Table of Contents E70 Advanced Crash Safety Module (ACSM) Subject Page Introduction .4 Advanced Crash Safety M odule ACSM .4 Schematic Circuit Diagram ACSM E70.6 Functions.8 Basic Tasks of ACSM .8 Crash-Relevant Functions .8 Evaluating the SensorSignals.9 Detecting a Crash and Determining the Triggering Times and the Order.10 Triggering the Output Stages of the Firing Circuits .10 Outputting the Crash Telegram .11 Crash Entries .11 Emergency Call Functions.12 Automatic Emergency Call .12 Breakdown Call .12 Manual Emergency Call.12 Rollover Protection System .13 Rollover Detection.13 Functional Principle of the Yaw Rate Sensor.15 Seat Position Detection .16 System Monitoring Functions.16 System Self-test (pre-drive check).16 Cyclic M onitoring.17 Indication of System Operability .17 Fault Indication and Fault Storage .17 Fault Output (diagnosis).17 Seat Belt Reminder Function .17 Deactivation of SBR Function.19 Deactivation of Passenger Airbags.19 Passenger Airbag OFF Light.19 0C3 Mat .20 Initial Print Date: 10/06 Revision Date: Subject Page System Components.22 Crash Safety M odule .22 Sensors and Switches .23 B-Pillar Satellite.23 Digital Data Transmission by Means of Current Interface.24 Up-Front Sensors.24 Door Pressure Sensors .24 OC3 Mat .25 Emergency Call Button .25 Seat-Belt Buckle Switches.25 Actuators.26 Front Airbag, Driver.27 Front Airbag, Passenger.27 Curtain Airbag .28 Side Airbag .29 Front Seat Belt Pretensioner.29 Adaptive Seat Belt Force Limiter.30 Adaptive Seat Belt Force Limiter Positive Engagement.30 Adaptive Seat Belt Force Limiter Non-Positive Engagement .31 Safety Battery Terminal .31 Service Information.32 General Safety Regulations.32 Crash Safety M odule .32 B-pillarSatellite .32 Advanced Crash Safety Module Model: E70 Production: From Start of Production IBIICT1UIS After completion of this module you will be able to: • Describe the different functions of the ACSM on the E70. • Identify the components that comprise the ACSM ontheE70. • Diagnose functions of the ACSM system on the E 70. • Service components on the ACSM system used on the E70. 3 E70 Advanced Crash Safety Module Introduction Advanced Crash Safety Module ACSM The safety system ACSM is used in the E70.The task of ACSM is to detect accident situations critical forthe vehicle occupants and to activate the necessary restraint sys¬ tems selectively corresponding to the crash severity. The crash safety module performs internal diagnosis and monitors all inputs and out¬ puts. Any faults that may occur are stored nonvolatile in the crash safety module and indicated to the driver by way of the airbag indicator lamp in the instrument cluster. Communication with other control units in the vehicle's system network takes place via the K- CAN and the F-CAN. In the event of a crash, a K-bus telegram is trans¬ mitted (provided a telephone is installed) via an additional separate data line to the Telematics Control Unit (TCU) and the emergency call trig¬ gered (depending on national version). It is possible to encode the crash safety module via the K- CAN. Diagnosis of the crash safety module takes place via the diagnosis CAN to the gateway that is located in the J unction-box ECU on the E70. 4 E70 Advanced Crash Safety Module F-CAN Signals atACSM Control Unit In/Out Signal Source Function IN Vehicle Speed Wheel Speed Sensors Dynamic Stability Control DSC Information for recognizing possible rollover situation IN YAW Rate Dynamic Stability Control DSC Information for recognizing possible rollover situation IN Steering angle Steering angle sensor Steering column switch cluster Information for recognizing possible rollover situation 5 E70 Advanced Crash Safety Module Schematic Circuit Diagram ACSM E70 6 E70 Advanced Crash Safety Module Index Explanation 1 Up-front sensor, left 2 Head airbag, front passenger's side 3 Footwell module FRM 4 Instrument cluster 5 Car Access System (CAS) 6 J unction-box ECU 7 Switch for passenger airbag deactivation 8 Up-front sensor, right 9 Head airbag, driver's side 10 Door pressure sensor, right 11 F rant passenger airbag, 2-stage 12 Adaptive seat belt force limiter, right 13 ACSM ECU 14 Front passenger's seat 15 B - pillar satellite, right 16 Safety battery terminal 17 Main power connection to starter and alternator 18 Ground 19 Telephone 20 Seat belt pretensioner, left 21 Seat belt pretensioner, right 22 Side airbag, right 23 Side airbag, left 24 Anchor-fitting pretensioner 25 Seat occupancy detector 26 Power supply, seat occupancy detector 27 Seat occupancy detector (SBE for EU), front passenger 28 Seat occupancy detector (SBE forEU), driver 29 Seat belt buckle switch, driver 30 Seat belt buckle switch, front passenger 31 Ground point 32 Driver's seat 33 B-pillar satellite, left 34 Adaptive seat belt force limiter, left 35 Door pressure sensor, left 36 Driver's airbag, two-stage 37 Steering column switch cluster SZL 38 Indicator lamp for passenger airbag deactivation K-CAN Body CAN K-Bus Body Bus KL R Terminal R 7 E70 Advanced Crash Safety Module Functions Basic Tasks of ACS M The task of advanced crash safety module is to evaluate permanently all the sensor sig¬ nals in orderto identify a crash situation. As a result of the sensor signals and their evalu¬ ation, the crash safety module identifies the direction of the crash and the severity of the impact. Also included is information on the occupants and whetherthey have their seat belts fastened or not. From this information, measures are taken to selectively trigger the nec¬ essary restraint systems. The ACSM monitors itself at all times and indicates that the system is in standby mode by the airbag indicator lamp briefly going out after every "igni¬ tion ON" status. If a fault occurs during operation, it is indicated by the airbag indicator lamp and is additionally stored in the fault code memory. This fault code memory can be read out for diagnostic purposes. In the event of a crash, this is communicated to the other users in the bus-system net work by way of a bus telegram. The relevant control units respond to this telegram by executing their own activities. These activities include: • Opening the central-locking system • Activating the hazard warning flashers • Switching on the interior lights • Deactivating the fuel pump • Switching off the alternator • Automatic emergency call Anotherfunction of ACSM is the seat belt reminderfunction, which uses optical and acoustic signals to remind the driver and front passengerto fasten their seat belts. C rash- Relevant Functions The crash safety module mustfulfill the following crash-relevant functions: • Evaluating the sensor signals • Detecting a crash and determining the triggering times and the order • Triggering the output stages of the firing circuits • Output of a crash telegram for other users in the communication system network 8 E70 Advanced Crash Safety Module Crash entries Emergency call functions Driver's seat position recognition Evaluating the SensorSignals The crash safety module incorporates a longitudinal acceleration sensor and a transverse acceleration sensor. The sensors serve to detect and verify front-end, side-on and rear- end crashes. The crash safety module additionally contains a sensorfor rollover detection. This func¬ tion has been adopted from the E64 and activates the curtain airbag and the seat belt pretensioners in the E70. Satellites are installed at the B-pillars. T he satellites each consist of a longitudinal acceler¬ ation sensor and a transverse acceleration sensor. Together with the transverse acceleration sensor in the crash safety module, the trans¬ verse acceleration sensors serve to detect side-on crashes. Together with the longitudinal acceleration sensor in the crash safety module, the longitu¬ dinal acceleration sensors serve to detect front-end and rear-end crashes. Sensors in the E70 9 E70 Advanced Crash Safety Module The acceleration sensors measure the positive acceleration (+) and the negative acceler¬ ation (- / deceleration) in the X and Y directions. The resultant from the xand y signals is the definitive factor in determining the direction of the impact. Note: US vehicles have additional up-front sensors and door pressure sensors. Detecting a C rash and Determining theTriggering Times and the Order The crash safety module uses the values transmitted by the sensors to determine the direction and severity of the crash. The threshold values of two independent sensors must be detected simultaneously in orderto detect a crash. In the case of a front end crash, for example, the acceleration val¬ ues from the B-pillar satellite and from the longitudinal-acceleration sensor must be detected in the crash safety module. Based on the crash severity and direction, an algorithm determines the triggering (firing) points and the order of the restraint systems to be activated. Triggering the Output Stages of the Firing Circuits The firing-circuit output stages are only triggered if the corresponding thresholds are detected by two different sensors simultaneously, for example the B-pillar satellite and the crash safety module. From "Terminal RON" the crash safety module is supplied with power by the Car Access System CAS and is ready for operation on completion of the system selftest. The firing capacitors, which also serve as an energy reserve, are charged up by a switching con¬ troller. The firing capacitors provide the firing energy in the event of a crash even if the power supply is interrupted as the result of the crash. The output stages of the firing circuits consist of a high-side and a low-side power circuit breaker. The high-side power circuit-breaker controls the firing voltage, while the low-side power circuit-breaker switches to ground. The output stages of the firing circuits are con¬ trolled by the microprocessor. The high-side and low-side power circuit breakers also serve the purpose of checking the firing circuits during the system self-test. 10 E70 Advanced Crash Safety Module Outputting the C rash Telegram In the event of a crash involving triggering of the restraint systems, the crash safety module sends a crash telegram to the users in the bus-system network. As a result, the respective control units perform the following functions corresponding to the crash severity: Function ECU S hut down electric fuel pump (as from 6-cylinder and diesel engines) Electric fuel pump (EKP) module Shutdown electric fuel pump on 4-cylinder engines DM E Switch off alternator DM E Open central locking J unction-box ECU Switch on hazard warning lights Footwell module Switch on interior lights Footwell module M ake emergency call Telematics control unit Crash Entries In the event of a crash where one or more actuators are triggered, a crash entry is stored in a non-erasable memory. After three crash entries, a non-erasable fault entry is stored in the fault memory with the instruction to replace the crash safety module. The three crash entries could also be stored during the course of an accident. Each crash entry is assigned a system time. The control unit remains capable of firing even afterthree crash entries. The crash entries cannot be erased and serve the purpose of subsequent device diagno¬ sis. A maximum of three crash entries can be stored. The control unit must then be replaced. 11 E70 Advanced Crash Safety Module Emergency Call Functions A manual and an automatic emergency call is provided as standard on US vehicles. Furthermore, the driver has the option of activating a breakdown call. Irrespective of whetherthe customer orders a telephone or not, each vehicle is equipped with a telemat¬ ics control unitTCU, a telephone antenna, a hands-free kit as well as a GPS antenna for determining position. Automatic Emergency Call The crash safety module sends a crash telegram to theTCU in the event of a crash of corresponding crash severity. TheTCU places an emergency call, which at the same time contains the location of the vehicle. Parallel to this, attempts are made to set up a voice connection with the vehicle occu¬ pants to obtain more information on the accident (severity of the accident, number of injured) so that further rescue operations can be initiated. Breakdown Call The breakdown-call button in the E70 ora menu button in the central information display is used to establish a connection with the BMW Emergency Service in the relevant coun¬ try. Manual Emergency Call The emergency-call button is located in the roof console. The emergency- call button is connected directly to the TCU. Pressing the emergency-call buttons establishes a voice connec¬ tion with the relevant country provider. The voice connection is indicated by a flashing LED in the switch. Emergency call button in roof functions center E70 12 E70 Advanced Crash Safety Module Rollover Protection System The rollover protection system is an important instrument for improving occupant protec¬ tion in the event of the vehicle rolling over. The seat belt pretensioners and the curtain airbags are triggered in response to corresponding crash severity. There are different factors which can cause a carto overturn or roll over. The most com¬ mon causes are: • The vehicle leaves the road. One side of the vehicle digs into a roadside ditch and the vehicle rolls over. • The car hits a ramp (a crash barrier) on one side. The car rotates about its longitudi¬ nal axis as a result of the high angular velocity. • The car skids sideways off the road surface and buries itself with its wheels in the soft soil. The kinetic energy could be sufficient to upend and overturn the car. • The car skids sideways off the road into the curb and is upended. The crucial factors which determine whetherthe car overturns are not just the angle but also the angular velocity at which the car is set into the roll. All these vehicle movements can also occur after a front-end, side-on or rear-end crash. Rollover Detection The module incorporates a special sensor system for detecting rollover situations. Besides the two sensors for longitudinal (x-axis) and transverse acceleration (y-axis), there is a yaw-rate sensor and a Low-g sensorforthe z-axis and for the y-axis. In addition to its own measured values, the crash safety module constantly receives information from the DSC relating to the current driving characteristics of the vehicle. This information serves to meet the demanding requirements relating to the triggering times. The longitudinal and transverse acceleration sensors registerthe positive and negative vehicle acceleration in a measuring range of O-lOOg. They serve to detect elevated accel¬ eration and deceleration in a crash. The two Low-g sensors have a narrow measuring range from 0-2g and can precisely detect low levels of acceleration and deceleration when, for example, the vehicle skids lat¬ erally off the road and buries itself with its wheels in the soft soil. 13 E70 Advanced Crash Safety Module Crash Detection E70 T Index Explanation Index Explanation 1 Crash safety module 6 Curtain airbag, front passenger 2 Rollover sensor 7 Dynamic stability control DSC 3 Low-g-sensors (z-/y-axis) 8 Seat belt pretensioner, driver 4 Longitudinal and transverse acceleration sensors 9 Curtain airbag, driver 5 Seat belt pretensioner, front passenger 10 Safety battery terminal The sensors provide a voltage as measured variable. This voltage is a measure forthe acceleration and is converted directly into digital signals in the sensor. The digital values are sent to the processor in the crash safety module for evaluation. The processor evalu¬ ates the signals from the longitudinal and transverse acceleration sensors and the two Low-g sensors. The signals of the yaw rate sensor are also included in the calculation. The results are compared with the stored algorithm. If the processor detects that a rollover situation is imminent, it will triggerthe seat belt pretensioners and the curtain airbags. 14 E70 Advanced Crash Safety Module Functional Principle of the Yaw Rate Sensor A yaw rate sensor is used for detecting rollover situations. The yaw rate sensor has a comblike structure. It consists of a fixed comb structure (3) and a rotational oscillator (2) with amoving comb structure. Together, the comb structures form a capacitor. The rota¬ tional oscillator is fitted on bearings on a shaft (1) in its center. Index Explanation 1 Rotational axis 2 Rotational oscillator 3 Fixed comb structure When the vehicle is in a horizontal position, the rotational oscillator turns within the comb structure and detects the change of direction (left/right). If the vehicle is brought into a tilt¬ ing position (on a slope), the rotational oscillator is moved out of the comb structure.S This causes a change in capacity, which in turn creates a change in voltage proportional to the deflection of the rotational oscillator in the mV range, which is evaluated as the measured variable. The voltage change is directly related to the angle and, in the same way, the speed of the voltage change is directly related to the angle velocity.The angle and the angle velocity are the measurements used for the algorithm calculation. The voltage values are directly converted into digital values in the yaw rate sensor and sent to the main processorfor evaluation. 15 E70 Advanced Crash Safety Module Seat Position Detection Adaptive or intelligent restraint systems are developed with the aim of optimizing the pro¬ tection offered by the restraint system under changing conditions. Besides the crash severity, the seated position and posture of the occupant are important factors in calculat¬ ing the triggering procedures. A seat position recognition facility is used on the driver's side in the E70 forthe purpose of distinguishing persons in terms of their body size. The task of the seat position recog¬ nition facility is to distinguish between a relatively small person and a normal sized person within the forward/backward adjustment range of the seat. This recognition function is a further technical feature designed to increase occupant safety. The characteristics of the adaptive seat belt force limiter is correspondingly adapted to the driver's seat position. In accordance with US legislation (FM VSS208) a facility for recognizing the size of per¬ sons must be provided on the driver's seat. This size recognition facility is based on the adjustment range of the forward/backward seat adjustment facility. On the E 70, the exact position is determined by the actuator motor in the driver's seat. A detailed description of the functional principle of the position detection system can be found in the Product Information "Seats" System Monitoring Functions The crash safety module must execute the following system monitoring functions: System self-test (pre-drive check) Cyclic monitoring Indication of system operability Fault indication and fault storage Fault output (diagnosis) Seat belt reminderfunction • Deactivation of passenger airbags System Self-test (pre-drive check) ACSM performs a system self-test as from "Terminal R ON". The airbag indicator lamp is activated for about. 5 s during the system self¬ test. When the system self-test is concluded and no fault has been found, the airbag indicator lamp goes out and the system is ready for operation. 16 E70 Advanced Crash Safety Module TEW *4 794 Cyclic Monitoring Once the system self-test has been successfully concluded and the system is ready for operation, a cyclic monitoring procedure is performed forfault monitoring purposes. Cyclic monitoring serves the purpose of internal diagnosis of the ECU and the overall airbag system. Cyclic monitoring is carried out for as long as the system is at "Terminal R ON". Indication of System Operability ACSM system operability is indicated by the airbag indicator lamp going out in the instru¬ ment cluster. Fault Indication and Fault Storage The crash safety module has a non-volatile fault memory. The airbag indicator lamp indi¬ cates any entry in the fault memory. A distinction is made between internal and external faults when entering the fault code. Events such as triggering of the airbag or seat belt pretensioner are also stored in the fault memory. Note: The entry of a triggered restraint system in the fault memory does not mean that the restraint system was defective in the crash situation, rather it only means that the restraint system is not available for further triggering. Fault Output (diagnosis) With the aid of the diagnostic tools (DIS plus, GT1), the fault memory can be read out via the diagnosis interface. After rectifying the faults or after replacing the triggered components, the fault memory can be cleared with the diagnosis command "Clearfault memory". Seat Belt Reminder Function All vehicles with ACSM have a Seat Belt Reminderfunction (SBR) as standard.The SBR function detects whetherthe driver and front passenger have fastened their seat belts. If not, a corresponding indicator reminds them to fasten their seat belt. Both seat belt buck¬ le switches are monitored separately. If the seat belt is not worn orthe seat belt is unbuckled while driving at a speed in excess of about. 8 km/h, a corresponding audible and visual warning is given. 17 E70 Advanced Crash Safety Module The seat belt warning is given by: • Fixed seat belt indicator lamp (seat belt symbol) • Variable seat belt indicator lamp (Check Control message) • Audible warning provided by the gong • Check control text message on vehicles with central information display Note: If with terminal 15 the seat belt contact on the driver's side is not closed, an audible warning is triggered and the seat belt warning lamp activated for 6 seconds. The SBR function is subdivided into two phases. The first phase is the initialization, monitoring and warning begin with the vehicle station- ary.The gong is additionally activated intermittently for maximum 90 s or until the seat belt is fastened. At the same time, the check control indicator is activated with the vari¬ able indicator lamp with the seat belt warning symbol for max. 23 s. On vehi¬ cles with the central information dis¬ play, a text message "Fasten seat belt" is additionally displayed. If the driver/front passenger does not fasten their seat belt within this period of time, the variable indicator lamp and the text message will go out after 23 s and the gong will switch off after 90 s. The fixed seat belt indicator lamp in the instrument cluster remains on until the seat belt is fastened. The second phase involves monitoring while driving, i.e. the system monitors whetherthe occupants have their seat belts fastened during vehicle operation.If the front passenger seat is detected as occupied, the front passenger switch must also detect that the pas¬ senger seat belt is fastened so as not to trigger a warning. A visual and audible warning is triggered 15 s after unbuckling the seat belt while driving. The gong is activated intermit¬ tently for maximum 90 s or until the seat belt is fastened again. At the same time, the vari¬ able indicator lamp with the seat belt warning symbol is activated for max. 23 s.The fixed indicator lamp remains active until the seat belt is fastened again. On vehicles with the central information display, a text message "Fasten seat belt" is additionally displayed for maximum 23 s. Note: If a warning was given for more than 90 s, the SBR function is not activat¬ ed again until the seat belt has been fastened and unbuckled again. 18 E70 Advanced Crash Safety Module Deactivation of SBR Function The SBR would constantly trigger an alarm customers who predominantly use the vehi¬ cle alone and transport objects on the front passenger's seat, like a briefcase, laptop etc. For such cases, the customer has the option of having the SBR function disabled in the workshop.The SBR function forthe front passengerside can be disabled with the coding option. In this case, only the audible warning, check control and text messages if applica¬ ble are suppressed. The seat belt mannikin in the instrument cluster remains on. Deactivation of Passenger Airbags The front and side passenger airbags must be disabled when a child seat is mounted on the passenger's side. Deactivation and activation of the front passenger airbags is the responsibility of the driver. Note: In US vehicles the law requires that a child seat tested to specifications (NHTSA FMVSS 208) with a child approximately one year old on the front passenger seat be automatically detected and the passengerairbags be deactivated. When a child restraint system holding a small child tested in accordance with NHTSA FMVSS 208 is used, the law in the USA requires that this be automatically detected and the front passengerairbags deactivated. In order to meet legislative requirements, the step was taken to replace the seat-occupancy detector (SBE) with an intelligent Occupant Classification (0C)facility. Passenger Airbag OFF Light The passenger airbag OFF lamp is located at the front of the roof functions center FZD next to the interior lights. The passenger airbag OFF lamp is activated and lights yellow when the passenger's front airbag and the side airbag on the passenger's side are deactivated. The brightness of this light is controlled by auto¬ matic regulation of the display lighting. 19 E70 Advanced Crash Safety Module 0C3 Mat The 0C3 mat (Occupant Classification) detects a child seat tested in accordance with NHTSA on the basis of the pressure per unit area and disables the passenger airbag. The OC3 mat consists of conductors in a pressure-sensitive resistance grid, so-called FSR elements (Force Sensitive Resistance).The conductors are connected to the elec¬ tronic evaluation unit. The FSR elements are wired in such a way that they can be sampled individually. When The mechanical load on a sensor element increases electrical resistance decreases and the measurement current changes accordingly. By analyzing the signals from the individual sensors, the analyzer can map the occupan¬ cy of the seat surface and identify local con¬ centrations of weight. The relationship between the areas and the load points indi¬ cates whetherthere is a person ora child seat holding a small child present. OC3 MatE70 Index Explanation A Surface imprint of a person B Surface imprint of a child seat 20 E70 Advanced Crash Safety Module Block diagram of an 0C3 mat E 70 U ® 3 Index Explanation Index Explanation 1 FSR elements 3 Electronic evaluation unit 2 Output monitoring 4 Input monitoring The electronic evaluation unit of the 0C3 mat sends a telegram via a separate K-bus to the crash safety module. The front passenger airbags (front and side airbags) are disabled when a child seat with small child is detected. The crash safety module activates the pas¬ senger airbag OFF indicator lamp in the roof functions center. Note: The front passenger airbags are not deployed when the front seat is not occupied. However, this is not indicated by the Passenger Airbag OFF light. 21 E70 Advanced Crash Safety Module System Components Crash Safety Module The advanced crash safety module essentially comprises the following components: • Crash safety module • Sensors and switches • Actuators The crash safety module is located centrally on the transmission tunnel in the vehicle. The crash safety module consists of a die cast housing with integrated plug cover. The crash safety module contains various sensors: • Rollover sensor • Low-g sensors • Longitudinal and transverse acceleration sensors The advanced crash safety module has a comprehensive sensor system. Transverse acceleration sensors in the B-pillarand door pressure sensors are used forthe purpose of side-on crash detection. The B-pillar satellites also have longitudinal acceleration sen¬ sors for front- and rear-end crash detection. Note: The crash safety module is located on the transmission tunnel behind the hand brake. Various sensors (rollover, Low-g as well as longitudinal and transverse acceleration sensors) are integrated in the crash safety module and the crash safety module is integrated in the K-C AN. 22 E70 Advanced Crash Safety Module Sensors and Switches In addition to the two sensors in the crash safety module, the system makes further use of the following sensors and switches to evaluate the crash severity and the correspond¬ ing triggering strategy: • B-pillar satellites • Up-front sensor • Door pressure sensor • OC3 Mat • Seat belt buckle switches • Airbag switch • Emergency call button The acceleration sensors measure the positive acceleration and the negative acceleration (deceleration) in the X and Y directions.The resultant from the X and Y signals is the defini¬ tive factor in determining the direction of the impact. The B-pillar satellites serve the purpose of detecting front-end, side-on and rear-end crashes. The B-pillar satellites on the left and right are of identical design and are allocated by way of mechanical coding during installation. B-Pillar Satellite The B-pillar satellite consists of a longitudinal acceleration sensor and a transverse accel¬ eration sensor. Index Explanation 1 Mounting points 2 Mechanical coding 3 Connection for cable plug Note: Externally, the B-pillar satellites are identical to those on other BMW models. It is important to make sure the part number is correct. The airbag indicator lamp will come on if the incorrect satellites are installed. 23 E70 Advanced Crash Safety Module Digital Data Transmission by Means of Current Interface The recorded acceleration values ofthe micromechanical acceleration sensors are con¬ verted in an ASIC (Application Specific Integrated Circuit) into digital signals. With the aid of a data telegram, the digital signals are transmitted uni-directionally to the crash safety module. The signals are transmitted via a current interface, which supplies the electronic circuitry with voltage. The electronic circuitry receives a voltage level of about. 5-10 mA via the current inter¬ face. The level rises at a step of 20 mA when a data telegram is transmitted so that only two lines per measurement channel are required. The transmitted data are evaluated in the crash safety module. Up-Front Sensors The up-front sensors in the front end on the left and right sides serve to detect a front-end crash.They deliverthe initial information on the progress and severity ofthe collision to the crash safety module. Each up-front sensor consists of an accelera¬ tion sensorfor recording the deceleration/acceleration, a signal conditioner and an ASIC for data transmission. The measured values are sent in the form of a data telegram to the crash safety module and are used in the calculation ofthe algorithm. The data are transmitted in the same way as the B-pillar satellites. Door Pressure Sensors The door pressure sensors in the front doors serve the purpose of verifying the plausibility ofthe acceleration signals from the B-pillar satellites and the crash safety module during side-on crash detection. The door pressure sensors are situated in the inner panels ofthe frontdoors and measure the increase in pres¬ sure within the door in the event of a side-on impact. 24 E70 Advanced Crash Safety Module In the event of a side-on impact with the door, the outer door panel is pressed inward, thus reducing the inner doorspace and increasing the pressure.This change in pressure is measured by the door pressure sensors. The door pressure sensor also includes an electronic module, which digitizes the pres¬ sure values and transmits them cyclically to the crash safety module. The data are trans¬ mitted in the same way as the B-pillar satellites. The pressure values are evaluated in the crash safety module. OC3 Mat US legislation stipulates that the use of a child restraint system conforming to NHTSA and holding a small child on the front passen¬ ger's seat must be detected automatically and the front passenger airbag disabled. The OC3 mat can detect an occupied child seat tested in accordance with the regulation (NHTSA FM VSS 208) on the basis ofthe pressure per unit area and disable the pas¬ senger airbag (front and side airbag). The passenger airbag OFF light comes on when a child restraint system tested in accordance with NHTSA and holding a small child was detected on the front passenger's seat. Emergency Call Button The emergency-call button is fitted as stan¬ dard in US vehicles, even if no telephone has been ordered. S eat- B elt B uc kle S witc hes The seat-belt buckle switches signal whether the seat belts are fastened or not. These switches transmit signals to the crash safety module and are used fortriggering the required restraint systems and forthe seat belt reminderfunction. The seat belt buckle switch is located in the seat belt buckles ofthe driver's and front passenger's seat. The seat-belt buckle switch is designed as a two-wire Hall-effect switch.The crash safety module powers the Hall switch via a current interface. The cur¬ rent intake ofthe switch varies depending on whetherthe seat belt is fastened or not. The seat belt buckle switch is permanently monitored as from "Terminal RON". 25 E70 Advanced Crash Safety Module Actuators The crash safety module is responsible for activating the following actuators: • Front airbag, 2-stage, driver's side • Front airbag, 2-stage, passengerside • Head airbag, left and right • Left and right side airbag integrated in the back rest of both front seats • Seat belt pretensioner, front, left and right • Adaptive seat belt force limiter, left and right • Safety battery terminal The following warning lamps are additionally activated: • Airbag indictor lamp • Seat belt indicator lamp • Passenger airbag OFF light 26 E70 Advanced Crash Safety Module Front Airbag, Driver In conjunction with the seat belt, the driver's front airbag is designed to reduce the risk of serious injury to the driver's head orthorax during a head-on collision. The front airbag for the driver's side is located in the hub cushion of the steering wheel. The driverfront airbag is equipped with a 2-stage inflator assembly. The two stages of the airbag are triggered with a time delay depending on the crash severity and use of seat belt. The two stages of the inflator assembly facilitate a restraint function adapted to the crash severity and consequently reduce additional stress on the occupants during the development phase. Index Explanation 1 Connection of firing pellet, first stage 2 Connection offiring pellet, second stage Front Airbag, Passenger Together with the seat belt, the task of the front airbag on the passenger's side is to reduce the risk of serious injury to the front passenger during a frontal crash. The 2-stage front airbag on the passenger's side is located underthe instrument panel. Deployment of the front passenger airbag breaks the instrument panel at defined points and opens a flap, which is connected to the instrument panel by means of a fabric strap. The passenger airbag opens in the direction of the windshield. The passenger airbag emerges in an upward direction and is supported on the windshield and on the instru¬ ment panel. 27 E70 Advanced Crash Safety Module Curtain Airbag The well-proven curtain airbag is used as the head protection system in connection with the ACSM on the E70. The curtain airbag extends from the A-pillarup to the C-pillarand covers the entire side section at head level. The curtain airbag inflates between the occupants and side win¬ dows or side trim panels. In connection with the side airbag in the front seat, it provides optimum protection forthe occupants in the event of side impact. The curtain airbag reduces the movement of the head and other extremities towards the outside during a side crash. This results in lower neck shearforces as well as bending moments in the cervical vertebrae. In addition, it also prevents direct head contact with the side structure ofthe obstacle. The inflator assembly (gas generator) mounted between the B-pillarand C-pillaris trig¬ gered in the event of a side crash. The gas flows out ofthe pressure vessel through the two gas lances into the curtain airbag. Simultaneously filling the curtain airbag at the front and rear ensures the air cushion is filled uniformly. The head airbag is brought into position because ofthe way the curtain airbag is mount¬ ed on the A-pillar and the C-pillar. The curtain airbag extends between the side window and side trim panel and the occupants. The closed system retains the structural strength and stability ofthe curtain airbag for several seconds 28 E70 Advanced Crash Safety Module Side Airbag For many years now, the side airbag has been used at BMW as an important integral part in occupants safety and protection systems. The task of the side airbags is to minimize the risk of injury to the driver/front passenger in the trunk/torso area in the event of a side impact. The side airbags mounted in the back rest of the front seats with the aim of achieving optimum interiorfunctionality and appealing design in the E70 while also satisfying the demanding safety requirements. The task of the side airbags is to minimize the risk of injury to the driver/front passenger in the pelvic and trunk/torso area in the event of a side impact. The side airbag is triggered in response to a sufficiently strong pulse from the side. The side airbag emerges through the tear seam in the backrest and inflates between the door and occupant. The air cushion between the door and occupant provides controlled damp¬ ing and therefore reduces load/strain on the occupant. Front Seat Belt Pretensioner The task of the pyrotechnic seat belt pretensioner is to minimize the seat belt slack in the pelvis and shoulder areas in the event of a crash, thus also preventing "submarining", i.e. slipping under a slack seat belt. The seat belt pretensioners are located on the driver's, front passenger's and left and right rear seats. The seat belt pretensioners are fired in the event of a front- or rear-end crash. In the E70 they are also activated in the event of an imminent rollover. Index Explanation 1 Before triggering 2 After triggering 29 E70 Advanced Crash Safety Module Adaptive Seat Belt Force Limiter The pyrotechnic seat belt force limiterforthe driver and front passenger is designed as seat belt retractor with adaptive force limitation. The force is changed overfrom a high level to a lower level with the aid of a gas generator. This must also be possible during a crash in orderto achieve gradual force reduction. The kinetic energy of the occupant is uniformly reduced overthe duration of the crash thanks to optimum matching with the airbag, thus achieving lower occupant stress values. Adaptive force limitation is achieved in that a second torsion shaft can be optionally coupled or de-coupled by the main torsion shaft, Index Explanation 1 Second torsion shaft 2 Gearwheel on second torsion shaft 3 Pyrotechnic actuator 4 Gearwheel on first torsion shaft 5 Seat belt reel When the two gear wheels are positively engaged, the two torsion shafts rotate as the result of the force applied by the belt. The torque of the two torsion shafts counteracts the belt force. Adaptive Seat Belt Force Limiter Positive The belt force is transmitted through the seat belt webbing to the belt reel. Engagement Index Explanation 1 Second torsion shaft 2 First torsion shaft 3 Seat belt reel 30 E70 Advanced Crash Safety Module Adaptive Seat Belt Force Limiter Non-Positive Engagement When the pyrotechnic actuator is triggered, the second torsion shaft shifts upward thus disengaging from the first gearwheel. Only the first torsion shaft is now subjected to the torque of the belt and therefore turns at a greater rate. Index Explanation 1 Second torsion shaft 2 First torsion shaft 3 Seat belt reel Safety Battery Terminal The safety battery terminal is triggered at different thresh olds when the crash safety module detects a front-end, side-on or rear end crash of sufficient severity. The connec¬ tion between battery and starter/ alternator cable is then separated by pyrotechnical teams. At the same time, the alternator is switched off by means of a crash telegram sent to the DM E. The safety battery terminal is located directly at the positive terminal of the battery. 31 E70 Advanced Crash Safety Module Service Information General Safety Regulations The safety information provided in the repair instructions must be complied with whether working on the safety system, particularly on the airbag units and the seat belt pretensioners. This requirement applies particularly to disassembly and assembly jobs. • Only qualified and specially trained personnel are permitted to perform testing and assembly jobs on the safety systems. • All work on components of the airbag system must be carried out with the negative terminal disconnected. • The specified waiting time must be allowed to elapse to discharge the capacitors (>30 s) • The battery must be completely disconnected when performing electric welding work on the vehicle. Crash Safety Module Crash entries In the event of a crash where one or more actuators are triggered, a crash entry is stored in a non-erasable memory. Afterthree crash entries, a non-erasable fault entry is stored in the fault memory with the instruction to replace the crash safety module. Fault entries The entry of a triggered restraint system in the fault memory does not mean that the restraint system was defective in the crash situation, rather it only means that the restraint system is not available for further triggering. B - pillar S atellite Visually, the B-pillar satellites look like those on other BMW models. However,they trans¬ mit different data protocols. It is important to make sure the part number is correct. The airbag indicator lamp will come on if the incorrect satellites are installed. 32 E70 Advanced Crash Safety Module