1997 BMW 540i Harness

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01 0-1 0
General
Electrical testing
Many electrical problems can be understood and solved with
only a little fundamental knowledge of how electrical circuits
function.
Electrical current
only flows in a complete circuit. To operate.
every electrical device in the car requires a complete circuit
including a voltage source and a path to ground. The positive
(+) side of the battery is the original voltage source, and
ground is any return path to the negative
(-) side of the bat-
tery, whether through the wiring harness or the car body. Ex-
cept for portions of the charging system, all electrical current
in the car is direct current (DC) and flows from positive
(+) to
negative
(-).
4 Switches are used to turn components on or off by complet-
ing or interrupting the circuit.
A switch is "open" when the cir-
cuit is interrupted, and "closed" when the circuit is completed.
See
600 Electrical System-General for electrical trouble-
(LW, 1 shooting
Wire repairs
Light bulb
(consumer) ' - Repairs to a wiring harness require special care to make the
repair permanent. The wire ends must be clean.
if frayed or
Car body otherwise damaged, cut off the end and remove enough insu- (ground) i Battery lation to complete the repair. if the wire is too short, splice in a BOZLiEL new piece of wire of the same size and make two connec-
tions.
Use connectors that are designed for the purpose. Crimped
on orsoldered-on connectors are best. Crimp connectors and
special crimping pliers are widely available. If soldering, use
needle nose pliers to hold the wire near the solder joint and
create a "heat dam". This keeps the heat and the solder from
traveling up the wire. Always use a solder made specifically
for electrical
work (rosin core).
NOJE-
Twisting wires together to make a repair is not recommend-
ed. Corrosion and vibration will eventually spoil the connec-
tion and may lead to irreparable damage to sensitive
electronic components.
Insulate the finished connection. Electronics stores can sup-
ply heat-shrinkable insulating tubing that can be placed on to
the wire before connecting, slid over the finished joint, and
shrunic to a tight fit with a heat gun or hair dryer. The next best
alternative is electrical tape. Make sure the wire is clean and
free of
solder flux or other contamination. Wrap the joint tight-
ly to seal out moisture. See
600 Electrical System-General
for more information.

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Maintenance
continue to operate as designed. Extending the replacement
interval may void the emission control warranty coverage.
See
180 Exhaust System for information on replacing the
oxygen sensors.
Tightening torque
Oxvoen sensor to exhaust
manifold 50 Nrn (37 ft-lb)
NOTE-
A special soclet for replacing the oxygen sensor is available
from most automotive parts stores. The soclet has
a groove
cut down one side to allow the sensor to be installed without
damaging the wire harness.
Power steering fluid, checking level
The power steering system is permanently filled and does not
have a drain. Routinely adding ATF is not required unless the
system is leaking.
4 To check power steering fluid level in fluid reservoir:
Park car on level ground with engine off.
Level is correct
if it is between MlN and MAX marks on
dipstick.
If level is below
MlN mark, add fluid to reservoir to bring
level up.
* Hand-tighten reservoir cap.
Power steering fluid
Dexron
1iiO ATF or equivalent
Spark plugs
E39 models through model year 1998 were equipped with
spark plugs with two electrodes. These are gapped to
0.7 mm
(0.028 in) by the manufacturer and are not adjustable.
Starting with 1999 models, long life spark plugs with
3 or four
electrodes were used. These can be retroactively fitted to
earlier
models. The recommended spark plug replacement
interval
forthese is 100,000 miles.The electrode gap in these
spark plugs is not adjustable.
Spark plug applications
M52 Bosch FBLDCR
M52 TU, M54 Bosch FGR7DQP or NGK BKRBEQUP
M62 to 7/97 Bosch F7LDCR or NGK BKR6EK
M62 from 7/97 Bosch F9LDCR
M62 TU Bosch FGR7DQP or NGK BKRGEQUP

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020-21
Maintenance
Spark plugs, replacing
E39 engines use a coil-over-spark plug configuration, with
one ignition coil above each spark plug. Sparks plugs should
be removed only after the engine has cooled.
Remove engine
cover(s) over ignition coils:
Remove acoustic cover over fuel injectors
I intake
manifold.
6-cylinder engine: Remove oil filler cap.
Remove plastic trim covers (arrows).
Remove cover hold-down bolts. Remove coil
cover(s)
6-cylinder engine: Temporarily reinstall oil filler cap to
keep out contaminants.
Remove ignition coil grounding harnesses (arrows). 6-cylin-
der coils shown,
V-8 engine is similar.
< Remove ignition coils:
Pull up on spring clips to disconnect ignition coil harness
connectors.
Remove coil mounting bolts. Pull coils up and off spark
plugs.
- Remove spark plugs.

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Two common causes of driveability problems are incorrect
system voltage and bad grounds.
System voltage
Digital motor electronics (DME) requires that the system (bat-
tery) voltage be maintained within a narrow range of DC volt-
age.
DC voltage levels beyond or below the operating range,
or any
AIC voltage in the electrical system can cause havoc.
When troubleshooting an illuminated MIL, make sure the bat-
tery is fully charged and capable of delivering all its power to
the electrical system. An undercharged battery can amplify
AIC alternator output ripple.
To
make a quick check of the battery charge, measure the
voltage across the battery terminals with all cables attached
and the ignition off.
Afully charged battery will measure 12.6
volts or slightly more, compared to 12.1 5 volts for a battery
with a 25% charge.
The DME system operates at low voltage and current levels,
making it sensitive to small increases in resistance. The elec-
trical system is routinely subjected to corrosion, vibration and
wear, so faults or corrosion in the wiring harness and connec-
tors are not uncommon. Check the battery terminals
forcorro-
sion or loose cable connections. See 121 Battery, Starter,
Alternator for additional information.
If a battery cable connection has no
v~sible faults but is still
suspect, measure the voltage drop across the connection. A
large drop indicates excessive resistance, meaning that the
connection is corroded, dirty, or damaged. Clean or repairthe
connection and retest.
NOTE-
For instructions on conducting a voltage drop test and other
general electrical troubleshooting information, see
600 Elec-
trical System-General.
Visually inspect all wiring, connectors, switches and fuses in
the system. Loose or damaged connectors can cause inter-
mittent problems, especially the small terminals in the ECM
connectors. Disconnect the wiring harness connectors to
check for corrosion, and use electrical cleaning spray to re-
move contaminants.
Main grounds
Good grounds are critical to proper DME operation. If a
ground connection has no visible faults but is still suspect.
measure the voltage drop across the connection. A large volt-
age drop means high resistance. Clean or repair the connec-
tion and retest.
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11 0-4
/Engine Removal and Installation
- Disconnect negative (-) cable from battery.
CAUTION- Prior to disconnecting the
batteg read the battery discon-
nection cautions
in 001 General Cautions and Warnings.
- Remove engine hood, or place in service position. See 410
Fenders, Engine Hood.
4 Remove left and right interior ventilation ducts (lefl side
shown):
Release ventilation filter cover latch (A) and remove cover.
Release plastic loclting tab
(6) or release locking tabs on
top of duct (later models).
Rotate duct counterclocltwise to
unloclt from bulkhead and
remove (arrow).
Disconnect electrical harness from hood switch (C).
Release spring
loclt (D).
Slide filter housing away from inner fender to remove.
Removal of right side ventilation duct is similar.
Remove rear bulkhead panel:
Remove rubber sealing gasket (arrow).
- Remove 3 mounting clips (A).
Remove
4 retaining screws (6).
Lift off panel.
Remove complete air filter housing:
Loosen
intalte duct hose clamp (A) at throttle assembly.
Loosen clamp and remove idle control line from intalte duct
(6) and (where applicable) disconnect idle speed control
valve electrical harness connector.
Disconnect harness connector (C) from mass air flow sen-
sor.
Remove air filter housing mounting screw (D).
Disconnect vent tube
(E).
Loosen air intake duct clamp (F).
Carefully lift air filter housing out of engine bay.

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Engine Removal and lnstallationl
< Remove positive battery cable and intake manifold cover:
Remove protective cover from positive (+)jump start post
(4.
Loosen and remove battery lead mounting nut.
Remove lead and push down through intake manifold
Remove trim covers
(arrows) from fuel injector cover.
Remove cover hold down bolts and lift off cover.
Working above engine, disconnect the following:
Vent line from cylinder head cover (A).
M52 engine: Oxygen sensor connectors (8).
Electrical harness connector from intalte camshaft VANOS
solenoid valve
(C).
M52 engine: Disconnect electrical harness connectors at
throttle valve position switch
(D), ASC valve position switch
(E), fuel injector harness (F) and vent valve (G).
CAUTION-
Be sure to mark oxygen sensor harness connectors so that
they can be reassembled correctly Do not interchange con-
nectors.
4 M52 TU, M54 engine: Disconnect fuel injector electrical con-
nectors from injectors.
Use small screwdriverto pry one corner of wire lock clip on
fuel injector
1 connector.
Repeat for all injectors.
Lifl off connector loom and lay aside.

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110-8
1 Engine Removal and Installation
4 M52 TU, M54 engine: Remove fasteners (arrows) retaining
wiring harness conduit to throttle body.
4 M52 TU, M54 engine: Working at throttle housing, rotate har-
ness plug (arrow) counterclockwise and remove.
4 M52 TU, M54 engine: Disconnect electrical harness connec-
tor at idle speed control valve (arrow), directly above throttle
valve.

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Engine Removal and lnstallationl
M52 TU, M54 engine: Disconnect electrical harness connec-
tor at fuel tank venting valve
(A). Disconnect vent hose at fit-
ting (arrow).
- Working under intake manifold, disconnect the following:
Engine oil dipstick tube support.
Oil separator return line from
dipsticlc tube.
Intake air temperature sensorelectrical harness connector
(underside of intake manifold near throttle body).
M52 TU, M54 engine: Resonance valve electrical harness
connector.
M52 engine: Fuel tank vent line and harness.
< Working underneath car, remove lower intalte manifold sup-
port mounting bolts (arrows).
4 M52 TU. M54 engine: Remove fuel rail mounting bolts
(arrows):
Carefully pry fuel rail off manifold.
Separate fuel line support bracket at rear of intake
manifold.
NOTE-
* M52 TU engine shown. M54 engine is similar.
M52 engine: Fuel rail is removed with intalte manifold.