Part I

Multiple Restraint System (MRS)

Multiple restraint system 6
The multiple restraint system 6 (MRS) is a continuous enhancement of the multiple restraint systems in MINI vehicles.
The MRS has the following tasks:
- Detecting an accident situation that is critical for the occupants
- Activating the necessary restraint systems (selectively depending on the severity of the accident and accident type)

Brief description of components
The following components are described for the multiple restraint system (see also national version):

MRS control unit
All inflator assemblies and sensors are connected directly to the MRS control unit.
The MRS control unit evaluates the data from the sensors.
In the event of a collision, the MRS control unit decides whether seatbelt tensioner and airbag triggering is required and which airbags have to be triggered.
Two acceleration sensors are fitted in the MRS control unit.
The longitudinal acceleration sensor detects a frontal or rear-end collision.
The transverse acceleration sensor detects a side-on collision.
An ignition capacitor is fitted in the MRS control unit. If the power supply is interrupted in a collision, the ignition capacitor serves as an energy reserve for the MRS control unit.

Front door airbag sensor on driver's side and front door airbag sensor on passenger's side
The 2 airbag sensors are pressure sensors. The airbag sensors are fitted in each of the inner door panels.
The airbag sensor consists of the following components:
- Pressure sensor for detection of a side-on crash
- Electronic module for signal processing and for data interchange
if the door outer skin is pressed inwards in a side-on collision, the door interior is reduced in size. This increases the pressure in the door interior. This increase in pressure is measured by the pressure sensor. The measured pressure values are digitized in the electronic module. The electronic module sends a message to the MRS control unit (cyclical message transfer). The message is evaluated in the MRS control unit.

Airbag sensor in the B-pillar driver's side and passenger's side

R55
One B-pillar airbag sensor is installed on the left-hand side of the vehicle in the B-pillar. The other B-pillar airbag sensor is installed on the right-hand side of the vehicle in the clubdoor.

R56
One airbag sensor each is fitted in the left-hand and right-hand B-pillar

Each of the 2 airbag sensors contain a transverse acceleration sensor and a longitudinal acceleration sensor.
The longitudinal acceleration sensor detects a frontal or rear-end collision.
The transverse acceleration sensor detects a side-on collision.

Belt buckle switch
The belt buckle switches indicate whether the seat belts have been fastened or not. The belt buckle switches are supplied with voltage by the MRS control unit. The current consumption of the switch is the signal for the switch position (seat belt fastened or not fastened). The belt buckle switches are monitored permanently as of terminal R On.







- Belt buckle switch for driver belt and passenger belt
The signal of the belt buckle switch decides whether the seatbelt tensioner is activated if required or not.
If the front passenger seat is recognized as being occupied without the seat belt buckle switch sending a signal, a fasten belt warning will be emitted.
Triggering of the seatbelt tensioner on the passenger's side depends on the status signal of the belt buckle switch (seat belt fastened or nor fastened). If the seat belt is inserted in the belt buckle switch, the seatbelt tensioner is also triggered (EURO version: only with frontal / rear-end collision; see also 'National version').

Passenger-seat occupancy detector
The passenger seat occupation detection detects whether the seat is occupied or not. The seat occupancy mat consists of conductors and pressure sensors. The conductor tracks are connected to the electronic evaluation unit.







When a weight is placed on the seat, resistance in the seat-occupancy mat changes. The seat occupancy electronics evaluate this change in resistance ("seat occupied" or "seat unoccupied" status).
The seat is recognized as being not occupied up to a weight of approx. 12 kg. The seat occupancy detector function, however, also depends on the type of seat.
For example: The material tension in a leather seat or a taut sports seat is already interpreted as pressure on the sensors. In such cases, a weight below 12 kg can trigger the "seat occupied" condition.
The signal is sent across a direct line to the MRS control unit. The signal is only required for the seat belt warning. For example, if the front passenger seat is recognized as being occupied without the seat belt buckle switch sending a signal, a fasten belt warning will be emitted.

Switch for passenger's airbag deactivation (EURO version)
In the switch position "OFF", the following airbags on the passenger's side are not inflated: Passenger's airbag and side airbag.
The indicator lamp for passenger airbag deactivation (passenger airbag off lamp) lights up.







For vehicles without a switch for passenger's airbag deactivation, there is a retrofit kit (optional extra 5DA "Passenger's airbag deactivation").
The switch is operated using the key integrated in the remote control.

CAS: Car Access System
The CAS control unit delivers input signals with regard to terminal voltage (e.g. terminal R On). The MRS control unit is supplied with voltage by the CAS control unit (as of terminal R).

DME or DDE: Digital Engine Electronics and/or Digital Diesel Electronics
When an airbag triggers, the DME or DDE switches off the electric fuel pump. The DME or DDE receives a message from the MRS control unit.

JBE: Junction Box Electronics
The JBE handles activation of the central-locking drives. In the event of an accident with the corresponding severity, the central-locking system is unlocked.

FRM: Footwell module
The footwell module controls the interior lighting and exterior lighting. In the event of an accident with the corresponding severity, the interior lights and hazard warning lights switch on automatically.

KOMBI: Instrument cluster
The instrument cluster shows the visual seat belt warning and issues an acoustic seat belt warning.
The MRS control unit activates the seat belt warning by means of a Check Control message.
The instrument cluster receives the status as of terminal R On from the MRS control unit. With the corresponding status, a visual and acoustic seat belt warning is issued as of terminal 15 On.
The instrument cluster also contains the airbag warning lamp.
The instrument cluster is connected via the K-CAN with the MRS control unit.

Firing circuits for the airbags
With maximum equipment, the safety system consists of the following firing circuits (see also national version):
- Driver airbag (stage 1)
- Front passenger airbag (stage 1)
- Driver airbag (stage 2)
- Front passenger airbag (stage 2)
- Side airbag in the driver's seat
- Side airbag in the passenger's seat
- Head airbag, driver's side
- Head airbag, passenger's side
- Seatbelt tensioner, driver belt
- Seatbelt tensioner, passenger belt

Driver's and front passenger's airbag
The driver and passenger airbags reduce the risk of head injuries or injuries in the area of the occupants' chest in a frontal collision.
The driver's airbag is located under the impact pad of the steering wheel. The front passenger's airbag is built into the instrument panel above the glove compartment.

Side airbag
The side airbags reduce the risk of injuries to the occupants in the lap or torso area in the event of a side-on collision. The side airbag are fitted in the armrest side sections of the front seats.

Head airbag
The head airbag prevents direct contact of the head against the side structure or an obstacle entering the vehicle. The head airbag stretches continuously at head height from the A-pillar to the C-pillar.
After triggering, the shape and stability of the head airbag are maintained for a number of seconds. The head airbag deflates more slowly than the front and side airbags. This means that the head is protected for longer in the event of overturning.
Head airbags are fitted on the driver's side and passenger's side.

Seatbelt tensioners for driver belt and passenger belt
As a rule, the seat belt does not fully tighten around the body. The so-called "belt slack" of the seat belt ensures that the occupants can move comfortably to an adequate degree. In the event of a frontal or rear-end collision, the pyrotechnic seatbelt tensioner pulls the belt buckle a number of centimeters downwards (bear the national version in mind). This tightens the seat belt simultaneously in the lap and shoulder region of the occupants.

Airbag control lamp
The airbag warning lamp indicates the proper functioning of the multiple restraint system. The airbag warning lamp in the instrument cluster is activated by the MRS control unit via the K-CAN.

Seat belt warning lamp
The seat belt warning lamp is the visual seat belt warning. The visual seat belt warning tells the occupants to fasten their seat belts. The visual seat belt warning is started as of terminal 15 On. (Bear the national version in mind.)
The visual seat belt warning is displayed as follows:
- Seat belt warning lamp in the instrument cluster
- Check Control symbol in the LC display in the instrument cluster

Indicator lamp for passenger's airbag deactivation
If the indicator lamp for passenger airbag deactivation (passenger airbag off- lamp) lights up, the following airbags on the passenger's side are disabled: Passenger's airbag and side airbag.
The passenger airbag off lamp is continuously monitored via the MRS control unit. A fault in the power supply or a defective lamp is stored in the fault code memory of the MRS control unit. In this case, the airbag warning lamp is switched on.

Fuel pump
Depending on the severity of the accident, the flow of fuel is also interrupted. The DME or DDE switches the electric fuel pump off.

Belt tension limiters on seat belts
The seat belts are the primary restraint system for all occupants.
To minimize the force in the chest area of the front-seat occupants in the event of a severe frontal collision, the front seat belts are equipped as series standard with belt tension limiters. The belt tension limiters ensure that the seatbelt strap has a defined flexibility as of a certain force. The risk of injury due to belt forces exerted on the body is reduced.