airbag BMW 525i 1997 E39 Service Manual

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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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Airbag System (SRS)~
Warnings
When servicing airbag equipped cars, the following precau-
tions must be
observed to prevent personal injury.
WARNING-
. If the airbag indicator light is on, there is a risk that the air-
bags will not be triggered in case of an accident Be sure
to have the system inspected and repaired immediately
Airbag(s) are inflated by an explosive device. Handled
improperly or witliout adequate safeguards, the system
can be very dangerous. Special precautions must be
observed prior to any work at or near the airbags.
0 The airbag is a vehicle safety system. Serious injury
may result if system service is attempted by persons
unfamiliar with the BMW
MRS and its approved service
procedures. BMW advises that all inspection and ser-
vice be performed by an authorized BMW dealer.
Always disconnect the battery and cover the negative
(-) battery terminal with an insulator before starting di-
agnostic, troubleshooting or service
work not associat-
ed
with the airbags, and before doing any welding on
the car.
0 After disconnecting the battery, wait 5 seconds before
beginning work on
airbag components.
* If an airbag has been activated due to an accident,
BMW specifies that
airbag components be replaced.
For more information on post-collision
airbag service,
see an authorized BMW dealer.
Do not fire an
airbag unit prior to disposal. It must be
fired by a special disposal company or shipped back to
BMW in the packaging of the new components.
When removing a fired
airbag unit, avoid contact with
the
skin; weargloves. In case ofskin contact, wash with
water.
Do not allow
airbag system components to come in
contact with cleaning solutions or grease. Never sub-
ject
airbag components to temperatures above 167°F
(75°C). When reconnecting the battery, no person
should be inside the vehicle.
Always place an
airbag unit that has been removed
from its
packaging with the paddedside facing upward.
Do not leave an
airbag unit unattended.
0 If the airbag unit or airbag control module has been
dropped from a height of
'/? meter (I//: ft.) or more, the
airbag unit should not be installed.

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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

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Airbag System (SRS)~
MRS control module, replacing
- Disconnect negative (-) cable from battery and cover nega-
tive terminal with insulating material.
CAUTIOI\C
Prior to disconnecting the battery, read the battery discon-
nection cautionsgiven in001 General Warnings and
Cau-
tions.
- Remove center console between front seats. See 513 lnteri-
or Trim.
Remove module mounting nuts (arrows) and lift up control
module. Disconnect electrical harness connector.
Installation is reverse of removal.
Be sure that MRS control module ground cable is attached
to the module mounting stud.
Side-impact crash sensor, removing and
installing
- Make sure ignition key is OFF.
- Remove front seat. See 520 Seats.
Remove plastic door sill trim by lifting to release clips at one
end, then sliding off. Fold up carpet towards rear seat floor. If
necessary, remove floor level heater duct.

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721 -8
(Airbag System (SRS)
4 Remove electrical harness connector from crash sensor (A).
Remove sensor retaining screws (6) and remove sensor.
Note direction of sensor before removing.
- Installation is reverse of removal,
NOTE -
Arrow on sensor must point to door sill.
Driver airbag, removing and installing
- Disconnect negative (-) cable from battery and cover nega-
tive terminal with insulating material.
WARNING-
After disconnecting the batter)! wait 5 seconds before begin-
ning work on
airbag components.
CAUTION-
Prior to disconnecting the batter)! read the battery discon-
nection cautionsgiven
in001 General Warnings and Cau-
tions.
4 Multifunction (MFL) steering wheel:
. Working behind steering wheel, completely loosen Torx
screws
(T30) while holding airbag in place.
Support
airbag unit to prevent it from falling out.

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721 -9
Airbaq System ~SRS)~
4 Sport steering wheel:
Insert screwdriver through opening in rear of steering
wheel and push against spring tension to release
airbag
unit lock.
Repeat procedure on other side of steering wheel.
Lift off
airbag unit and detach electrical harness connec-
tors.
WARNING-
Store the removedairbag unit with the horn pad facing up.
If stored facing down, accidental deployment could propel
it violently into the air, causing injury.
Once an
airbag is removed, the car must not be driven.
Do not connect the battery with the
airbag disconnect-
ed. A fault code will be stored, setting off the
airbag in-
dicator light Special tools are needed to reset the fault
memory
Once the
airbag unit is installed and all other service
procedures have been completed, start the engine and
check that the
airbag indicator light goes out. If the in-
dicator light stays on, the
airbag system will not func-
tion as designed. Have the system diagnosed and
repaired by an authorized
BMW dealer.
- Installation is reverse of removal.
MFL steering wheel: Torque airbag using specification list-
ed below.
- Sport steering wheel: Press airbag unit mounting pins into
spring
loclts in steering wheel until they snap in firmly.
CAUTION--
Do notpinch airbag harness in center of steering wheel when
installino
airbaa.
Tightening torque
Airbao to steerino wheel IMFL) 8 Nm (71 in-lb)
Passenger airbag, removing and installing
- Disconnect negative (-) cable from battery and cover nega-
tive terminal with insulating material.
--
WARNING -
After disconnecting the batteg wait 5 seconds before begin-
nina work on airbaa components.
Prior to disconnecting the battery, read the battery discon-
nection cautionsgiven in001 General Warnings and
Cau-

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721 -1 0
/Airbag System (SRS)
4 Pry up cover from top of passenger side airbag on dash-
board.
4 Remove airbag mounting bolts (arrows)
- Lift airbag and disconnect electrical harness connector. Re-
move
airbag.
WARNING-
Store the removed airbag unit with the soft pad facing up. If
stored facing down, accidental deployment could propel it vi-
olentlv into the
ail: causino inium
- Installation is reverse of removal. Make sure wiring harness
is not pinched when installing
airbag unit in dashboard.
Tightening torques
-
Passenger alr bag to 10 NM (88 in-lb)
dashboard (Me)
Door mounted side-impact airbag,
removing and installing
- Disconnect negatlve (-) cable from battery and cover nega-
tive terminal with insulating material.
CAUTION-
Prior to disconnecting the battea read the battery discon-
nection cautions given
in 001 General Warnings and Cau-
tions.
- Remove inside door panel as described in 41 1 Doors

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721 -1 1
Airbag System (SRS)~
Front door airbag:
Remove airbag mounting bolts (arrows).
Disconnect electrical harness connector.
CAUTIOI\C
When removing andinstalling the airbag unit, pay attention to
the routing
of the electrical harness to avoid kinks or breaks
in the wire.
Installation is reverse of removal,
Rear door
airbag:
Detach electrical harness connector.
Remove mounting bolts and remove
airbag from door.
- Installation is reverse of removal.
Route electrical harnesses as they were before.
Use new wire ties as necessary.
Use new self-locking mounting bolts.
Tightening
torque
Side-impact airbag to door 8.5 Nm (75 in-lb)
Head protection airbag
components
1. B-pillar deflection plate
2. Head protection airbag
3. Cable holder
4. Gas generator

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721-12
Airbag System (SRS)
Head protection airbag (HPS)
4 Replacement of a head protection airbag (HPS) is an exten-
sive operation, including removal of the following:
Complete dashboard
Complete headliner
Windshield pillar (A-pillar) trim
Door pillar (B-pillar) trim
- Before starting work on the HPS airbag, disconnect negative
(-) cable from battery and cover negative terminal with insu-
lating material.
Prior to disconnecting the battery, read the battery discon-
nection cautionsgiven in001 General Warnings and Cau-
tions.
Tightening torque HPS
airbag to body 11 Nm (8 ft-lb)
HPS airbag mounting bracket
to A or B-pillar
HPS gas generator to
dashboard reinforcement
(M6
self-tapping screw) 2.5
Nm (22 in-lb)
4 Nm (35 in-lb)

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INDEX 'tl
WARNING
Your common sense, good
judgemenl, and general alertness are
crucial to sale and successiul service
worlr. Belore attempting any work on
your
BMM be sure lo read 001
General Warnings and Cautions
and the
copyriglll page at the front 01
the manual. Review these warnings
and
caulions each lime you prepare
lo work on your BMW. Please also
read any warnings and cautions that
accompany
tile procedures in the
manual.
312-way valve (running losses)
see Fuel tank
Abbreviations, commonly used 600-14
ABS (antilock brake system)
see
Bral(es
A/C air distribution motors
see stepper motors (below)
blower final stage (resistor pack),
replacing
640-16
blower, removinglinslalling
640-1 5
compressor, replacing
640-24 condenser, replacing 64045
control panellmodule, removing1
installing
640-1 1
evaporakr, removinglinstalling 640-29
evaporator temperature sensor
640-12 expansion valve, removinglinstailing
640-27
IHKA/ IHKR system description 640-5
receiveridrier, replacing 640-26
stepper motors 640-1 3 ventilation microiilter, replacing
020-22. 640-17
see also Heating
Accelerator
iinlcage
see Maintenance
Activated carbon canister
see Fuel tank
ADS (auxiliary throttle valve)
130-57
Air compressor
330-44
Air conditioning
see
AIC
Air distribution (flap) motors
seeNC, stepper motors
Air filter see Maintenance
Air spring
300-6, 330-12
Airbag system (SRS)
2-stage
airbag 721-4
control module, replacing 721-7 driver airbag, removinglinstalling
721-8
iiead protection airbag 721-12 components 721-1 1
indicator
lighl721-4
passenger airbag, removinglinstalling
721-9 side-impact airbags crash sensor,
replacing
721-7
Airflow sensor see 130 under appropriate
fuel
injection system
Air pump
see 130 under appropriate fuel
injection system, secondary air
injection system
Air suspension
see Electronic height control
(EHC)
Alarm
see Anti-theft alarm
Alignment see
Wheei alignment
Aluminum suspension components
300-2
Antenna 650-6
Alternator see Battery, starter, alte rnator
Amplifier
650-4
Anti-theft alarm (DWA)
515-24 emergency disarming 515-31
Antifreeze (engine coolant)
see Maintenance
see also Cooling system
Antilock brake system (ABS) see Brakes
ASC see Brakes
ATF (automatic transmission fluid)
see Automatic transmission
see also Cooling systern
Automatic headlight adjustmenl
(LWR) see Lights
Automatic seat belt tensioner
720-4
Automatic shiftloclc
see
Gearshift
Automatic transmission
applications
200-3, 240-4
ATF 020-10, 200-4
capacity 240-8 checking 240-6
drainingifilling 240-7
heat exchanger 170-5
fluid pan and strainer 240-9 gearshift
see Gearshift
ID tag
200-3 range switch 610-6
removaliinstallation 240-10
steptronic see Gearshift
Auxiliary cooling fan
see
Coollng system, electric Ian
Auxiliary throttle valve (ADS)
130-57
Axle joint
see Drive axle
Back-up light switch
automatic transmission see Automatic transmission. range switch
- .~.~~~
manual transmission 230-8 -
- I