2000 BMW 540i warning

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120 lgnition System
...................... General
Special tools ...................
Warnings and cautions ...........
Engine management .............
................. lgnition system
Ignition system. troubleshooting
....
... Oscilloscope diagnostic diagrams
................ Misfire detection
............. Ignition System Service 120-9
.................... Ignition firing order 120-9
.............. Disabling ignition system 120-10
................... Checking for spark 120-1 0
lgnition coil assembly.
................. testing and replacing 120-1 0
.............. Crankshaftspeedsensor 120-12
............. Camshaft position sensors 120-1 4
...................... Knocksensors 120-16

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120-3
Ignition System
Warnings and cautions
The ignition system produces dangerous high voltage. In ad-
dition the sensitive electronic components can be damaged
if
proper precautions are not adhered to.
WARNING-
* Do not touch or disconnect any cables from the coils while
the engine is running or being
cranked by the starter.
The ignition system produces high voltages that can be
fatal. Avoid contact with exposed terminals. Use ex-
treme caution when working on a car with the ignition
switched on or the engine running.
- Connect and disconnect tlie DME system wiring and
test equipment leads only when the ignition is
OFF:
Before operating the starter without starting the engine
(for example when
making a compression test) always
disable the ignition.
CA
U TIOW-
Do not attempt to disable the ignition by removing the coils
from the spark plugs.
Connect or disconnect ignition system wires, multiple
wire connectors, and ignition test equipment leads only
while the ignition is
off Switch multimeter functions or
measurement ranges only with the test probes discon-
nected.
* Do not disconnect the battery while the engine is run-
ning.
A high impedance digital multimeter should be used for
all voltage and resistance tests. An LED test light
should be used in place of an incandescent-type test
lamp.
In general, make test connections only as specified by
BMW as described in this manual, or as described by
the instrument manufacturer.
Engine management
BMW €39 engines use an advanced engine management
system known as Digital Motor Electronics (DME). DME in-
corporates on-board diagnostics, fuel injection, ignition and
other engine control functions. DME variants are listed in
Table a. Engine management systems.
Second generation On-Board Diagnostics
(OED II) is incor-
porated into the engine management systems used on the
cars covered by this manual. Use a BMW-specific electronic
scan tool, or a "Generic"
OED II scan tool to access Diagnos-
tic Trouble Codes (DTCs). DTCs can help pinpoint ignition
ine management problems.

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Lnition switch
4 The positive (+) power supply to the ignition coils comes to
the ignition switch via an unloader relay. When the ignition
switch is turned on, the relay closes, to provide voltage to the
ignition coils. The coils are then actuated at the negative side
by the engine control module.
NOTE-
Schematic diagrams shown are for illustrative purposes only.
See ELE Electrical Wiring Diagrams for engine manage-
ment specific wiring information.
WARNING- Do not touch or disconnect any cables from the coils while
the engine is running or being cranked by the starter:
The ignition system produces high voltages that can be
fatal. Avoid contact with exposed terminals. Use ex-
treme caution when
working on a car with the ignition
switched on or the engine running.
* Connect and disconnect the DME system wiring and
test equipment leads only when the ignition is
OFF
Before operating the starter without starting the engine
(for example when
making a compression test), always
disable the ignition.
4 Knock sensors (arrows) monitor the combustion chamber for
engine-damaging knock. Six-cylinder models (shown) use
two sensors with each sensor monitoring three cylinders.
V-
8 models use four sensors, each monitoring two cylinders. If
engine
knock is detected, the ignition point is retarded by the
ECM.
I Ignition advance Ignition timing is electronically mapped and not adjustable.
The ECM uses engine load, engine speed, coolant tempera-
ture, knock detection, and intake air temperature as the basic
inputs for timing control.
A three dimensional map similar to
the one shown is digitally stored in the ECM.
- The initial ignition point is determined by the crankshaft
speed sensor during cranking. Once the engine is running.
timing is continually adjusted based on operating conditions.

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120-6
lgnition System
lgnition system, troubleshooting
Troubleshooting ignition system faults should begin with an
interrogation of the On-Board Diagnostics (OBD
II) system.
The OBD
II system detects ignition system misfire and other
related faults. When faults are detected, the OBD
II system
stores a Diagnostic Trouble Code (DTC) in the Engine Con-
trol Module (ECM) along with other pertinent fault information.
4 In addition, the Malfunction Indicator Light (MIL) will come on
if an emissions related fault is detected. Additional OBD
II in-
formation, including a DTC lookup table, can be found in
OED On-Board Diagnostics.
NOTE-
BMWmodels covered in this manual were equipped with one
of three versions of
MIL warning lights (as shown).
Misfire detection
Engine m~sfire in one or more cylinders, may be caused by a
var~ety of malfunctions in various subsystems. The OBD II
system ~ncorporated into the engine management systems is
des~gned to detect and warn of misfire faults during englne
operat~on. See OED On Board Diagnostics.
WARNING -
lgnition misfires can cause high hydrocarbon exhaust emis-
sions andcatalytic converter damage. For this reason, if a se-
vere misfire is detected, the fuel injector
will be turned off to
the specific cylinder and the
MIL will be illuminated. A misfire
may also produce an overheated catalytic converter, which
can be a fire hazard.
Oscilloscope diagnostic diagrams
One way to diagnose a faulty coil is to use an oscilloscope to
analyze spark quality with the engine running.
See Table b. lgnition secondary voltage diagnostics for
list of common ignition
coil voltage faults and related causes.

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120-1 2
ignition System
Crankshaftspeedsensor
Crankshaft speed sensor, replacing (M52, M52 TU and
M54 engines)
4 Crankshaft speed sensor for 6-cylinder engine is mounted in
the left rear side of the cylinder block below the starter (ar-
row). The sensor reads a toothed pulse wheel mounted to
the end of the crankshaft.
- if the Engine Control Module (ECM) does not receive a signal
from the crankshaft speed sensor during cranking, the en-
gine will not start.
- If the OBD II svstem misfire detection ~rotocol detects a cat- - - ~~
alysr oarnagin; faLlt oJe to a ma I-nclion in crandshafi speeo
sensor components. Ine Check Engine
lignr (Malfuncrion In-
dicator Light or MIL) will be illuminated.
NOTE-
If the crankshaft speed sensor pulse wheel is damaged, the
engine will have to be disassembled down to the crankshaft
to
reolace the wheel.
- Make certain ignition has been turned off.
- Raise car and support in a safe manner.
WARNING -
Make sure the car is stable and well supported at all times.
Use a professional automotive lift orjacltstands designed for
the ouroose.
A floor iaclc is not adequate support.
- Remove under engine splash guard
4 Working underneath starter:
Cut off wire tie securing crankshaft speed sensor harness
connector (arrow) to sensor.
* Disconnect harness connector.
4 Remove sensor mounting fastener (arrow) and remove sen-
sor from cylinder block.
- Installation is reverse of removal, noting the following:
Use a new O-ring when installing sensor.
Be sure wiring is routed in same orientation.
Secure sensor using new wire ties.
Use scan tool to read out and clear ECM fault memory.

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121-1
121 Battery. Starter. Alternator
General ........................... .I2 1.2
Special tools ........................ .I2 1.2
Engine electrical system ............... .I2 1.2
Battery Safety Terminal ............... .I2 1.3
Warnings and cautions ................. 121 -4
Battery ............................ 121-5
Battery testing ...................... .I2 1.5
Hydrometer testing ................... .I2 1.5
Battery open-circuit voltage test ......... .I2 1.6
Battery load voltage test ................ 121 -6
Closed-circuit current measurement ..... .I2 1.7
Battery charging ...................... 121 -9
Battery safety terminal, replacing ......... 121-9
Alternator (generator) ............. .I2 1.10
Alternator. basic .................... .I2 1.11
Alternator with multi-function
control (MFR)
...................... .I2 1.11
Water-cooled alternator ............... 121 -12
Charging System Troubleshooting . 121-12
Charging system quick-check .......... 121-13
Charging system. checking ............ 121-13
Alternator. removing and installing
(6-cylinder engine)
.................. 121 -1 5
Alternator. removing and installing
(M62 engine. air cooled)
.............. 121-16
Alternator. removing and installing
(M62 TU engine. water cooled) ......... 121-1 8
Starter ........................... 121 -1 9
Starter troubleshooting ............... 121 -1 9
Starter. removing and installing
(6-cylinder engine)
.................. 121-20
Starter. removing and installing
(V-8 engine)
........................ 121 -21
Solenoid switch. removing and installing . . 121-23

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.-. .
Battery, Starter, Alternator
Warnings and cautions
WARNING -
Wear goggles, rubber gloves, and a rubber apron when
working around the battery or battery acid (electrolyte).
Battery acid contains sulfuric acid and can cause skin
irritation and burning.
If acid is spilled on your skin or
clothing, flush the area at once with large quantities of
water. If electrolyte gets into your eyes, flush them with
large quantities of clean water for several minutes and
call a physician.
Batteries that are being charged or are fully charged
give off explosive hydrogen gas. Keep sparks and open
flames away. Do not
smoke.
CA UTIOI\C
Only use a digital multimeter when testing automotive elec-
trical components.
. If a repair procedure specifies disconnecting the bat-
tery, follow the instruction for safety reasons.
Prior to disconnecting the battery, read the battery dis-
connection cautions in
001 General Cautions and
Warnings.
Models with MS43 engine management: Allow at least
3 minutes to elapse after turning ignition ley to OFFpo-
sition before disconnecting battery. This willallow sum-
cient tinie to complete the DMJL (fuel tank pressure)
test
* Disconnecting the battery cables may erase fault codes
stored in ECM memory.
Always disconnect the negative
(-) battery cable first
and reconnect it last. Cover the battery post with an in-
sulating material whenever the cable is removed.
Do not disconnect battery, alternator or starter wires
while the engine is running.
0 Never reverse the battery cables. Even a momentary
wrong connection can damage the alternator or other
electrical components.
Do not depend on the color of insulation to tell battery
positive and negative cables apart. Label cables before
removing.
The slide-tilt sunroof may fail to function properly
after
disconnecting and reconnecting the battery. Reinitial-
ize sunroof as described in 540 Sunroof.

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Battery, Starter, ~lternatorl
WARNING-
Always wear protective goggles and clothing when perform-
ing a load test.
Table
d. Battery load test - minimum voltage
Ambient temperature Voltage*
27
" C (80" F) 9.6 V
-I 8' C (0"
F) 8.5 V
* Measure
after applying a 200 amp load for 15 seconds.
Closed-circuit current measurement
If the vehicle battery is discharged for an unknown reason,
perform a closed-circuit current measurement as the first test.
For diagnostic purposes, it is important to not disconnect the
battery. Disconnecting the battery may reset a faulty control
unit, preventing proper diagnosis.
The following test is generally completed overnight using a
multimeterwith a closed circuitcurrent measurement adaptor
with a recording function
- Check that battery voltage is 12 volts or higher. If lower,
recharge battery.
- Switch off electrical consumers (interior lights, telephone,
aftermarket equipment, or others).
- Open luggage compartment and remove battery trim panel.
Use screwdriver to lock latch on trunk lid or hatch, simulating
closed luggage compartment. Close other doors.
- Open driver's door, then close it, simulating driver entering
vehicle.
- Switch ignition to RUN position for at least five seconds, then
turn ignition to OFF position. This simulates driving vehicle.
- Open and close driver's door, simulating driver leaving
vehicle.
- Lock car and arm alarm.
- Wait at least 16 minutes for consumer cut-off.