.
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.
If there is a breakage in the heating wire of the seat heating, the seat-occupancy mat self-diagnosis makes a corresponding fault entry in the MRS control unit.