Part 1

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





Introduction
The ACSM crash safety system is installed in E60, E61, E63, E64 from 09/05 (ACSM stands for "Advanced Crash Safety Module", referred to as the "crash safety module").
In contrast to the safety system used to date in the E60, E61, E63 and E64, E85, all crash safety functions are controlled by the crash safety module.

> E60, E61, E63, E64
[system overview ...]
> E70
from start of series production [system overview ...]
> E85
Launch date from 01/06 [system overview ...]
> E93
from start of series production [system overview ...]
The crash safety module has the following tasks:
- Detects an accident situation which could be critical for the occupants
- Activates the necessary restraint systems (selectively, depending on the severity and type of accident)

Brief description of components
The following sensors detect the direction and severity of an impact:

- Sensors in the crash safety module
The following sensors are installed in the crash safety module:
- 2 acceleration sensors for longitudinal and transverse acceleration
- 1 yaw-rate sensor to detect vehicle rollover (E64, E70, E93)
- 2 acceleration sensors for transverse acceleration and acceleration about the vertical axis for detecting rollover (E64, E70, E93 only)
- Airbag sensor in B-pillar, driver's and passenger's side
The 2 airbag sensors in the left and right B-pillars each feature one transverse acceleration sensor and one longitudinal acceleration sensor. The sensors are arranged at 90 degrees to each other.

- Front airbag sensor, driver's side and front-passenger side
The 2 front airbag sensors are longitudinal acceleration sensors.
The installation of the front airbag sensors depends on the national version.
> E60, E61, E63, E64, E85, E93: US version only
> E70: Europe and US versions

- Airbag sensor on front driver's side door and front passenger's side door
The 2 airbag sensors are pressure sensors.
The installation of the airbag sensors depends on the national version.
> E60, E61, E63, E64: standard
> E70, E85: US version only
> E93: Europe and US versions

The following components send signals to the crash safety system:
- Seat belt buckle switch for driver's seat belt and passenger's seat belt
The seat belt buckle switches provide information as to whether or not the seat belts are buckled.
The crash safety module powers the seat belt buckle switches.
The power consumption of the switch forms the signal for the switch position (seat belt engaged or not engaged). The signal from the seat belt buckle switch decides whether or not the seat belt tensioner is actuated when needed.
The seat belt-lock switches on the driver and front passenger seats are permanently monitored when terminal R is ON.
- Seat-occupancy detector, driver's side
> Only vehicles with option 5DF "Active cruise control with stop & go function".
The seat-occupancy detector for the driver's side is only used to control the system (active cruise control with stop & go function) (e.g. if the driver intends to get out of the vehicle).
If the driver's seat is occupied, the seat occupancy mat changes its resistance. The signal is sent to the crash safety module via a direct wire.
The crash safety module emits this signal as a message on the K-CAN.
- Passenger-seat occupancy detector
The passenger seat-occupancy detector recognises whether the seat is occupied or not. The resistance of the seat occupancy mat changes when it is loaded with a weight of more than approx. 12 kg. The signal is sent to the crash safety module via a direct wire.
If the front passenger seat is recognised as being occupied without the seat belt buckle switch sending a signal, a fasten belt warning will be emitted.
> - E60, E61, E63, E64, E85, E93
The seat-occupancy detector is used for triggering the airbags and for the seat belt warning.
If the crash safety module triggers the airbags and the front passenger seat is unoccupied, the front passenger's airbag and the side airbag on the front passenger side will not be triggered.
The head airbag is triggered.
> - E70
The seat-occupancy detector is only used for the seat belt warning.
If the crash safety module triggers the airbags and the front passenger seat is unoccupied, the front passenger's airbag, and the side airbag and head airbag on the front passenger side will not be triggered.
Whether or not the belt tensioner on the front passenger side is activated depends on the status signal of the seat belt buckle switch (seat belt fastened or not fastened). The seat belt tensioner is also triggered if the seat belt is inserted in the seat belt buckle switch (only in the case of head-on/rear-end impact).

- Passenger seat occupancy detector (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 side are automatically deactivated (front-passenger airbag and side airbag). The indicator lamp for front-passenger airbag deactivation lights up.
The seat-occupancy detector is based on an evaluation of the surface pressure generated when the seat is loaded.

- Switch for disabling front passenger's airbag (Europe version)
If option 470 "ISOFIX mounting for child seat" (front) has been installed, the airbags can be disabled via the switch for passenger's airbag deactivation. The switch is operated using the key integrated into the remote control.
In switch position OFF, the following airbags on the front-passenger side will not be triggered: front-passenger airbag and side airbag.
The indicator lamp for front-passenger airbag deactivation (front-passenger airbag OFF lamp) lights up.
> E60, E61: The switch is located in the glove compartment.
> E63, E64, E70, E85, E93: The switch is installed on the instrument panel on the passenger's side.

Note: Retrofit of the passenger's airbag disabling facility
For vehicles without a switch to deactivate the front-passenger airbag, there is a retrofit kit (option 5DA "front-passenger airbag deactivation" or option 470 "ISOFIX child seat mounting").

- Battery cable monitoring wire
Gasoline 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 crash safety module triggers the safety battery terminal in the case of a short-circuit.
The following control units are involved in the crash safety system:
- ACSM: Crash safety module
All inflator assemblies and sensors are connected directly to the crash safety module.
The crash safety module evaluates the data from the sensors.
In the case of a crash, the crash safety module decides whether it is necessary to trigger the seat belt tensioner and airbags and what airbags need to be triggered.
The crash safety module also triggers the active head restraints (only E60, E61 and E70 from 09/07).
> E60, E61, E63, E64, E85
> E70, E93
- CAS: Car access system
The CAS control unit provides input signals relating to terminal voltage (e.g. terminal R ON). The CAS control unit is the master control unit for the central locking system. (KGM, KBM and JBE are the executing control units for the central locking.)
- DME or DDE: Digital engine electronics or digital diesel electronics
When an airbag is triggered, the electric fuel pump is switched off by the DME or DDE (only on vehicles with no electronic control of the fuel pump).
- EKP: Controlled fuel pump
When an airbag is triggered, the electric fuel pump is switched off by the EKP control unit (only on vehicles with electronic control of the fuel pump).
The EKP control unit receives a message from the crash safety module.
- GM: General module
> E85
The general module provides input signals relating to terminal voltage (e.g. terminal R ON). The general module is the executing control unit for the central locking system. The general module controls the interior lighting. In the event of an accident with corresponding severity, the interior light switches on automatically and the central locking unlocks.
- KOMBI: Instrument cluster
The instrument cluster provides a visual seat belt warning and triggers an audible seat belt warning.
The crash safety module controls the seat belt warning using a check control message.
The instrument cluster receives data about the status from the crash safety module when terminal R is ON. Depending on the status, the optical and audible warning is triggered when terminal 15 is ON.
- KGM: Body gateway module
> E60, E61, E63, E64
The KGM is the data interface (= the gateway) between the K-CAN and the PT-CAN. (K-CAN = body CAN; PT-CAN = powertrain CAN.)
The KGM is connected to the crash safety module via the K-CAN.
The KGM is the executing control unit for the front central locking system. (The CAS control unit is the master control unit for the central locking system. )
The KGM controls activation of all front central locking drive units.
In the event of an accident exceeding a certain severity (crash signal from crash safety module) the front central locking is automatically unlocked.
- KBM: Basic body module
> E60, E61, E63, E64
The KBM is connected to the crash safety module via the K-CAN.
The KBM is the executing control unit for the rear central locking system. (The CAS control unit is the master control unit for the central locking system. )
The KBM controls activation of all rear central locking drive units.
The KBM controls the interior lighting. In the event of an accident exceeding a certain severity (crash signal from crash safety module) the interior light is automatically switched on and the rear central locking is unlocked.
- JBE: Junction box electronics
> E70, E93
The JBE is connected to the crash safety module via the K-CAN.
The JBE is the executing control unit for the central locking system. (The CAS control unit is the master control unit for the central locking system. )
- LM: Light module
> E60, E61, E63, E64
The lights module is connected to the crash safety module via the K-CAN. In the event of an accident exceeding a certain severity (crash signal from crash safety module) the light module will switch the hazard warning lights on.
- LSZ: Light switch cluster
> E85
The light switch cluster is connected to the crash safety module via the K-bus. In the event of an accident exceeding a certain severity (crash signal from crash safety module) the light switch cluster will switch the hazard warning lights on.
- FRM: Footwell module
> E70, E93
The footwell module is connected to the crash safety module via the K-CAN. In the event of an accident exceeding a certain severity (crash signal from crash safety module) the footwell module will switch the hazard warning lights on.
- SMFA and SMBF: Driver's seat module and front passenger's seat module
> E64, E93
Seats with three-point seat belt integrated in the backrest are installed in the cabriolet. If the seat backrests are not locked correctly, in the event of an accident there is the danger that the occupants move forward with the backrests with no restraint.
The seat modules monitor the seat backrest to ensure they are locked correctly. Hall sensors are installed in the seat backrests for this purpose.
> - E64
The seat modules send messages on the K-bus to the centre console switch cluster (SZM) when the seat backrests are not locked correctly. The SZM is the data interface (= gateway) to the K-CAN. The SZM processes the message (check control message).
> - E93
If the backrests are not correctly locked, the seat modules will emit messages on the K-CAN.
The check control messages are shown in the instrument cluster and in the central information display.
The check control message is triggered as follows:
- The seat belt indicator lamp in the instrument cluster comes on (visual seat belt warning).
- The check control symbol is shown in the LCD display.
- The check control messages relating to the check control symbol are shown in the Central Information Display (CID).
The crash safety module controls the following components:
- Triggering circuit for the airbags
With the maximum amount of equipment, the safety system consists of the following triggering circuits:
- Driver's airbag (stage 1)
- Front-passenger airbag (stage 1)
- Driver's airbag (stage 2)
- Front-passenger airbag (stage 2)
- Side airbag, front driver's side
- Side airbag, front-passenger side
- Side airbag, rear driver's side
- Side airbag, rear passenger side
- Head airbag, driver's side
- Head airbag, front-passenger side
- Seat belt tensioner, driver's seat belt
- Seat belt tensioner, front passenger's seat belt
- Seat belt tensioner, rear driver's side
- Seat belt tensioner, rear passenger side
- End fitting pretensioner, driver
- Knee airbag for driver or active head restraint for driver
- Knee airbag for front passenger or active head restraint for front passenger
- Adaptive belt force limiter, front left
- Adaptive belt force limiter, front right
- Safety battery terminal



Driver and front-passenger airbag
The driver and front-passenger airbag reduces the risk of injury to the occupants' head and chest area in the event of a head-on collision.
The driver airbag is located under the centre pad on the steering wheel. The front-passenger airbag is integrated into the instrument panel above the glove box.
Side airbag
Side airbags reduce the risk of injury to the occupants' pelvis and torso in the event of a side impact. The side airbags are installed behind the respective door trim panels.
Head airbag
> E60, E61, E63, E70
The head-level airbag prevents the head making direct contact with the side structure or an object which penetrates the vehicle. The head airbag extends continuously from the A-pillar to the C-pillar.
The shape and stability of the head airbag are retained for several seconds after triggering. The head airbag deflates slower than the front and side airbags, thus providing longer protection for the head in lateral rollover situations.
A head-level airbag is installed on the driver's side and on the front passenger's side.
Belt tensioners
As a rule, the seat belt will not be sitting completely tight around the body: This seat belt slack makes sure that the occupants have adequate comfort of movement.
During a head-on or rear-end collision, the pyrotechnical seat belt tensioner pulls down the seat belt buckle by several centimetres, thus pulling the seat belt tight into the occupant's shoulder and pelvis.
> E64, E70, E93
The seat belt tensioner also triggers in the event of imminent rollover.
End fitting pretensioner
> E60, E61, E70 Europe version
The end fitting pretensioner prevents the driver's pelvis moving too far forward in the event a head-on or rear-end collision. The end fitting pretensioner is installed in addition to the seat belt tensioner on the driver's seat. In principle, the end fitting pretensioner functions in the same way as a seat belt tensioner.
Active head restraint
> E60, E61
> E70 from 09/07
On triggering, the active head restraint locks the distance between the head restraint and head in order to reduce the load on the cervical vertebrae during a rear-end collision.
(Reason: The distance between the head and head restraint can increase as the result of the individual setting options of the comfort seat.)
The plunger extends when the inflator assembly in the backrest is triggered. The plunger operates the bolt of the active head restraint. As a result, the head restraint is guided forward on a slide guide.
Safety battery terminal
Depending on the severity of the accident, the safety battery terminal disconnects the starter motor and the alternator from the battery. This minimises the risk of electrical short-circuits in a serious accident.
- Airbag indicator lamp
The airbag indicator lamp indicates the operability of the crash safety system. The airbag indicator light in the instrument cluster is actuated as follows by the crash safety module:
> E60, E61, E63, E64, E70, E93: via the K-CAN
> E85: via the K-bus
- Seat belt indicator lamp
The seat belt indicator lamp is the visual seat belt warning. The visual seat belt warning instructs the occupants of the vehicle to fasten their seat belts. Terminal 15 ON activates the visual seat belt warning.
The visual seat belt warning is issued as follows:
- Seat belt warning lamp in the instrument cluster
- Check control symbol in LCD display in instrument cluster
- Indicator lamp for front passenger's airbag deactivation
If the warning lamp for passenger-airbag deactivation (passenger airbag off lamp) is lit, the following airbags on the passenger side have been deactivated: front-passenger airbag and side airbag.
The passenger airbag OFF lamp is constantly monitored by the crash safety module. A fault in the power supply or a defective lamp is stored in the fault memory of the crash safety module. If this occurs, the airbag warning lamp is switched on.
- Rollover protection controller and roll bar
> Only E64, E93
The rollover protection system triggers in the event of the vehicle rolling over or in situations that could lead to the vehicle rolling over. The rollover system consists of the rollover protection controller and 2 extendable roll bars.

- Fuel pump
Depending on accident severity, the fuel supply may also be cut off.
- TCU: Telematics control unit
The emergency call is transmitted via the TCU. The TCU is connected to the crash safety module by the instrumentation bus (I-bus).
Mechanical components of the safety system:
- Belt force limiters on seat belts
The seat belts are the primary restraint system for all occupants.
To minimise the load on the chest area of the front passengers in the event of a severe head-on collision, the front seat belts are fitted with belt force limiters as standard. The belt force limiters ensure that the belt strap can give by ay defined amount if the load exceeds a certain level. The risk of injury due to the belt force acting on the body is therefore reduced.

Continued in Part 2