Seat-Occupancy Detection, Front Passenger

Seat-Occupancy Detection, Front Passenger

Seat-occupancy detection, front passenger
The front passenger seat occupancy detection detects whether the seat is occupied or not.
The design of the seat occupancy detection depends on the national version.
- Front passenger seat occupancy detection, Europe version:
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 front passenger side are also triggered even if the front passenger seat is unoccupied.

- Front passenger seat occupancy detector, 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. On detection, the airbags on the front passenger side are automatically disabled. The indicator light for front passenger airbag deactivation lights up.

Functional description
- Seat occupancy detection for front passenger, European version (will gradually be replaced with a revised version beginning from 09/2010 for all series):
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) via LIN bus. For example, if the passenger's seat is recognized as being occupied without the seat belt buckle switch sending a signal, a fasten belt warning will be emitted by the Crash Safety Module.
Persons can only be detected correctly if they assume the correct seating position, as both halves of the seat have to be loaded simultaneously.

The following graphic shows the seat-occupancy mat using example F01 up to 07/2012.







- Seat occupancy detection for front passenger, European version (revised version, will gradually be replaced beginning from 09/2010 for all series):
The seat-occupancy mat is installed on the underside of the foam insert.

The following graphic shows the seat-occupancy mat using example F01 from 07/2012.







- Front passenger seat occupancy detection, US version, via seat-occupancy mat with pressure sensors (up to 09/2009):
The seat-occupancy mat is installed on the underside of the foam insert. The crash safety module detects the seat occupancy status by evaluating the imprint on the seat cushion. This enables the crash safety module to decide whether to enable and disable the airbags on the front passenger side.
The distances of the surfaces and centres of gravity on the occupied seat cushion indicate whether an adolescent or adult with required size, or a small child, is in the child restraint system specifically designed for the purpose. The airbags on the front-front passenger side are deactivated automatically when a small child is detected. The indicator light for front passenger airbag deactivation lights up. If a person of adequate size sitting correctly is detected, the airbags on the front passenger 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 such cases, the seat position must be varied until the indicator light for front passenger airbag deactivation goes out (airbags activated).

The following graphic shows the seat-occupancy mat using example: F01.







- Front passenger seat occupancy detection, US version, via seat-occupancy mat with capacitive sensor system (from 09/2009):
The front passenger seat occupancy detection consists of a seat-occupancy mat with a capacitive sensor system. 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 front-front passenger 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 front passenger 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 such cases, the seat position must be varied until the indicator light for front passenger airbag deactivation goes out (airbags activated).
The evaluation electronics in the electronic component transmits the status information in cycles to the Crash Safety Module. The data is transmitted via the LIN bus.
If there is a breakage in the heating wire of the seat heating, the seat occupancy mat self-diagnosis makes a corresponding fault code entry in the Crash Safety Module.

The following graphic shows the seat-occupancy mat using example: F01.







Structure and inner electrical connection

The front passenger seat occupancy detection consists of:
- seat occupancy mat with pressure sensors
The seat occupancy mat consists of conductors and pressure sensors.
- Seat occupancy detection for front passenger, European version (will gradually be replaced with a revised version beginning from 09/2010 for all series):
The conductor paths are connected to the evaluation electronics in the electronic component.

- Seat occupancy detection for front passenger, revised European version, which will gradually be replaced beginning from 09/2010 for all series):
The conductor paths are connected in the Crash Safety Module (ACSM).

- Seat-occupancy mat with capacitive sensor system
The capacitive sensor system integrated in the seat-occupancy mat is connected to the evaluation electronics in the electronic component.

- Electronic component
In the electronic component, the sensor signals are processed, converted into digital signals and sent in cycles to the crash safety module. The data is transmitted via the LIN bus.
Possible fault statuses of the front passenger seat occupancy detection are saved in the fault memory of the Crash Safety Module.

The seat occupancy mat is supplied with voltage by the crash safety module (ACSM). (ACSM stands for "Advanced Crash Safety Module", referred to as the "crash safety module").
The following graphic shows the seat occupancy detection for front passenger, European version (will gradually be replaced with a revised version beginning from 09/2010 for all series):







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







The following graphic shows the seat occupancy detection for front passenger, revised European version, which will gradually be replaced beginning from 09/2010 for all series.







Diagnosis instructions

Failure of the component
If the front passenger seat occupancy detection fails, the following behavior is to be expected:
- Fault entry in the crash safety module
- Airbag indicator light is illuminated, only seat occupancy detection for front passenger, European version until 09/2010 (unrevised version) and US version
- Indicator lamp for front passenger airbag deactivation, only for US version.
- Airbags on the front passenger side are automatically deactivated, US version only, (front passenger airbag, side airbag, knee airbag)

Assume correct position for function check of front passenger seat occupancy detection

Assume correct position when performing a function check for the front passenger seat occupancy detection.
- Position buttocks as near as possible to the backrest (buttocks may touch the backrest).
- Legs slightly bent.
- Position the backrest as vertical as possible so that shoulder blades lie against the backrest.
- Do not support by placing hands on the seat surface.
- Sit in central position, not on the side sections of the seat.
- Seat height adjustment in central position.

The following graphic shows the correct seating position on the front passenger seat for function check of front passenger seat occupancy detection.







General notes

Replacing the seat occupancy mat, front passenger (US version)

Following replacement of the seat-occupancy mat with capacitive sensor system, the seat-occupancy mat must be enabled. A service function is available for initialization.
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.