fuse BMW 540i 1997 E39 Workshop Manual

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General Tightening fasteners
When tightening the bolts ornuts on acomponent, it is always
good practice to tighten the bolts gradually and evenly to
avoid misalignment or over-stressing any one portion of the
component. For components sealed with gaskets, this meth-
od helps to ensure that the
gasket will seal properly.
WARNING
-
Table a: General bolt tightening torques in Nm (max.
permissible) is
a general reference only The values listedin
the table are not intended to be usedas a substitute for tor-
ques specifically called out in the text or in manufacturer's in-
formation.
4 Where there are several fasteners, tighten them in a se-
NOTE-
* Metric bolt classes or grades are rnarlced on the bolt head.
* Do not confuse wrench size with bolt diameter. Fora listing
of the common wrenches used on various bolt
diameters,
see Basic tool requirements.
2 BOO~FNG
quence alternating between opposite sides of the compo-
nent. Repeat the sequence until all the bolts are evenly
tightened to the proper specification.
For some repairs a specific tightening sequence is
neces-
sary, or particular order of assembly is required. Such special
conditions are noted in the text, and the necessary sequence
is described or illustrated. Where no specific torque is listed,
Table
a: General bolt tightening torques in Nm (max. per-
missible) can be used as a general guide for tightening fas-
teners.

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Spare parts kit
Carrying a basic set of spare parts can prevent a rninorbreak-
down from turning into a major repair annoyance. The list be-
low is a good place to start.
Spare parts kit
- basic
Polyribbed drive
belt(s)
BMW engine oil: one or two quarts
BMW engine coolant:
1 gallon of premixed 50150 BMW
anti-freeze and water
Fuse assortment:
7.5A. IOA, 1 5A, 20A, 30A. 50A
Radiator hoses: upper and lower
Spare parts
kit - additional contents
Exterior lighting bulbs: headlight, bralte light, turn signal,
and taillight
* Wiper blades or blade inserts
Brake fluid: new, unopened bottle, DOT
4 specification
Main relay for DME 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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- -
Battery, Starter, Alternator
This section covers the battery, alternator, starter and associ-
ated components of the electrical system.
Troubleshooting information
forthese components isfound in
Table a. Battery, alternator and starter troubleshooting.
For additional electrical troubleshooting information, see
600 Electrical System-General.
Special tools
4 Automotive digital multimeter
CAUTION-
Only use a digital multirneter when testing automotive electri- I) cal components.
4 Closed-circuit current measurement adaptor
(Tool No.
BMW 61 2 300)
Engine electrical system
The alternator and starter are wired directly to the battery. To
prevent accidental shorts that might blow a fuse or damage
wires and electrical components, always disconnect the
negative
(-) battery cable before working on the electrical
system.
Various versions of alternators, voltage regulators, starters,
and batteries are used in
E39 cars. Replace components ac-
cording to the original equipment specification.

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Battery, Starter, ~lternatorl
@ TO fuse & relay panel Battery Safety Terminal
A Battery Safety Terminal (BST) controlled by the Multiple
Restraint System (MRS) control unit was introduced for mod-
el year 1998
vehicles. The system will disconnect electrical
power to the engine compartment
in the event of a significant
impact. The MRS system fires an encapsulated pyrotechnic
device
in the positive (+) battery terminal that disconnects
power to the engine compartment, but maintains power to
the exterior lights and interior of the vehicle.
point
002125~1
Table a. Battery, alternator and starter troubleshooting
1-
/Starter motor or solenoid faulty. l~est starter.
Symptom
Engine does not crank
Engine cranks slowly or
not at all, solenoid
clicits
when starter is operated.
I I
Battery will not stay IShort circuit draining battery. l~est for excessive current drain with everything
Probable cause
Fault
in immobilizer system (EWS)
-Clean Battery cables loose, dirty or corroded.
Battery discharged.
Battery to body ground cable in trunk
loose,
dirty or corroded
Poor connection at starter motor terminal
30.
Corrective action
Try another ignition key. If problem persists, contact
your authorized BMW dealer.
or replace cables. See 020
~aintenance.
Charge battery and test. Replace if necessary.
inspect ground cable. Clean, tighten or replace if
necessary.
Checlc connections, test for voltage at starter. Test for
voltage at neutral safety or clutch
interloclc switch.
charged more than a few
days.
I~atter~ faulty. /Test battery and replace if necessary.
Short driving trips and high electrical drain
on
charging system does not allow battery to
recharge.
. I
I Battery cables loose, dirty or corroded. Iclean or replace cables. See 020 Maintenance.
Evaluate driving
style. Where possible, reduce
electrical
consumption when malting short trips.
Drive
belt@) loose, worn or damaged.
IAlternator or voltage regulator faulty. /Test alternator and voltage regulator.
Inspect
or replace ribbed
belt@). See 020
Maintenance.

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- -
/Battery, Starter, Alternator -- - -. - --I
< Check for battery voltage at alternator terminal 30 (B+) (ar-
row):
Pull back rubber insulating cover at terminal 30 at rear of
alternator.
Connect voltmeter between terminal 30 and ground and
check for battery voltage.
If voltage is not present, check
wiring for faults.
NOTE-
On V-8 engines, access to the rear of the alternator is limited.
Check for battery voltage between the jump start post on the
left cylinder head and ground.
r Disconnect harness connector from alternator. Turn ianition
on and check for battery voltage between terminal
lgand
ground. If voltage is not present, check wiring and fuses for
faults.
Reconnect connector to alternator.
Locate the blue wire coming from terminal
61E of the alter-
nator connector. Carefully connect the positive
(+) test lead
to the wire using a piercing test lead end.
Turn ignition key on and check for voltage. Voltage should be
less than 1.5 VDC and charge indicator lamp should light.
- Making sure all test equipment and tools are clear, start en-
gine. Voltage should increase to
8.0 VDC or higher. The
charge indicator light should go out.
If voltage does not increase and system is not charging,
the fault is in alternator.
- If voltage does not increase, but system is charging, inter- - roaate svstem for faults usina an appropriate BMW scan - .. . tool and'reset fault memory.
- If a load tester is not available, a quick alternator output test
can be done by running engine at about 2000 rpm and turn-
- -
ing on electrical loads (fans, lights, rear window defroster, -
- and wipers). With all accessories on, battery voltage should
be above 12.6
V.

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Fuel Injection 1
Working in right rear of engine compartment:
Release interior ventilation filter cover latch
(A) and re-
move cover.
Release plastic locking tab
(6).
Rotate duct inward (arrow) to unlock from bulk head and
remove duct.
Release spring
lock (C) to remove lower iilter housing.
Slide filter housing away from inner fender to remove.
- Remove electrical box (E-box) cover fasteners and remove
cover.
NOTE-
OBD I1 fault memory (including an illuminated MIL) can
only be reset using an electronic scan tool. Removing the
connector from the ECM or disconnecting the battery will
not erase the fault
memory.
The BMW-dedicated 20-pin diagnostic linlc connector
(DLC) is in the right rear of the engine compartment.
The 16-pin OBD
I1 diagnostic connector (arrow) is located
inside the car on the lower left dash panel.
ECM relay, testing
Fuses lor ECM In E-bbx 502130488
4 The engine control module (ECM) relay is energized via the
ECM and supplies battery positive
(B+) power to many of the
engine management components and subsystems.
If this re-
lay is faulty, the engine will not start.
Relay positions can vary. Be sure to confirm relay position by
identifying the wiring in the socket using the wiring diagrams
in
ELE Electrical Wiring Diagrams.
NOTE-
The ECM relay is also referred to as the DME main relay.

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130-8
Fuel Injection
With ignition off, remove main relay (K6300) (arrow) in
E-box.
- With ignition on and relay installed, check for battery voltage
on terminal
2 (87).
4 Check for voltage at terminal 8 (30) on relay socket.
If battery voltage is present, relay has energized and is
functioning correctly.
Gmund from 6L (hot ~4th k~y key in Ern
2I '1
on position)
to
Fuel pump RdiWt Rd from Battery and other system components SOZI~O~~I~Y
If battery voltage is not present and all earlier tests are OK,
relay is faulty and should be replaced.
If
battery voltage is present continue testing.
If battery voltage is not present, check fuse 109 (80-amp
fusible link) under passenger seat carpet. See ELE Elec-
trical Wiring Diagrams.
- Reinstall relay and turn ignition on. Gain access to back side
of relay socket and check for ground on terminal
4 (85).
If ground is present continue testing.
If ground is not present, signal from ECM is missing. Check
NOTE-
If no faults are found during testing but power is not reaching
the
ECM or other components, check the fuses in the fuse
carrier
X8680 in the E-box.
wire
between ECM and relay.

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130-1 3
Fuel Injection I
< Unplug harness connector (arrow) from sensor.
CAUTION-
Be sure ignition is OFF before disconnecting or reconnecting
DME system components.
NOTE-
Do not confuse the throttle position sensor on the main Nirot-
tle body with the throttle position switch on the secondary
throttle body, where applicable.
- Remove two mounting screws holding sensor to throttle
housing.
- Installation is reverse of removal. Clear adaptation settings
from ECM using BMW-compatible scan tool.
NOTE-
Poor idle quality may be noticeable for a period if the adapta-
tion settings are not cleared after installing new TPS.
ldle speed control valve,
checking and replacing
The idle speed control valve regulates idle speed by redirect-
inq airaround the throttlevalve.The idlespeed control valve is
mounted on the underside of the intake manifold adjacent to
the dipstick tube bracket. Accessing the valve is best accom-
plished by first removing the air filter housing and the throttle
body assembly.
The valve issupplied with
batteryvoltagefrom the ECM relay.
The idle speed control valve incorporates a two-coil rotary ac-
tuator. The ground sides of each coil are pulsed
sirnulta-
neously by the ECM. The duty cycle of each circuit is varied to
achieve the required idle speed.
Afaulty ldle speed control valve sets afault code and the MIL
is illuminated when
OED II fault criteria are exceeded.
Before checking the idle speed control valve, confirm that the
throttle position sensor is working correctly.
- With engine running, check that idle speed control valve is
buzzing.
- Turn on AIC system or shift transmission into drive. ldle
should remain steady or increase slightly.

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130-28
Fuel Injection
ECM Relay
4 Check for voltage at terminal 6 (30) at reiay socket
If battery voltage is present continue testing.
if battery voltage is not present, check fuse 109 (80-amp
fusible link) under passenger seat carpet. See 610 Electri-
cal
Component Locations.
- Reinstall relay and turn ignition on. Gain access to back side
of reiay socket and check for ground at terminal
4.
If ground is present continue testing.
If ground is not present, signal
from ECM is missing. Check
wire between ECM and relay.
- With ignition on and reiay installed, check lor battery voltage
at terminal
2.
If battery voltage is present, relay has energized and is
functioning correctly.
If battery voltage is not present and
ail earlier tests are OK,
relay is faulty and should be replaced.
NOTE-
If no faults are found during testing but power is not reaching
the ECM or other components, check the fuses
in the fuse
carrier
X8680 in the E-box.
Mass air flow (MAF) sensor, checking and
replacing
4 The hot f~lm mass air flow (MAF) sensor sends a varying volt-
age (approx. 0.5 - 4.5 vdc) to the ECM representing the mea-
sured
Intake air. The alr mass input signal is produced
electron~caily uslng an electrically heated metal fllm in the air
flow stream.
The ECM relay provides the operating voltage to the MAF
sensor. As air
flows through the sensor, the film is cooled. To
maintain the film at a constant temperature, additional current
is necessary. It is this additional current that is the basis lor
the input signal.
If there is no output signal from the MAF sensor, the ECM op-
erates the engine using the throttle position and engine rpm
inputs. A faulty MAF sensor illuminates the MIL.