1999 BMW 540i Electrical System

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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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100-6
( Engine-General
The main grounds for the fuel and ignition circuits of the DME
system are illustrated below; see 610 Electrical Component
Locations for additional ground and component locations.
4 Ground for engine management system in right rear of en-
gine compartment on E-box bulkhead (arrow).
6-cylinder models: Grounds
for ignition coils (arrows)
4 V-8 models: Grounds for ignition coils, at cylinders 3
(arrow) and 7.
4 Fuel pump ground (arrow) below right tail light in luggage
compartment.
NOTE-
Ground location for sedan shown, wagon models may
differ.

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110-12
Engine Removal and Installation
4 Remove hoses from thermostat housing by releasing locks
(arrows). If applicable, detach electrical harness connector
for thermostat housing.
NOTE-
Two different types of hose fasteners are used on the E39
car; lock clamp type as shown above or standard band
clamps.
- On vehicles equipped with mechanical cooling fan: Remove
belt-driven cooling fan and radiator as described in
170 Ra-
diator and Cooling
System.
CAUTION-
32 mm radiator fan mounting nut has left hand threads.
4 Disconnect coolant hose (arrow) at rear left side of engine
above starter.
4 Disconnect coolant hose (arrow) at front left side of engine
mount.
- Unbolt power steering fluid reservoir and pull aside without
detaching hoses. Secure to fender with cord or stiff wire.

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Engine Removal and Installation
4 Working at E-box at right rear of engine compartment:
Disconnect engine electrical harness connectors
(arrows).
Lift off harness looms and lay over engine.
- Remove polyribbed drive belts. Mark direction of rotation if
belts will be reused. See 020 Maintenance.
- Remove exhaust system and transmission from car. See 180
Exhaust System, 230 Manual Transmission or 240 Auto-
matic Transmission.
NOJE-
Detach automatic transmission cooler lines from radiator, re-
move brackets holding lines to side of engine, andstore lines
in a clean environment.
- Remove power steering pump:
If necessary, remove steering pump pulley.
Remove front and rear pump mounting bolts.
Suspend pump from body using stiff wire.
4 Remove A/C compressor mounting bolts (arrows) and AIC
compressor from its mounting bracketwithoutdisconnecting,
distorting, or deforming any refrigerant lines. Suspend from
body using stiff wire.
4 If applicable, remove secondary air pump:
Remove hose at one-way valve
(A).
Remove bolts at support bracket on strut tower (arrows).
- Disconnect electrical harness from bottom of secondary
air pump.
Remove bracket from strut tower.

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- .. -.
-. Engine Removal and in=/
4 Remove left interior ventilation duct:
Release duct locking tabs (A). Early models: release
loclc
ing strap.
* Rotate duct inward (arrow) to detach.
Release spring
loclc (El) to unlock ventilation housing.
Disconnect electrical harness connector from hood switch
(C).
Release locking clip and remove ventilation filter cover (D).
Slide air housing away from inner fender to remove.
Removal
of right side ventilation duct is similar.
4 Remove rear engine compartment bulkhead panel:
Remove rubber sealing strip.
* Remove 3 mounting clips (A).
Remove harness supporting clip
(El).
Unlock panel retainers (arrows).
Lifl out panel.
< Separate engine wiring harness (arrow) from electrical box
at right side of engine compartment:
Remove E-box cover.
Disconnect electrical harness connectors leading from en-
gine wiring harness (arrow). Connectors are labelled (A,
El, C. D, E) for locating purposes.
Lay engine harness on top of engine.
- Drain engine coolant from engine block and radiator. See 170
Radiator and Cooling System.
Remove drain plugs from right and left side of engine
bloclc
(between cylinders 213 and 617).
Afler coolant has drained, reinstall drain plugs using new
sealing washers.
Drain radiator and reinstall drain plug.
Tightening
torques
Coolant drain plug to cylinder block (M14) 25 Nm (18 ft-ib)
Radiator drain screw to radiator 2.5
Nm (22 in-lb)

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11 0-20
Engine Removal and Installation
Working at right side of transmission bellhousing, disconnect
electrical harness connections (arrows) from starter. Re-
move starter retaining bolts and remove starter from trans-
mission mount.
M62 TU engine: Disconnect electrical harness connector
for right oxygen sensor from retaining clip and remove re-
taining clip from transmission.
- Working underneath engine compartment at left side:
Unclip positive battery cable from oil pan.
. Remove alternator cooling duct.
4 M62 engine: Remove fastener A and plug connector B from
alternator.
- M62 TU engine: Remove electrical harness connectors from
front of water cooled alternator.
- Remove exhaust system and transmission. See 180 Ex-
haust System and 230 Manual Transmission or 240 Auto-
matic Transmission.
- Working at front of engine:
Remove upper and lower hoses from radiator.
D~sconnect expansion tank hose from coolant pump.
- Remove belt-driven cooling fan:
Counterhold fan with special tool
11 5 050.
Turn fan mounting nut (32 mm) clockwise (left hand
threads) to loosen.
Rotate fan clockwise to remove.
Remove cooling fan shroud:
Disconnect electrical connectors from coolant level sensor
(B) and coolant temperature sensor (C).
. Remove expansion rivets (A) from each side of shroud
Remove coolant hose
(D).
Slide fan shroud with expansion tank up. Remove radiator
overflow tube from spout of expansion tank. Remove radi-
ator fan shroud with expansion tank.
Remove radiator. See
170 Radiator and Cooling System.

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--
-- Engine Removal and installation' -
Remove polyribbed A/C compressor belt:
Mark direction of belt travel if belts are to be reused.
Loosen bolts
(A).
Turn adjusting lug (B) clocltwise to release belt tension.
Working beneath car, remove power steering pump and air
conditioner compressor. Suspend from body using stiff wire.
Remove exhaust manifolds. See
180 Exhaust System.
< lnstall engine lifting device (BMW 11 0 000 or equivalent) to
front and rear engine supports and raise engine until it's
weight is supported. Detach engine mounts.
a Watch carefully for hoses and electrical wires that might
snag.
- installation is reverse of removal:
Replace all gaskets, O-rings and seals.
V-8 engine mounts have two sets of mounting holes. E39
cars use front most mounting holes.
* On cars with automatic transmission, use new O-rings at
ATF cooler lines.
Use new alignment sleeves when installing transmission.
Be sure engine drive belts properly engage pulley grooves.
When installing belt, preload tensioner to stop (toward
belt), then tighten tensioner clamping nut.
lnstall front exhaust pipes using new gasltets and copper
paste and new mounting hardware. See
180 Exhaust
System.
Change engine oil and filter. Check all other fluid levels as
described in
020 Maintenance.
Refill and bleed cooling system as described in
170 Radi-
ator and Cooling System.
CAUTION-
Do not interchange knoclc sensor harness connectors. Seri-
ous engine damage may result

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..
Cylinder Head Removal and Installation 1
< Remove intake throttle valve and ASC throttle assemblies:
Disconnect ASC throttle cable
(A).
- Remove ASC throttle housing mounting fasteners (B).
NOTE-
It is not necessary to disconnect coolant hoses (C) 01
bowden cables (D).
Remove intake throttle housing mounting hardware, pull
throttle housing off
intake manifold, and set aside.
- Working under intake manifold, disconnect the following:
Engine oil dipstick tube support.
Oil separator return line from dipstick tube.
Intake air temperature sensor electrical harness connector
(underside of intake manifold near throttle body).
* Fuel tank vent line and electrical harness at canister vent
valve.
Remove lower intake manifold supports (arrows).
- Disconnect coolant line retaining bracket at cylinder block.
4 Remove manifold mounting hardware (arrows).
- Remove intake manifold from cylinder head while carefully
checking for electrical connections or hoses.
NOTE-
Fuel rail is removed with intake manifold,
CAUTIOI\C
Stuff clean rags into open intake ports to prevent any parts
from falling into
Nie engine intake.
- Drain cooling system (engine block and radiator), then re-
move radiator cooling fan and fan shroud. See
170 Radiator
and Cooling System.
- Disconnect coolant hoses from thermostat housing.