fuel BMW 7 SERIES 1999 E38 MRSIII Multiple Restraint System Manual

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MULTIPLE RESTRAINT SYSTEM (MRS III)
INTRODUCTION
The X5 is equipped with the Multiple Restraint System (MRS III) which 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 s\
everity 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 \
3/99 p roduction
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.
• The inert gas is a mixtu re of hyd rogen (13.5%) and oxygen (8 6.5%).

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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.