Table of Contents PASSIVE SAFETY SYSTEMS Subject Page MRS II .3 Head Protection System.4 Triggering Logic.5 Battery Safety Terminal.6 Diagnosis and Service Procedures.8 MRS III .9 Components MRS III Control Module.11 Satellite Sensors.12 Driver’s Front Airbag.13 Passenger’s Front Airbag.14 Side Airbags.15 Head Protection System.16 Battery Safety Terminal.17 Seat Belt Tensioners.18 Seat Occupancy Sensor (SBE).18 MRS III Operation.19 Triggering Thresholds (two stage airbags).20 MRS III I.P.0.21 Triggering Thresholds.22 Workshop Hints.23 RPS .24 Purpose of the System.25 Components Roll Over Bar Cassettes.26 Roll Over Sensor..28 Diagnosis and Testing.31 Review Questions .32 Initial Print Date: 7/98 Revision Date: 12/03/00 Multiple Restraint System II (MRS) Model: E46/4 Production Date: 6/98 to 9/99 Objectives After completing this module you should be able to: • Identify the components used in the MRS II system. • Describe the operation of the ITS. • Understand the triggering logic used by MRS II. • Describe the operation and repair procedure for the BST. 2 Passive Safety Systems MULTI-RESTRAINT SYSTEM (MRS II) The MRS II passive safety system is standard equipment on all 1999 M.Y. E46 models. The system is a carry over from the MRS II system introduced on 98 Model Year E38/E39s. The MRS II system for the E46 consists of the following: • MRS II Control Module • Driver and passenger's front air bags • Driver and passenger's side air bags (thorax) • Driver and passenger's Head Protection System (ITS) • Front pyrotechnic seat belt tensioners • Rear passenger's side air bags (thorax) • Battery Safety Terminal (BST) • Hall effect seat belt switches • Front passenger's seat sensor (SBE) • Driver and passenger's side impact sensors DRIVER'S SEATBELT SWITCH + — -c> ft— PASS. SEATBELT SWITCH +- A •— PASSENGER SEAT OCCUPIED (YES/NO) n n n DRIVER'S SIDE IMPACT SENSOR nru^ PASS. SIDE IMPACT SENSOR nnTL ITS ACTIVATION AIRBAG DEPLOYMENT BELT TENSIONERS | OPTIONAL REAR SEAT SIDE AIRBAGS ^CRASH SIGNAL BST 3 Passive Safety Systems HEAD PROTECTION SYSTEM (ITS) The ITS consists of a hermetically sealed rubber tube that is encapsulated by a cross woven tubular nylon material. Each ITS is mounted from the "A" pillars to the roof panel just behind the "B" pillars by a nylon strap and mounting bolt. When deployed, the inflation charge causes the diameter of the ITS to expand and its length to shorten. As the length shortens, it is forced out of its stowed position of the roof lining and it extends over the glass to protect the driver or passenger's head. The ITS remains inflated for approximately seven to eight seconds to extend the protection time should the vehicle encounter additional side impacts during the crash. LENGTH = X ITS TUBE 4 Passive Safety Systems MRS II TRIGGERING LOGIC FRONTAL IMPACT: - Deployment of the front air bags and/or seat belt tensioners is dependent on the severity of the impact as detected by the internally mounted crash sen¬ sor of the MRS II control module. Additionally, the MRS II looks at the input from the SBE for deployment of the passenger's front air bag. Deployment of the seat belt tensioners is also dependent on the presence of a signal from the seat belt switches. SIDE IMPACT: - Deployment of the Side impact air bags and head protection (tubular structures) is dependent on the severity of the impact as detected by the MRS II control module and the side impact sensors. Generally only the impacted side will be triggered. The tubular ITS structures and rear side air bags will always be deployed with the front and side air bags. 2 KLR -C- ELECTRONIC ACCELERATION SENSOR SIGNAL GENERATOR DRIVER'S SIDE IMPACT SENSOR (-- 2 KLR -C- ELECTRONIC ACCELERATION SENSOR PASSENGER'S SIDE IMPACT SENSOR SIGNAL GENERATOR $ t FRONT CC o o 2 TRIGGER LOGIC MRS II CONTROL MODULE EXAMPLE: INTERNAL ELECTRONIC ACCELERATION SENSOR DETECTS IMPACT ON PASSENGER SIDE OF VEHICLE PULSE WIDTH REDUCED; INDICATIVE OF SIDE IMPACT DRIVER'S SIDE PASSENGER'S SIDE 5 Passive Safety Systems BATTERY SAFETY TERMINAL (BST) The BST is an encapsulated pyrotechnic device. It is designed to prevent short circuits from occurring in the battery power supply to the engine compartment during impacts or colli¬ sions. The ignitor capsule of the BST will be triggered, by the MRS II control module, with any front air bag activation. The BST may be triggered with a side or rear impact, depending on the severity of the col¬ lision as detected by the MRS II control module. TO POWER DISTRIBUTION CENTERS X TO B+, STARTER y\ AND GENERATOR INTEGRAL IGNITOR CAPSULE TAPERED B+ CABLE CONTACT POINT SPRING TABS BST ENCAPSULATED HOUSING 6 Passive Safety Systems BST ACTIVATION Once activated, The ignitor generates a gas charge which is directed down the internal discharge tube. This causes the tapered end of the B+ cable contact to dislodge from its seated position which immediately opens the circuit. The force of the charge continues to push the cable contact away from its seated contact. The spring tabs of the housing are compressed as the contact pushes to the end of its travel. 7 Passive Safety Systems MRS II DIAGNOSIS AND SERVICES PROCEDURES Diagnosis is possible with the MODIC or DIS tester, the DIS allows symptom troubleshooting, test mod¬ ules, and ETM coverage of the ITS and BST. Installation of a replacement MRS II Control Module requires ZCS coding also using the DIS or MoDiC. Typical with any airbag, it is to be replaced as a unit after deployment. This is the same for ITS assemblies and the BST. Follow the precautionary measures outlined in the repair manual section of TIS, and always disconnect the battery prior to any repairs. All airbag units including the ITS assemblies are part number specific by model. Always use the EPC to verify the correct part number for any system part prior to ordering. Once a BST has been activated the metal crimp of the B+ wire is pushed out of the BST housing and exposed. This provides a quick visual check of it’s circuit status. A BST replacement splice kit is available from parts, this BMP i 15 HA fhnliB and iralallr^g^nplKln-D lull nr riphl TtStaad -urhig Imroei I !■—-■ --— El . — activated bst eliminates replacing the entire B+ (crimp exposed) cable. The splice kit comes complete with instructions and wire cutting/striping mea- ' surements. Follow instructions completely to bst replacement splice kit prevent future voltage drop problems in this cru- (crimp not exposed) cial circuit. 8 Passive Safety Systems Multiple Restraint System III (MRS) Model: E46/2, E46/4, E46/3, E46 Convertible Production Date: E46/4 from 9/99, all others from start of production. Objectives After completing this module you should be able to: • Understand the difference in airbag triggering logic over the previous MRS system. • Describe how the two different ignition stages of the front airbags are triggered to create three different inflation speeds. • Explain the method used by the MRS for shutting off the fuel pump 9 Passive Safety Systems MULTIPLE RESTRAINT SYSTEM (MRS III) INTRODUCTION The Multiple Restraint System (MRS III) employs the use of “SMART” technology. Smart technology refers to the control module’s programming which allows for the deployment of the airbags, in stages, depending on the severity of the impact. Two stage airbags are used for both the driver and front passenger which allows for a softer cushioning effect when the bags are triggered at lighter impacts. The MRS III system is installed in E38/E39 and E46 Sedan vehicles as of 9/99 production and in E46 Coupes as of 6/99 production. MRS III control modules are manufactured by either Bosch or Temic. While the functional operation of both modules are the same. The control modules are not interchangeable from a replacement standpoint. Always refer to the EPC parts system to ensure that the proper module is installed in the vehicle. In addition to the use of two stage airbags for the driver and passenger, the following fea¬ tures are also included in the MRS III system: • The MRS III control module is linked to the K-Bus for coding and diagnosis. • The MRS III includes a fuel pump cut off feature in the event of an airbag deployment. • Inert gas generators are now used for all air bags and seat belt tensioners. (This method is referred to as Cold Gas Inflation.) • The inert gas is a mixture of compressed Hydrogen (13.5%) and Oxygen (68.5%). 10 Passive Safety Systems COMPONENTS MRS III CONTROL MODULE The control module is mounted in the center console area on the driveshaft tunnel below the emergency brake handle. The control module contains the processing electronics (Smart Technology) for triggering of all air bags and pyrotechnic devices installed in the vehicle. Two electronic deceleration sen¬ sors are installed in the module for crash or impact detection. 11 Passive Safety Systems SATELLITE SENSORS The satellite sensors are mounted below the driver’s and passenger’s front seats on the seat frame. The function of the sensors is to detect the severity of side impacts and signal the MRS III control module, through a pulse modulated signal, in the event of a crash. The control module uses this input signal along with its internal impact sensor signal to deter¬ mine the deployment of the side/head airbags. As with the control modules, the satellite sensors are manufacturer specific. The Temic sensors have a three wire connector which will not interchange with the Bosch sensors. Only two of the wires are used for the satellite sensor’s operation. The signal for deploy¬ ment of the bags is carried over the power wire of the sensor. DRIVER’S SIDE IMPACT SENSOR PASSENGER’S SIDE IMPACT SENSOR ruin ruin CRASH SIGNAL OUTPUT GENERAL MODULE 12 Passive Safety Systems DRIVER’S FRONT AIRBAG The driver’s front airbag is a two stage bag similar to the passenger’s front side bag. The complete assembly is mounted beneath the cover in the center of the steering wheel as with previous airbags. The assembly now contains the inert gas generator chamber and two ignition stages (ignitors). The airbag consists of: • Accumulator/gas generator • Two ignition capsules • Propellant gas - 13.5% Hydrogen/86.5% Oxygen 13 Passive Safety Systems PASSENGER’S FRONT AIRBAG The passenger’s front airbag is similar to the unit installed on E38/E39 vehicles as of 9/98 production. The passenger’s airbag consists of: • Pressure accumulator/gas generator • Two ignition capsules - for two stage activation • Propellant gas of - 13.5% Hydrogen/86.5% Oxygen PRESSURE ACCUMULATOR 14 Passive Safety Systems SIDE AIRBAGS FRONT/REAR (THORAX) The side airbags continue to be mounted behind the door panels on the front and rear doors. Deployment of the side airbags is dependent on the triggering thresholds pro¬ grammed in the MRS III control module, based on the inputs from the satellite sensors and internal crash sensor. The side airbags use the same inflation method as the driver’s and passenger’s front bags. 15 Passive Safety Systems HEAD PROTECTION AIRBAG (ITS: Inflatable Tubular Structure) The head protection airbags are similar to the ITS bags used on the MRS II system. They continue to be mounted from the “A” pillar up along the headliner and are anchored behind the “B” pillar. The ITS bags of the MRS III system are also the cold gas inflation type. The head airbags are always triggered with the side (Thorax) bags. 16 Passive Safety Systems BATTERY SAFETY TERMINAL (BST) As with previous systems, the BST is used to disconnect the battery’s “B+” connection to the engine compartment in the event of an airbag deployment. The safety measure helps prevents the possibility of a short circuit causing a fire. TO POWER DISTRIBUTION CENTERS X TO B+, STARTER TJ AND GENERATOR INTEGRAL IGNITOR CAPSULE TAPERED B+ CABLE CONTACT POINT SPRING TABS BST ENCAPSULATED HOUSING 17 Passive Safety Systems SEAT BELT TENSIONERS The seat belt tensioners are a new design and also make use of the inert gas for trig¬ gering. The MRS III control module will deploy the seat belt tensioners based on the programmed parameters during impact. SEAT OCCUPANCY SENSOR (SBE) The SBE continues to be used as an input to the MRS III control module for detection of a front seat passenger. The module uses the input to determine seat belt tensioner and/or front airbag deployment. 18 Passive Safety Systems MRS III OPERATION As with previous systems, the triggering thresholds are programmed in the MRS III control module. These thresholds are determined by BMW through crash and vehicle testing dur¬ ing the design and development of the vehicle. These thresholds will vary depending on the vehicle size and design. There are several different thresholds for airbag and safety restraint deployment: • Belt pre-tensioner threshold for activation of the seat belt tensioners. • Airbag threshold #1 - the first level of activation for the two stage front airbags, always deployed first when the front triggering threshold is reached. • Airbag threshold #2 - the second level of the two stage front airbags, can be deployed simultaneously or after a time delay, depending on the severity of the impact. • Rear crash threshold - for activation of the seatbelt tensioners with a rear impact. • Battery safety terminal threshold - for activation of the BST with airbag deployment. • Side airbag/ITS threshold - for deployment of the side and thorax airbags. 19 Passive Safety Systems MRS III OPERATION TRIGGERING THRESHOLDS - TWO STAGE AIRBAGS The programming of the MRS III includes four triggering thresholds for the two stage front airbags. The triggering of the front airbags is also dependent on whether the seat belts are connected and if the front passenger seat is occupied. The triggering thresholds for the two stage airbags are as follows: THRESHOLD NO-SEATBELT BELTED 1 Ignition Stage 1 No Activation 2 Ignition Stage 1 & 2 with Time Delay Ignition Stage 1 3 Ignition Stage 1 & 2 with Time Delay Ignition Stage 1 & 2 with Time Delay 4 Ignition Stage 1 & 2 Simultaneously Ignition Stage 1 & 2 Simultaneously If the signal from the SBE is defective on triggering, the MRS III will deploy as if the seat is occupied. If the signal from the seat belt contacts are defective, the MRS III will deploy as if the belts were not buckled. 20 Passive Safety Systems MRS III l-P-0 DRIVER'S SEATBELT SWITCH + - A PASS. SEATBELT SWITCH r +- a PASSENGER SEAT OCCUPIED (YES/NO) DRIVER'S SIDE IMPACT SENSOR rum. PASS. SIDE IMPACT SENSOR MRS III