2000 BMW 3 SERIES SEDAN sensor

TABLE OF CONTENTS
Subject Page
Multiple Restraint System (MRS III) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
MRS III Control Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Satellite Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Driver’s Front Airbag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Passenger’s Front Airbag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Side Airbags Front/Rear (Thorax) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Head Airbag (ITS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Battery Safety Terminal (BST) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Seat Belt Tensioners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Seat Occupancy Sensor (SBE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
MRS III Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
MRS III I-P-O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Triggering Thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

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COMPONENTS
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 in
the X5 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 opera-
tion. The signal for deployment of the bags is car-
ried over the power wire of the sensor.

COMPONENTS
SIDE AIRBAGS FRONT/REAR (THORAX)
The side airbags continue to be mounted in the door panels on the front and rear doors.
Deployment of the side airbags is dependent on the triggering thresholds programmed in
the MRS III control module, based on the inputs from the satellite sensors and internal crash
sensor.
The side airbags use the same cold gas inflation method as the driver’s and passenger’s
front bags.
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COMPONENTS
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.

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TRIGGERING THRESHOLDS
SIDE AIRBAGS/ITS
The triggering thresholds for the side airbags/ITS is dependent on the signals from the
satellite sensors and the crash sensor in the MRS III control module. The triggering thresh-
olds are independent of the belt tensioners.
BELT TENSIONER
The triggering of the belt tensioners is dependent on the signal from the seat belt contact
and the severity of the impact as detected by the control module.
BATTERY SAFETY TERMINAL
The BST will deploy in a frontal impact at threshold 2 or greater. The threshold for BST acti-
vation with a side impact is programmed separately in the side deployment criteria. The
BST will also be deployed when the rear impact threshold is exceeded.
FUEL PUMP SHUT-DOWN
New to the MRS III system is the link via the K-Bus/CAN Bus to the Engine Control Module
for deactivation of the fuel pump. The MRS III will signal the DME over the K-Bus through
the instrument cluster and CAN Bus to shut off the fuel pump in the event that any crash
threshold is exceeded.

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DIAGNOSIS
Diagnosis and troubleshooting of the MRS III system is fault driven and can be accessed
using the DIS Tester or MoDiC. The control module performs a self test of the system every
time the ignition is switched on ( this includes the satellite sensors and seat occupancy sen-
sor). Any faults with the system will cause the warning lamp in the instrument cluster to
remain illuminated after the engine is started.
Installation of a new or replacement control module requires ZCS coding also using the DIS
or MoDiC.
When servicing or replacing any MRS III components, always follow precautionary mea-
sures outlined in the repair manual of TIS. this includes disconnecting the battery prior to
any repair or maintenance work being performed.
All airbag components are part number specific by model and require verification in the
EPC to ensure the correct component is being installed.