1: Introduction

Multiple Restraint System 5
R50, R52, R53






Introduction
The multiple restraint system 5 (MRS) is a direct development of the multiple restraint system fitted to MINI vehicles.

The multiple restraint system 5 is only fitted to US-version MINI vehicles. [System overview ...] 2: System Overview

The MRS performs the following functions:
- Recognises accident situations that are critical for vehicle occupants
- Activates the necessary restraint systems in the event of an accident (selectively, depending on the severity and type of accident)

Brief Description Of Components

The following sensors detect the direction and severity of an impact:
- Acceleration sensors in the MRS control unit
There is a lateral acceleration sensor and a longitudinal acceleration sensor in the MRS control unit. The sensors are arranged at 90 degrees to each other.

- Airbag sensors on left-hand B-pillar and right-hand B-pillar
Each of the airbag sensors on the B-pillars contains a lateral-acceleration sensor and a longitudinal-acceleration sensor. The sensors are arranged at 90 degrees to each other. [more ...] 3: Airbag Sensors on Left-Hand B-Pillar and Right-Hand B-Pillar

- Front airbag sensors
The 2 front airbag sensors are longitudinal acceleration sensors. [more ...] 4: Front Airbag Sensors

- Airbag sensors on front left door and front right door
The 2 airbag sensors are pressure sensors. [more ...] 5: Airbag Sensors on Front Left Door and Front Right Door

The following components provide additional input signals for the multiple restraint system:
- Passenger seat occupancy detector
Statutory guidelines in the USA stipulate that the seat occupancy detector mat integrated into the front-passenger seat must be able to recognise a child seated in a rearward-facing child seat. Upon detection, the airbags on the passenger side are automatically deactivated (passenger airbag and side airbag). The indicator lamp for passenger airbag deactivation lights up.
The seat-occupancy detector evaluates the impression caused from a load on the seat.
If the multiple restraint system (MRS) triggers the airbags and the front-passenger seat is unoccupied, the front-passenger airbag and the side airbag on the front-passenger side will not be triggered.
The head-level airbag will still be triggered. [more ...] 6: Passenger Seat Occupancy Detector

- Seat-belt buckle switch for driver's seat and front-passenger seat
The MRS control unit uses the signals from the driver's seat-belt buckle switch and the front-passenger seat-belt buckle switch to detect whether or not the seat belts are fastened.
If the seat belt is fastened, the seat-belt tensioner will also be triggered (only in the event of frontal impact or a rear-end collision).

The following control units are involved in the function of the MRS:
- MRS control unit
All triggering circuits and sensors in the multiple restraint system (MRS) are connected directly to the MRS control unit.
The MRS control unit evaluates the data it receives from the sensors. In the event of a collision (head-on, rear-end or side impact), the MRS control unit will decide whether the seat-belt tensioners and airbags need to be triggered, and which airbags need to be triggered. [more ...] 7: MRS Control Unit

- DME: Digital engine electronics
Depending on accident severity, the electric fuel pump will be switched off by the DME.
Signal path: MRS control unit -> K-bus -> General module -> K-bus -> Instrument cluster -> PT-CAN -> DME -> Direct wire -> Fuel-pump relay -> Electric fuel pump

- Instrument cluster
The instrument cluster generates the optical and audible seat-belt warning.
When terminal R is ON, the instrument cluster receives the status message from the MRS control unit via the K-bus. Depending on the status, the optical and audible warning is triggered when terminal 15 is ON.

- GM: General module
The general module is connected to the MRS control unit via the K-bus.
The general module is the executing control unit for the central locking system. The general module also controls the interior and exterior lighting.
Depending on severity, the central locking is unlocked in the event of an accident. The interior lights and the hazard warning lights are automatically switched on.
Signal path: MRS control unit -> K-bus -> General module

The following components are activated by the MRS control unit:
- Multiple restraint system triggering circuits
With maximum equipment, the MRS (multiple restraint system) comprises 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 in driver's seat
- Side airbag in front-passenger seat
- Head-level airbag, left (optional)
- Head-level airbag, right (optional)
- Belt tensioner, front left
- Belt tensioner, front right
- Safety battery terminal
Driver and front-passenger airbag
The driver and front-passenger airbag reduce 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 compartment.
Side airbag
The side airbags are located in the side sections of the front-seat backrests.
The relocation into the backrest side section has the advantage that there are no longer airbags in the doors, allowing the engineers more freedom when designing the doors.
Both versions, airbags in doors and airbags in seats, satisfy the strict legal requirements with regard to occupant safety to the same degree.
Side airbags reduce the risk of injury to the pelvis and torso of the driver and front passenger's in the event of a side impact. [more ...] 8: Side Airbag
Head-level airbag
The head-level airbag is optional on the hardtop model only, it is not available on the R52 Convertible.
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.
To prevent the negative effect that this loose belt can have, the pyrotechnic seat-belt tensioner will pull the belt buckle down by several centimetres in the event of a frontal or rear-end collision. This pulls the seat belt tight into the occupant's shoulder and pelvis.
Safety battery terminal
Depending on the severity of the accident, the safety battery terminal disconnects the starter motor and the alternator from the battery. (only diesel vehicles and R53.)
This minimises the risk of short circuits in a serious accident. The trigger signal comes from the MRS control unit.

- Airbag warning lamp
The airbag warning lamp shows the operational capability of the multiple restraint system (MRS). The airbag indicator lamp in the instrument cluster is activated by the MRS control unit (via the K-bus).

After the ignition is switched on, the MRS performs a self test. During this time, the airbag indicator lamp will light up (approximately 3 to 5 seconds). When the system is ready for operation, the airbag indicator lamp goes out.
If the instrument cluster has not received a bus signal, the airbag indicator lamp will light up.
If, during the self test or while the vehicle is in motion, the MRS control unit detects an existing fault or one that has been stored, the airbag warning lamp remains on.

If the MRS detects a fault, the operational capability is partially maintained, subject to the following:
- If a fault is detected in an MRS circuit, 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 MRS remains fully operational.
If there is an internal fault in the MRS control unit or in the power supply, the entire system is deactivated. (airbag and seat belt warning lights come on)

- Seat-belt indicator lamp
The seat-belt indicator lamp is the visual seat-belt warning. The visual seat-belt warning instructs the front-seat occupants 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 indicator lamp in the instrument cluster (required by law)

- Indicator lamp for front-passenger airbag deactivation
After the ignition is switched on, the MRS performs a self test. In this time, the warning lamp for passenger-airbag deactivation lights up (approx. 3 to 5 seconds). The status of the airbags on the passenger side (passenger airbag and side airbag) is then displayed.
If the warning lamp for passenger-airbag deactivation ("Passenger Airbag OFF" lamp) is lit, the following airbags on the (occupied) passenger side have been deactivated: front-passenger airbag and side airbag.
The "Passenger Airbag OFF" lamp is constantly monitored by the MRS control unit. A fault in the power supply or a defective lamp is stored in the MRS control unit's fault memory. If this occurs, the airbag warning lamp is switched on.
"Passenger Airbag OFF" lamp installation location: R50/R53: roof console R52: cowl panel

- Electric fuel pump cutoff
Depending on accident severity, the fuel supply may also be cut off.
Signal path: MRS control unit -> K-bus -> General module -> K-bus -> Instrument cluster -> PT-CAN -> DME -> Fuel-pump relay -> Electric fuel pump

Mechanical components in the multiple restraint system (MRS):
- Belt force limiters on seat belts
The seat belts are the primary restraint system for all occupants. Each of the 4 seats is fitted with a lap and diagonal automatic belt.
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 slightly if the load exceeds a certain level. The risk of injury due to the belt force acting on the body is thus reduced.

- Knee protection
An additional impact protection is fitted in the area of the knees on the driver's and front-passenger side. This knee protection provides extensive support for the knees in the event of an accident. The knee protection reduces the load on the lower extremities, especially if the front occupants are not wearing their seat belts.
At the same time, a controlled forward movement of the upper body towards the relevant airbag (driver or passenger airbag) is initiated.

System functions
The following system functions of the multiple restraint system (MRS) are described:
- Triggering the multiple restraint system
- Visual and audible seat-belt warning

Triggering the multiple restraint 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 tensioner
- Front airbags
- Side airbags and head-level airbags
- Safety battery terminal
- Electric fuel pump

The following examples illustrate how the various restraint systems are triggered:
- Head-on collision
The belt tensioner and the front airbags are activated if frontal impact is sufficient to exceed the triggering thresholds in the MRS control unit.
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 MRS control unit.
If the seat-belt buckle switch is faulty, the MRS control unit 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 not occupied. The restraint systems are not 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 MRS control unit 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.

- Front diagonal impact
The airbags and belt tensioners are triggered depending on the rate of vehicle deceleration in a longitudinal or lateral direction.
If several triggering thresholds are exceeded, the corresponding restraint systems will be triggered for frontal collision and/or side impact (front airbag, side airbag, head-level airbag).
Depending on accident severity, the safety battery terminal is activated and the electric fuel pump switched off.

- Rear-end collision
The belt tensioners are activated if rear impact is sufficient to exceed the triggering threshold in the MRS control unit.
Depending on accident severity, the safety battery terminal is activated and the electric fuel pump switched off.

- Rear diagonal impact
The airbags (side airbags, head-level airbags) and belt tensioners are triggered depending on the rate of vehicle deceleration (or acceleration). If a number of triggering thresholds are exceeded, the appropriate restraint systems are activated.
Depending on accident severity, the safety battery terminal is activated and the electric fuel pump switched off.

- Rollover
The MRS control unit does not detect the vehicle rolling over.
The corresponding restraint systems are triggered: for example if the side impact causes the vehicle to roll over or if impact occurs while the vehicle is rolling over and the operating thresholds in the MRS control unit are exceeded.
Depending on accident severity, the safety battery terminal is activated and the electric fuel pump switched off.

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 passenger 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
- Driver's side only:
If the distance driven is less than 200 m, only the seat-belt warning lamp lights up. The vehicle may for example be driven out of a garage without triggering an acoustic seat-belt warning.

- Front seat belt not fastened and distance driven more than 200 m
The seat-belt warning lamps lights up. The acoustic seat-belt warning is activated for approximately 90 seconds.
Once the seat belt has been fastened, the seat-belt warning lamp goes out. The acoustic seat-belt warning is deactivated.
- Driver's side:
If the seat belt has not been fastened by the end of the acoustic seat-belt warning, the seat-belt warning lamp will stay on.
- Passenger side:
If the seat belt has not been fastened by the end of the acoustic seat-belt warning, the seat-belt warning lamp and the acoustic seat-belt warning are deactivated.

- Unfastening the front seat belt when the vehicle is in motion
- Driver's side:
The seat-belt warning lamps lights up immediately.
After approx. 15 seconds an acoustic seat-belt warning is activated for approx. 90 seconds.
Once the seat belt has been fastened, the seat-belt warning lamp goes out. The audible seat-belt warning is deactivated.
If the seat belt has not been fastened by the end of the acoustic seat-belt warning, the seat-belt warning lamp will stay on.

- Passenger side:
After approximately 15 seconds, the seat-belt warning lamp will light up and an audible seat-belt warning will be issued for approx. 90 seconds.
Once the seat belt has been fastened, the seat-belt warning lamp goes out. The audible seat-belt warning is deactivated.
If the seat belt has not been fastened by the end of the acoustic seat-belt warning, the seat-belt warning lamp and the acoustic seat-belt warning are deactivated.

Note:
Deactivating the acoustic seat-belt warning.
The acoustic seat-belt warning can be deactivated using encoding.
This does not affect a legally stipulated seat belt warning.

Notes for service staff
- General information: [more ...] General Information on Servicing the Multiple Restraint System
- Diagnosis: [more ...] Testing and Inspection
- Encoding/programming: ---
- Car & Key Memory: ---
Subject to change.