Technical information

Knee airbag on driver's and passenger's sides.
In the event of a crash, when the driver or front passenger is not wearing a seat belt, the knee airbag will support their
knees.
This results in the upper body being shifted forwards in a controlled manner and being caught by the airbag.
The knee airbag on the driver's side is located underneath the steering column behind a lid.
The knee airbag on the passenger's side is located in the lid of the glove box behind a cover.
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Ignition sequence
The airbag is deployed by the airbag control unit and/or the responsible satellite (= intelligent sensor).
The integrated sensors activate the required systems when the triggering thresholds are exceeded. In the gas generator,
the solid propellant sodium azide or nitro-cellulose mainly burns to nitrogen gas. Negligible volumes of carbon monoxide
and nitrogen oxide are produced. This gas then flows into the airbag and unfolds it. As the airbag unfolds, the cover
(impact absorber of driver's airbag, cover of the front passenger airbag, trim panel of the side/head airbags) tears off at
the predetermined breaking points.
The deposits of talc from the airbag in the vehicle interior are totally safe.
Safety mechanisms
The restraint and safety systems are triggered by electronic and mechanical acceleration sensors. Two sensors that
function independently of one another are always needed for airbag deployment.
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Electronic acceleration sensors
Driver's and front passenger airbag, head and side airbags, belt tensioner and safety battery terminal.
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Mechanical acceleration sensors (safing sensor)
The driver's and front passenger airbags are triggered in conjunction with the mechanical acceleration sensors.
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Electronic side impact sensors
The side and head airbags are triggered in conjunction with the electronic acceleration sensors.
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Airbag control unit
The airbag control unit is the central unit in the entire restraint and safety system and carries out the following tasks:
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Impact detection
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Calculation of triggering time for airbags, belt tensioner, safety battery terminal
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Ignition of airbags, belt tensioner and safety battery terminal
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Self-test
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Fault display and fault memory with diagnostic capability
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Seat occupancy and weight recognition for the front passenger seat
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Satellites
Satellites consist of a control unit with an integrated sensor system for activating actuators (airbags, belt tensioner, etc.).
Satellites are able to make intelligent decisions on selective and fast triggering of actuators. Any functions not needed are
not activated.
In the 7 Series (E65/66) models, the Intelligent Safety Integration System (ISIS) and, from the 5 Series (E60/E61), 6
Series (E63/E64) and Z4 (E85) models, the passive safety system (ASE) are installed with satellites.
Belt tensioner - technical information
Four different belt tensioner systems are used in the vehicles:
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Mechanical belt tensioners
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Pyrotechnic belt tensioners
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Pyrotechnic retractor tensioners / end fitting pretensioners
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