1999 BMW 540i electrical

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Seats
Remove left and right side bacltrest mounting fasteners (ar-
row).
Pull up on backrest to detach from top retainers. Slide back-
rest to side to clear seat belts while removing.
NOTE-
If the car is equipped with heatedrearseats, detach electrical
harness
connector(s) as you remove the seat components.
4 When reinstalling, be sure to pull seat belts and buckles (ar-
rows) up through appropriate slots in seat cushion.
Headrest, removing and installing
- Slide headrest as far up as possible.
Press guides (arrows)
back and
Installation is reverse of removal pull
upward to remove

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-.
Sunroof
Sunroof panel, emergency closing
4 Using a plastic tool carefully pry interior light out of headliner.
4 Remove access panel from below sunroof motor by inserting
fingers through light opening and pressing down.
4 Disconnect electrical connections (arrow) and lay switch
panel aside.
4 Insert hex ltey into drive in sunroof motor (arrow), and turn
hex ltey to manually close sunroof.
NOTE-
The hex ley for manually (emergency) closing the sunroof
can be found in the tool
Itit located in the trunk lid (sedan
models) or under the cargo area floor panel (Sport Wagon).

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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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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