System Functions

65 05 05 (138)
Crash safety (ACSM)
E60, E61, E63, E64, E70, E85, E93





System functions
The following safety system functions are described:

- Self-test
- Impact detection
- Triggering of safety system
- Data storage in the case of safety system triggering
- Message to other control units
- Visual and audible seat belt warning
- Emergency call
- Monitoring of battery cable



Self-test
In addition to all the inputs and outputs, the crash safety module also monitors the internal components (self-test). Possible fault codes are stored in the crash safety module. In the event of a system fault or a component fault, the airbag warning lamp lights up.
The crash safety module performs a self test after the ignition is switched on. During this time, the airbag indicator lamp will light up (approximately 3 to 5 seconds). The airbag indicator lamp goes out when the safety system is operational.
- The airbag indicator lamp come on if the crash safety module receives no CAN message from the instrument cluster.
- The airbag warning lamp remains on if the crash safety module detects an existing fault or one that has been stored during the self-test or while the vehicle is in motion.
- If the safety system detects a fault, operability of the safety system is partially maintained, subject to the following preconditions:
- If a fault is detected in a power circuit of the safety system, only the affected circuit is deactivated. The other airbags and belt tensioners remain operational.
- If there is a fault in the airbag warning lamp circuit, the lamp does not light up during the self-test. If there is no other fault, the safety system remains fully operational.
- The entire safety system is deactivated if there is an internal fault in the crash safety module or in the power supply. (The airbag and seat belt indicator lamps light up, check control symbol in the LCD)



Impact detection
The crash safety module can detect an impact from any angle (360°).
The direction and severity of an impact is detected by the acceleration sensors in the crash safety module and by external acceleration sensors.
External acceleration sensors:
- Front airbag sensor, driver's side and front airbag sensor, passenger's side
- Airbag sensor on driver's door and airbag sensor on front passenger's door
- Airbag sensor on driver's side B-pillar and passenger's side B-pillar
The crash safety module processes all acceleration data. This is used to determine the accident severity.



Triggering of safety system
Extensive testing has allowed the triggering thresholds to be determined for all possible types of accidents.
The following triggering thresholds were set for activating the different restraint systems:
- Seat belt tensioners
- End fitting pretensioner
- Front airbags
- Knee airbags
- Side airbags
- Head airbags
- Active head restraint
- Adaptive belt force limiter
The restraint systems are triggered only when 2 independent sensors detect the corresponding threshold.
For example, a frontal collision is detected by the longitudinal acceleration sensor in the airbag sensor in the driver's side B-pillar and by the longitudinal acceleration sensor in the crash safety module. The crash safety module calculates the direction of the impact and the collision severity from the data sent by the sensors. Depending on accident severity, the safety battery terminal is activated and the electric fuel pump switched off.



Triggering of the various restraint systems is illustrated based on two examples (frontal impact and side impact):
- Head-on collision
The restraint systems (seat belt tensioner, end fitting pretensioner, front airbag, knee airbag, adaptive belt force limiter) are triggered when the force of the frontal impact is so strong that the triggering thresholds in the crash sensor module are exceeded.
The belt tensioners have a lower triggering threshold than the front airbags. This means that depending on accident severity, only the belt tensioner may be activated by the crash safety module.
If the seat belt buckle switch is faulty, the crash safety module will attempt to activate the belt tensioner in spite of the error message.
If the seat-occupancy detector is faulty, the control unit assumes that the passenger seat is occupied. The restraint systems are activated.
Depending on accident severity, the safety battery terminal is activated and the electric fuel pump switched off.
- Side impact
If the triggering threshold in the crash safety module is exceeded, the side airbag and the head-level airbag on the side affected by the impact are activated.
Depending on accident severity, the safety battery terminal is activated and the electric fuel pump switched off.



Data storage in the case of safety system triggering
When the restraint systems trigger, certain data are written to a read only memory in the crash safety module. The data are used for accident research purposes (no access for service purposes).



Message to other control units
The crash safety module sends a message to other control units when the restraint systems are triggered. The following functions are performed by the relevant control units depending on the severity of the accident:
- Switching off the electric fuel pump:
- via the EKP control unit
(on vehicles with electronic fuel pump control)
- via the DME control unit
(on vehicles with no electronic fuel pump control)

- Switching off the alternator (via DME control unit)
- Opening central locking:
> E60, E61, E63, E64
- at the front via the body-gateway module (KGM)
- at the rear via the basic body module (KBM)
> E85
via the general module (GM)
> E70, E93
via the junction box electronics (JBE)
- Switching on interior lights
> E60, E61, E63, E64
via the body basic module
> E85
via the general module
> E70, E93
via the footwell module (FRM)
- Switching on the hazard warning lights
> E60, E61, E63, E64
via the light module
> E85
via the light switch cluster
> E70, E93
via the footwell module (FRM)
- Sending emergency call (via telematics control unit)



Visual and audible seat belt warning
For the seat belt warning, the signals of the 2 seat belt buckle switches (driver's belt/front-passenger belt) are monitored separately.
If the seat occupancy detector detects that the passenger seat is occupied, the front passenger's belt must be inserted into the seat belt buckle. This switches off the seat belt warning.

The following situations are taken into account in respect of the issuing of a seat belt warning:
- Front seat belt not fastened and distance driven less than 200 m
If less than 200 m has been driven, only a visual seat belt warning is issued (the seat belt indicator lamp lights up). The vehicle may for example be driven out of a garage without triggering an audible seat belt warning.
- Front seat belt not fastened and distance driven more than 200 m
The seat belt indicator lamp and the check control symbol in the LCD light up (visual seat belt warning). The audible seat belt warning is activated for approximately 90 seconds.
Once the seat belt has been fastened, the visual seat belt warning disappears. The audible seat belt warning is deactivated.
If the seat belt has not been fastened by the end of the audible seat belt warning, the seat belt indicator lamp lights up.
- Unfastening the front seat belt when the vehicle is in motion
If a seat belt is unfastened when the vehicle is in motion, the seat belt warning lamp will light up immediately.
The check control symbol also lights up in the LCD after approx. 15 seconds. An audible seat belt warning sounds for approximately 90 seconds.
Once the seat belt has been fastened, the visual seat belt warning disappears. The audible seat belt warning is deactivated.
If the seat belt has not been fastened by the end of the audible seat belt warning, the seat belt indicator lamp lights up.



Emergency call
- Manual emergency call
A manual emergency call is initiated by the emergency call button. The emergency call button is directly connected to the telephone. A voice connection is established with the service provider by pressing the emergency button (press button for at least 2 seconds).
The manual emergency call function is not standard.
> E60, E61, E63, E64, E70, E93
The emergency call button is integrated into the roof control panel (FZD).
> E85
The emergency call switch is installed in the centre console.
- Automatic emergency call:
A further function is connected to the safety system on vehicles equipped with BMW Assist: the automatic emergency call In the event of an accident exceeding a certain level of severity, BMW Assist automatically initiates an emergency call. Some of the vehicle data and its exact location, which is determined by the navigation system, are transmitted to the emergency call centre.



Monitoring of battery cable
Petrol engine vehicles:
The battery cable must be monitored on vehicles where the battery cable is installed on the underbody parallel to the fuel line. The battery cable is monitored by the crash safety module.
Depending on the type of vehicle, the battery cable is made from copper or aluminium and insulated with plastic. The plastic insulation is covered by a low impedance metal braiding which serves as the monitoring wire. The battery cable is then covered with a second insulation layer made from plastic. This is the external insulation layer.
A connection wire is provided at both ends of the monitoring wire. Both connection lines are connected to the crash safety module.
The crash safety module triggers the safety battery terminal if the monitoring wire is damaged or there is a short to positive or negative. The battery cable is consequently separated from the battery.

Notes for service staff
- General note:
- Diagnosis:
- Encoding/programming:

National versions
The following national versions are described:

- US
- Japan/Gulf States



US national version
- Knee airbag
> E63, E64, E85, E93
When triggered, the knee airbag provides support for the knee if the front passenger is not wearing a seat belt. This initiates controlled forward displacement of the upper body. The upper body is cushioned by the respective airbag (driver's or passenger's side).
- Adaptive belt force limiter, front left and front right
> E70
The pyrotechnic belt force limiter minimises the load on the upper torso of the front-seat occupants in the event of a severe frontal collision. The risk of injury from the force of the seat belt acting on the body is reduced.
Two torsion shafts are fitted in the inertia reel. The torsion shafts are intermeshed. Up to a certain load, the belt force is specifically limited by the two torsion shafts. From a certain load, a gas generator is used to decouple the torsion shafts. Only one of the torsion shafts is connected to the belt. This allows the belt force to be smoothly limited for the entire duration of the impact.
- Seat position detector on the driver's side
> E70
According to the stipulations of the FMVSS (Federal Motor Vehicle Safety Standards), the driver's seat must be able to tell the difference between a 5% woman and a 50% man.
The seat position detector indicates the longitudinal position of the driver's seat. This allows the system to recognise the distance between the person sitting on the driver's seat and the steering wheel.
The seat position signal influences the response of the adaptive belt force limiter and the delayed triggering of the 2nd stage of the gas generator (driver's airbag).
The adjustment distance of the driver's seat is registered by Hall sensors in the drive and processed in the seat module. The seat module emits a message on the K-CAN. The crash safety module is a bus subscriber on the K-CAN.

Note: Recalibrate the driver's seat
Over time, repeatedly moving the driver's seat forward and back can cause the seat position to become implausible. When the driver's seat needs to be recalibrated, this will be shown by a Check-Control symbol and a Check-Control message.
Calibration is described in the vehicle Owner's Handbook.



- Emergency call
The manual emergency call and the automatic emergency call are standard features.
- Manual emergency call
(Same as Europe version)
- Automatic emergency call:
If the accident is of corresponding severity, the crash safety module sends a signal to the Telematics Control Unit (TCU). The TCU initiates an emergency call which also contains the location of the vehicle. The TCU receives the location determination for the navigation system. If a navigation system has not been installed, the location is determined by an internal GPS receiver in the TCU.
- Visual and audible seat belt warning
A visual and audible warning is triggered when terminal 15 is ON. The seat belt warning is active for a limited period of time (6 seconds).
The further progression of the seat belt warning is identical to that of the seat belt warning in Europe vehicles.



National version - Japan/Gulf States
- Visual and audible seat belt warning
A visual and audible warning is triggered when terminal 15 is ON. The seat belt warning is active for a limited period of time (6 seconds).

Subject to change.