belt tensioner BMW 528i 2000 E39 User Guide

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400-8
Body-General
Airbags
Front airbags, s~de a~rbags, pyrotechnic seat belt tensioners
and the Battery Safety Terminal (BST) are integrated into the
Supplemental Restraint System (SRS) and its variants.
NOTE-
The BMW SRS system is called Multiple Restra~nt System
(MRS). Over the years,
E39 cars were equipped with MRS,
MRS
11, MRS 111. Each version offers varied features and im-
provements over the previous system.
< As many as 8 airbags may be installed in E39 cars, depend-
ing on model and MRS version.
The front
airbags operate without sodium azide propellant,
widely considered an irritant when an
airbag is deployed.
Starting with
1999 models. "smart"front passenger and driver
airbags were installed. These are of the dual-threshold, dual
stage design, including a
sensorto help prevent the unneces-
sary deployment of the passenger side
airbag if the seat is un-
occupied.
MRS control Depend~ng on options chosen, one airbag may be installed in module each door of the sedan and Sport Wagon models, protecting
passengers against
s~de impacts.
Head Protection System (ITS)
airbags strelch diagonally
across the tops of the front doors.
Airbag deployment automatically triggers fuel shutoff, turns
on the hazard and interior lights, and unlocks the doors.
- -
WARNING -
Airbags are inflated by an explosive device. Handled im-
properly or without adequate safeguards,
airbag units can
be very dangerous. Special precautions must be observed
prior to any worlc at or near any of the airbags. See
721 Air-
bag System (SRS).
Always disconnect the battery and cover the negative
(-) battery terminal with an insulator before starting di-
agnostic, troubleshooting or service work on cars fitted
with SRS, and before doing any welding on the
car.

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l Seats
Seat repair and component replacement is possible once the
seat has been removed from the vehicle.
Before servicing front seats read safety regulations on han-
dling
airbag modules and pyrotechnic seatbelt tensioners.
See
720 Seat belts and 721 Airbag system (SRS).
WARNING-
. The front seats are equipped with pyrotechnic seat belt
tensioners. These tensioners are powerful devices and
should be handled with exfreme care. Incorrect handling
can trigger off the tensioner and cause injury.
BMW recommends that all repair or replacement
worlc
on pyrotechnic devices must be carried out by a quali-
fied
BMW technician.
Be sure to disconnect the battery and wait
5 seconds
before attempting to work on pyrotechnic devices.
During body straightening and welding with an electric
arc welder, always disconnect the battery and the con-
nection to the pyrotechnic gas generators.
Seat switch and memory module, removing
and installing
- Remove front seat. See Front seats, removing and install-
ing.
- Carefully pull seat adjusting ltnobs straight out to remove.
Remove screw fastener
(A) and trim clips (B), turn side panel
downward to remove.
Disconnect electrical harness connector
(arrow).

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........... General ........................... .72 0.2 Rear Seat Belt Assembly 720-8
......... Troubleshooting ..................... .72 0.2 Rear seat belt assembly (sedan) 720-8
................ Rear seat belts (sedan) 720-9
... .......... Front Seat Assembly '720-4 Rear seat belt assembly (Sport Wagon) 720-9
Front seat belt tensioner,
......... Rear seat belts (Sport Wagon) 720-10
removing and installing ................ .72 0.4
Front seat belt assembly
.............. .72 0.6
Front seat belt reel. removing and
installing (sedan and Sport Wagon models)
.72 0.6

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I Seat Belts
This section covers repairs to the following seat belts sys-
tems. See the table below.
IMultIple Restraint Systems I
Years
311 996 - 811 997
Multiple Restraint System electronics integrate seat belt op-
erations and
airbag deployment. Airbag repair information is
covered
in 721 Airbag System (SRS).
Troubleshooting
The seat belt reel should lock when driving quicltly through
curves,
during severe braking or in case of a collision. The au-
tomatic reel does not require any servicing and should never
be opened.
- In case of an accident, follow the seat belt troubleshooting
procedures presented
in the table below.
Troubleshooting procedures
Belt creased, unraveled, pinched, cut or
melted. Belt buckle or belt loclt plastic casing Repairs
Replace complete automatic
seat belt.
Also
checlt and replace, if necessary, seat
Problem
Damage to seat
belt.
worn, damaged or missing.
Seat belt bucltle is not ejected with spring
pressure when red button on seat belt loclt is
>--- I I
Automatic belt soueaks when fastened or I~xcessive friction in belt guides. I Replace reel assembly.
Probable
cause
Accident in which bumper impact absorbers
were permanently deformed.
Seat belts aged or worn.
pressed.
Seat belt automatic reel does not lock when
pulled out suddenly.
Seat belt automatic reel jams when pulled
out.
Seat belt does not retract automatically
(see note below).
Automatic reel loose. Return sorino broken inside reel. belt mounting on car body and
seat belt
mounting on seat runner.
Replace complete automatic seat belt.
Seat belt
loclt mechanism worn or
damaged.
Tighten reel mounting bolt Replace reel assembly.
Replace seat belt lock.
Automatic reel defective.
Automatic reel loose. Return spring
broken inside reel.
Automatic reel loose.
Return spring brolten inside reel. Replace reel
assembly.
Tighten reel mounting
bolt.
Replace reel assembly.
Tighten reel mounting bolt. Replace reel assembly.
~ ~-~~ , - I'
Replace complete automatic seat belt.
Also check retaining bracket of belt
Seat belt
pyrotechnic tensioner triggered. Accident triggered pyrotechnic deployment.

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- -
Seat Belts
Front seat belt tensioner, removing and
installing
- Disconnect battery negative (-) cable in trunk.
The
front seat belt loclts are equipped with pyrotechnic (ex-
plosive charge) automatic tensioners. These tensioners are
designed to automatically retract and tension the seat belt by
55 mm (approximately 2 inches) in the event of an accident.
CAUTION-
Prior to disconnecting the battery, read the battery discon-
nection cautions given in
001 General Warnings and Cau-
tions.
WARNING-
Pyrotechnic seat belt tensioners are powerful devices and
should be handled with extreme care. Incorrect handling
can trigger the tensioner and cause injury
BMW recommends that all repair or replacement work
on pyrotechnic devices must be carried out by a quali-
fied BMW technician.
Be sure to disconnect the battery and wait
5 seconds
before attempting to work on pyrotechnic devices.
Pyrotechnic devices cannot be repaired. Always re-
place them.
Never treat pyrotechnic components with cleaning
agents or grease.
- Do not expose pyrotechnic components to tempera-
tures above
75% (167°F).
Pyrotechnic components can only be tested electrically
when installedusing the
BMWService Tester (DISplus,
GTI, or MoDiC).
Do not fire a pyrotechnic gas generatorprior to dispos-
al. It must be fired by a special disposal company or
shipped
back to BMW in the packaging of the new com-
ponent.
During body straightening and welding with an electric
arc welder, always disconnect the battery and the con-
nection to the pyrotechnic gas generators.
- Remove front seat as described in 520 Seats.
-

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Seat ~eltsl
< Remove tensioner cover:
Cut wire ties (A).
Release wiring harness from tensioner cover clip (B).
- Release tensioner cover locks (C) and slide cover down to
remove.
- When reinstalling:
Replace wire ties to relieve tension on pyrotechnic belt
ten-
sioner harness connector.
Tightening torques . -
Front seat to floor (M10) 42 Nm (31 it-lb)
Seat belt to seat 48 Nm (35 It-lb)
Tensioner mounting bracitet
to seat rail 24 Nm (18 it-lb)
Tensioner to mounting bracket 48 Nm (35 it-lb)

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I Seat Belts
a
Front seat belt assembly
1. Seat belt buckle
2. Seat belt stop button
3. Seat belt
4. Seat belt height adjuster
5.
6-pillar cross brace
6. Seat belt reel mounting bolt
7. Seat belt anchor mounting bolt
8. Seat belt lock with pyrotechnic
tensioner
9. Tensioner mounting bolt
Front seat belt reel, removing and installing
(sedan and Sport Wagon models)
- Detach battery negative (-) cable in trunk.
~~-~
Prior to disconnecting the battery, read the battery discon-
nection cautions given in
001 General Warnings and Cau-
l tions. I
- Remove front seat as described in 520 Seats
4 Gently pry up front and rear plastic door sill protector strips
to remove.

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721 -2
l~irba~ System (SRS)
This repair group covers airbag components and replace-
ment.
Airbag system repairand fault diagnosis is not covered.
Diagnostics, component testing, and
airbag system repair
should be carried out by trained BMW service technicians.
Individual
airbag system components can only be tested elec-
tronically when installed in the car. BMW service testers
DIS
or MoDiC or equivalent must be used for diagnostic work.
WARNING-
Special test equipment is required to retrieve airbag fault
codes, diagnose system faults, and
reseffturn off the air-
bag indicator light. The indicator light will remain on until
any problem has been corrected and the fault memory has
been cleared.
Airbags are part of the BMW Multiple Restraint System
(MRS). Three versions of MRS are available in E39 models.
Multiple Restraint Systems
MRS and MRS II include the following restraint components:
311 996-811 997
911
997-311 999
311 999-2002
Driver and passenger front
airbags (MRSIMRS II)
MRS
MRS
II
MRS Ill
Passenger front two-stage airbag (cars manufactured
from
911998).
The seat occupancy sensor (SBE) is used for detection of
a passenger in the right front seat. MRS uses the SBE in-
put to determine seat belt tensioner
and/or front airbag de-
ployment thresholds.
Side impact
airbag for driver and front passenger
(MRSIMRS II)
Leftlright side impact crash sensors (MRSIMRS 11)
Side impact airbag for rear passenger (MRS II) (optional)
Head Protection System (HPS) for driver and front passen-
ger (MRS
II)
Battery Safety Terminal - BST (MRS II)
Hall Sensor seat belt switches (MRS II)
Front pyrotechnic seat belt tensioners
Fuel pump cut off message

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I Airbag System (SRS)
Two-stage airbag (MRS Ill)
Beginning with 2000 model year (911 999 production) the front
airbags were changed to a two-stage style airbag. This en-
sures that the force of
airbag inflation is not greater than nec-
essary to provide
protection. The airbags are designed to
Drovide "soit" de~lovment if the acceleration sensor detects a
iow-speed impact, and "hard deployment in higher speed im-
pacts.
NOTE-
A two-stage passenger airbag was used on cars built be-
tween
9/1998 and 3/1999. This pre-smart technology airbag
used two ignition stages. Stage one is designed to ignite first
during an impact. Stage two ignites after a timed period, as
programmed in the MRS
I1 control module.
Airbag indicator light
The MRS control module detects and stores system status
The
airbag indicator light in the instrument cluster displays
the status of the
airbag system when the ignition key is in "ac-
cessory" or
ON positions.
System normal: lndicator light comes on briefly, then goes
out.
- System malfunction: lndicator light fails to come on.
System malfunction: lndicator light comes on briefly, goes
out and lights up again.
The
airbag indicator light also comes on if the seat belt pyro-
technic tensioners have been triggered.

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721-6
I Airbag System (SRS)
MRS
The MRS control module contains the electronic crash sensor
for frontal impact. Sensors mounted on the driver and
pas-
sengerfloor are used for side impacts. The MRS control mod-
ule
is located between the front seat under the center
console.
MRS airbag system
diagram
1. Driver's side airbag
2. Passenger's side airbag
3. Right side impact sensor
4. Seat occupancy sensor pad
5. Right side impact airbag
6. SBE control module (analog to
digital converter)
7. Passenger pyrotechnic seat belt
tensioner and seat belt
mi-
croswitch (Hall sensor MRS Ill)
8. MRS control module
9. Driver pyrotechnic seat belt ten-
sioner and seat belt microswitch
(Hall sensor MRS
Ill)
10. Left side impact airbag
11. Left side impact sensor