You guys are incorrect all around in regards to the airbag sensors, at least for US cars! See
this thread I started a while back. The front and side impact airbags are indeed tied to the front passenger seat occupancy sensor. Read below:
European and US passenger airbag functionality is vastly different.
For F22 M240i:
Front passenger seat occupancy detection (Europe version):
The front passenger seat occupancy detection comprises a seat occupancy mat with conductor paths and
pressure sensors. The resistance value of the pressure sensors is read in and evaluated in the Crash Safety Module (ACSM) (ACSM stands for "Advanced Crash Safety Module", hereinafter "Crash Safety Module").
The seat-occupancy detector is
only used for the seat belt warning. If the seat occupancy mat detection indicates that the front passenger seat is occupied, the passenger belt must also be inserted in the belt buckle. The seat belt warning then goes out. If the crash safety module triggers the airbags, the corresponding
airbags on the passenger's side are also triggered even if the front passenger seat is unoccupied.
Functional description
When a weight is placed on the seat, resistance in the seat occupancy mat changes. The
seat is detected as not occupied up to a weight of approximately 12 kg (only applies if the seat-occupancy mat is installed between the cover and the foam insert of the seat). The seat occupancy detection function, however, also depends on the type of seat. e.g.: The material tension in a leather seat or a taut sports seat is already interpreted as pressure on the sensors. In such cases, a weight below 12 kg can trigger the "seat occupied" condition.
The resistance value is transmitted to the Crash Safety Module (ACSM) in a direct wire. For example, if the passenger's seat is recognised as being occupied without the seat belt buckle switch sending a signal, a fasten belt warning will be emitted by the Crash Safety Module.
************************************************** ************************************************** *************
Seat occupancy detector, front passenger (US version):
In accordance with the stipulations of the National Highway Traffic Safety Administration (NHTSA) a small child in a child restraint system on the front passenger seat must be automatically detected.
Upon detection, the airbags on the passenger's side are automatically deactivated (front passenger airbag, side airbag, knee airbag). The indicator light for front passenger airbag deactivation lights up.
Functional description
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).
Notice!
Electronic devices that are placed on the front passenger seat, e.g. laptop computers, mobile phones etc., could cause the front passenger airbag to activate.
This behaviour 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 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.
Failure of the component:
If the front passenger seat occupancy mat fails, the following behaviour is to be expected:
Fault entry in the crash safety module (ACSM)
Airbag warning lamp lights up
Indicator lamp for front passenger airbag deactivation (only for US version)
Airbags on the passenger's side are automatically deactivated (front passenger airbag, side airbag, knee airbag)