1998 BMW 540i check engine light

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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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ignition System
Crankshaft speed sensor, replacing (M62 and M62TU
engines)
The crankshaft speed sensor reads a toothed pulse wheel
mounted on the flywheel.
If the Engine Control Module(ECM)
does not receive an impulse signal from the crankshaft speed
sensor during
cranking, the engine will not start. If the OBD II
system misfire detection protocol detects a catalyst damag-
ing fault due to a malfunction in the crankshaft speed sensor
components, the Check Engine light (Malfunction
Indicator
Light or MIL) will be Illuminated.
4 The crankshaft speed sensor (arrow) is mounted in the right
lower side of the bell housing.
- Remove speed sensor by disconnecting electrical harness
connector and unbolting sensor from bell housing. Do not
discard shims, if present.
- Installation is the reverse of removal. Clean mounting surface
before installing new sensor, and install shims, if present.
< If the flywheel was replaced, the speed sensor must be
checked for correct installation depth.
* Crank engine in direction of rotation using crankshaft bolt
until a full pulse tooth is centered in the opening for the re-
moved speed sensor.
Measure depth ro top of tooth from speed sensor p~lse
generator mounting s~rface on transmission.
4 Measure length of pulse generator from mounting surface to
end (A).
- Subtract length of pulse generator (A) from distance to pulse
tooth from mounting area on transmission. This measure-
ment is the gap between the pulse sensor and flywheel. Use
shims available from BMW to increase gap as needed to
reach specification.
Pulse sensor
gap
End of sensor to flywheel teeth 0.55 + 0.2 rnrn
(0.0217 t 0.008 in)

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Battery, Starter, ~iternatorl
The battery is mounted in the right side of the luggage com-
partment, concealed behind a trim panel. Battery capacity is
determined by the amount of current needed to start the vehi-
cle and by the amount of current consumed by the electrical
system. This will vary from model to model.
BMW batteries are rated by
amperelhours (Ah) and cold
cranking amps (CCA) rating, which are listed on the battery.
The Ah rating is determined by the average amount of cur-
rent the battery can deliver over time without dropping below
a specified voltage. The CCA is determined by the battery's
ability to deliver starting current at
On F (-18" C) without drop-
ping below a specified voltage. Always replace the battery
with one having the same or higher ratings.
Battery testing
Battery testing determines the state of battery charge. On
conventional or low-maintenance batteries. the most com-
mon method of testing the battery is that
ofchecking the spe-
cific gravity of the electrolyte using a hydrometer. Before
testing the battery, check that the cables are tight and free of
- corrosion.
Hydrometer testing
Before hydrometertesting, load the battery with 15 amperes
for one minute. If the battery is installed in the vehicle, this can
be done by turning on the headlights without the engine run-
ning. The state of battery charge based on specific gravity
values are given in Table
b. Specific gravity of battery elec-
trolyte at
27" C (80°F).
The hydrometer indicates the specific gravity of the electro-
lyte. The more dense the concentration of sulfuric acid in the
electrolyte, the higher the state of charge
NOTE-
Electrolyte temperature affects hydrometer reading. Checlc
the electrolyte temperature with a thermometer. Add 0.004 to
the hydrometerreading
forevery 6°C (10°F) that the electro-
lyte is above 27°C
(80°F). Subtract 0.004 from the reading
forevery 6°C (10°F) that the electrolyte is below27"C
(80°F).

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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.

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121-8
/Battery, Starter, Alternator
NOTE-
Automatic transmission cars: ambershifier LED willgo out at
consumer cut-off.
4 Attach closed-circuit current measurement adaptor
(BMW special tool
61 2 300):
Connect red clamp (marked A -BATT (+)) to positive bat-
tery terminal.
Connect
black clamp (marked B -CHASSIS) to chassis
ground point.
NOTE-
Green LED will light up to indicate correct installation of
closed-circuit current measurement
adaotor.
< Connect blaclc clamp (marked B - BATT (-)) to negative bat-
tery terminal. Green
LED light will go out.
NOTE-
Any electrical overloading will be indicated at this point by
lighting the red
LED. If the red LED lights up, check the adap-
tor connections.
< Set multimeter (A) to 10 amp measuring range and connect
it to adaptor.
NOTE -
Set multimeter to record average readings.
Ifpossible, turn offpowersaving features of multimeter
which prevent a long term (overnight) test by automatically
powering down
meter.
- Disconnect battery ground strap (B) at chassis mounting
point.
- Measure closed-circuit current using multimeter.
- Typical average closed-circuit current for E39 vehicles is
40 mA. Readings over 50 mA must be further investigated.

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Battery, Starter, Alternator
Water-cooled alternator
The water-cooled alternator, used on 1999 and later M62 TU
engines, is a sealed unit housed inside the engine block wa-
ter jacket. It is cooled via the engine cooling system. It is a
"brushless" sealed unit that cannot be serviced. Maintaining
consistent alternator temperatures increases the life span of
the alternator, and elimination of the alternator cooling fan re-
duces alternator noise
significantly.
The M62 TU water-cooled alternator incorporates load start
reduction. This function is intended to shorten the duration of
engine starting, particularly at low ambienttemperatures. The
current load is limited to
20 amps during starting in order to re-
duce alternator braking torque on the engine. Following the
current limiting phase, full power output is then progressively
reached.
Charging system diagnostics requires special test equip-
ment. If the test equipment is not available, charging system
fault diagnosis can be performed by an authorized
BMW
dealer or other qualified repair shop. See Table a. Battery,
alternator and starter troubleshooting for general electri-
cal component troubleshooting.
Before checking the alternator, make sure the battery is fully
charged and capable of holding a charge. Check that the bat-
tery terminals are clean and tight and the alternator drive belt
is properly tensioned and not severely worn.
NOTE-
Some model require up to 15 second to reacli full alternator
output.
CA UTIOG
If the charge indicator light in the instrument cluster remains
on, the charge warning circuit in the instrument cluster may
be faulty. Check that the ground lead is securely
affached to
the grounding stud on the cylinder head
(A). Replacing the
instrument cluster before repairing the ground lead will both
damage the instrument cluster and cause the failure to
reoccur.

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Battery, Starter, ~lternatorl
Charging system quick-check
Use a digital multimeter to measure voltage across the bat-
tery terminals with key off and then again with engine running.
Battery voltage should be about 12.6 volts with key off and be-
tween 13.5 and 14.5 volts with engine running.
NOTE-
The regulated voltage (engine running) should be between
13.2 and 14.5, depending on temperature andoperating con-
ditions.
If the voltage is higher than 14.8, the voltage regula-
tor or
mulitfunction controller is most likely faulty
Check for clean and tight battery cables. Check ground cable
running from negative
(-) battery terminal to chassis and
ground cable running from engine to chassis. Check alterna-
tor drive belt condition and tension.
Charging system, checking
CAUTIOI\C
* Do not disconnect the battery while the engine is running.
Damage to the alternator and/or engine electronic systems
may result.
Only use a digital multimeter when testing charging
system components.
--7
4 Turn ignition key on. Check that battery warning light comes
on.
NOTE-
If the warning light does not come on, repair bulb or wiring
faults before continuing to checlc the charging system.
/ Charge indicator
502820805
4 6-cylinder engines only, remove complete air filter housing:
Loosen
intake duct hose clamp (A) at throttle assembly.
Loosen clamp and remove idle control hose from intake
duct
(B) and disconnect idle speed control valve electrical
harness connector.
Disconnect electrical harness connector
(C) from mass air
flow sensor.
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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- -
/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.