1997 BMW 540i Ele

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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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- -
On-Board Diagnostics
Professional diagnostic scan tools available atthe time of this
printing include the BMW factory tools
(DISplus, GTI,
MoDiC) and a small number of aftermarket BMW-specific
tools. See
020 Maintenance.
In addition to the professional line of scan tools, inexpensive
generic OBD
II scan tool software programs and handheld
units are readily available. Though limited, they are
nonetheless powerful diagnostic tools. These tools read live
data streams and freeze frame data as well as a host of other
valuable diagnostic data.
Diagnostic monitors
Diagnostic monitors run tests and checks on specific
emission control systems, components, and functions.
A complete drive cycle is requiredforthe tests to bevalid. See
Drive cycle in this repair group. The diagnostic monitor
signals the
ECM of the loss or impairment of the signal or
component and determines if a signal or sensor is faulty
based on
3 conditions:
* Signal or component shorted to ground
Signal or component shorted to
B+
Signal or component missing (open circuit)
The OBD
II system monitors all emission control systems that
are installed. Emission control systems vary by vehicle model
and year. For example, a vehicle may not be equipped with
secondary air injection, so no secondary air readiness code
would be present.
OBD
II software monitors the following:
Oxygen sensors
Catalysts
Engine misfire
- Fuel tank evaporative control system
Secondary air injection Fuel system
Oxygen sensor monitoring. When driving conditions allow,
response rate and switching time of each oxygen sensor is
monitored. The oxygen sensor heater function is also
monitored. The OBD
II system differentiates between
precataylst and post-catalyst oxygen sensors and reads each
one individually. In order
forthe oxygen sensor to be
effectively monitored, the system must be in closed loop
operation.

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On-Board Diagnostics
Catalyst monitoring. Thisstrategy monitors the outputofthe
precatalyst and post-catalyst oxygen sensors, comparing the
oxygen content going into the catalytic converter to the
oxygen leaving the converter.
The diagnostic executive
lknows that most of the oxygen
should be used up during the oxidation phase. If it detects
higherthan programmed values, afault is set and the MIL
illuminates.
Misfire detection. This strategy monitors crankshaft speed
fluctuations and determines if an enoine misfire occurs bv
monitoring variations in speed between each crankshaft
sensortrigger point. This strategy is so finely tuned that it can
determine the severity of the misfire.
The system determines
if a misfire is occurring, as well as
other pertinent misfire
information such as:
Specific
cylinder(s)
Severity of the misfire event
Emissions relevant or catalyst damaging
Misfire detection is an on-going monitoring process that is
only disabled under certain limited conditions.
Secondary air injection monitoring. Secondary air
injection is used to reduce HC and CO emissions during
engine warm up. Immediately following a cold engine start
(-1 0" to 40°C), fresh air (and therefore oxygen) is pumped
directly into the exhaust
manifold. By injecting additional
oxygen into the exhaust manifold, catalyst warm-up time is
reduced.
Secondary air system components are:
Electric air injection pump
* Electric pump relay
* Non-return valve
Vacuum
I vent valve
- Stainless steel air injection pipes
Vacuum reservoir
The secondary air system is monitored via the use
of the pre-
catalyst oxygen sensors. Once the air pump is active and air
is injected into the system, the signal at the oxygen sensor
reflects a lean condition. If the oxygen sensor signal does not
change, a fault is set and the faulty
bank(s) identified. If after
completing the next cold startafault is again present, the MIL
illuminates.

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On-Board Diagnostics
l~utornatic transmission diagnostic trouble codes (continued) -
P-code /BMW-FC I DTC Definition - PO732
PO732
PO733
PO733
PO733
PO733
PO734 -
I I
I I
PO742 / 48 l~orque Converter Clutch Circuit Stuck On
PO734
100
132
53
57 122
133
54
PO735
PO735
PO735
PO740
PO740
PO740
PO741
I I
PO743 14 l~or~ue Converter Clutch Circuit Electrical
Gear
2 Incorrect Ratio
Gear 2 Incorrect Ratio
Gear 3 incorrect Ratio
Gear 3 Incorrect Ratio
Gear 3 Incorrect Ratio
Gear 3 Incorrect Ratio
Gear 4 Incorrect Ratio
Gear
4 Incorrect Rat10 PO734
I I
PO743 132 l~or~ue Converter Clutch Circuit Electrical
PO734 1134 IGear 4 Incorrect Ratio
123
55 101
135
4
48 111
48 Gear 5 Incorrect Ratio
Gear 5
Incorrect Ratio
Gear 5 Incorrect Ratio
Torque Converter Clutch
Circuitlopen
Torque Converter Clutch Circuitlopen
Torque Converter Clutch Circuitlopen
Torque Converter Clutch Circuit Performance or Stuclc Off
PO745
PO748
PO748
PO750
PO751
PO751
I I
PO755 117 IShift Solenoid '8' I
PO752
PO753
PO753
PO756 117 I~hift Solenoid '8' Performance or Stuck Off I
1
1
5
16
6 16 Pressure Control Solenoid 'A'
Pressure Control Solenoid 'A' Electrical
Pressure Control Solenoid
'A' Electrical
Shift Solenoid
'A'
Shift Solenoid 'A' Performance or Stuck Off
Shift Solenoid
'A' Performance or Stuck Off
16
16
30 Shift
Solenoid
'A' Stuck On
Shift Solenoid 'A' Electrical
Shift Solenoid
'A' Electrical
PO757
PO758
PO758
PO760
PO761
17
17
33 18
18 Shift
Solenoid '8' Stuclc On
Shift Solenoid
'8' Electrical
Shift Solenoid
'8' Electrical
Shift Solenoid
'C'
Shift Solenoid 'C' Performance or Stuclc Off