1998 BMW 540i Knock sensor

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j Cylinder Head Removal and Installation
4 Working at throttle housing, unscrew and disconnect electri-
cal harness plug
(arrow).
4 Disconnect electrical harness connector at fuel tank venting
valve
(A) and vent hose at quick disconnect fitting (arrow).
- Working under intake manifold, disconnect the following:
Engine oil dipstick tube support.
Oil separator return line from dipstick tube.
Knock sensor harness connector from support.
4 Working underneath car, remove intake manifold support
mounting nut
(arrow), located adjacent to left engine mount.

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.. Cylinder Head Removal and Installation I -
< Disconnect the following electrical harness connectors:
Knock sensors
(A).
Thermostat (6).
Throttle position sensor and idle valve (C).
Camshaft position sensor (D).
Ignition coils (E).
< Remove mounting nuts (arrows) from wiring harness ducts.
4 Release fuel injector connectors by releasing spring clip
(arrow) on each injector.
Lift up and remove electrical ducts and set to one side

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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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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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I Ignition System
Camshaft position sensors
The camshaft position sensors are used by the englne man-
agement system for VANOS control, sequential fuel injection
and knock control.
Intake camshaft position sensor, replacing
(M52,M52 TU
and M54 engines)
- Make certain ignition has been turned off.
- Remove plastic cover from above fuel injectors by prying off
bolt covers and removing cover mounting bolts.
Remove complete air filter housing:
Disconnect electrical harness connector on mass air flow
sensor
(A).
Detach vacuum line at intake boot (B).
Loosen hose clamp at intake boot and detach air duct con-
nections
(C).
* Disconnect cold air duct tube (D).
Remove filter housing mounting screws (E).
- Disconnect harness connector from VANOS solenoid and
unscrew solenoid from VANOS control unit. Be prepared with
shop rags to catch oil released from VANOS unit.
Remove camshaft sensor (arrow) from
left front of cyl~nder
head, next to top of oil filter housing.
Disconnect camshaft sensor harness from under intake
manifold. Prior to removal, attach a stiff piece of wire to the
harness connector end to preserve proper routing of harness
for reinstallation.
Installation is reverse of removal, noting the following:
Use new O-rings when installing sensor and solenoid.
Be sure wiring is rerouted in same orientation.
Use scan tool to read out and clear
ECM fault memory
Tightening torques
-
Intake camshaft sensor to cylinder head 10 Nrn (7 ft-lb)
VANOS solenoid to VANOS control unit 30 Nm (22 ft-lb)

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120-1 6
Ignition System
Remove camshaft sensor (arrow) from front of right cylinder
head.
Disconnect camshaft sensor harness from cable duct above
right cylinder head.
Installation is reverse of removal, noting the following:
Use new O-ring when installing sensor.
Be sure wiring is rerouted in same orientation.
Use scan tool to read out and clear ECM fault memory.
Tightening torque Intake camshaft sensor to timing chain 5 Nm
(3.5 ft-lb)
cover
Knock sensors
Knock sensors, replacing (M52, M52 TU and M54
engines)
The knock sensors are bolted to the left side of the cylinder
block under the intake manifold.
- Remove intalte manifold as described in 113 Cylinder Head
Removal and Installation.
D~sconnect knock sensor electrical harness connector (A) on
left side of engine cylinder block.
Remove knock sensor
mount~ng bolts (arrows) on side of
cyllnder block. Remove sensors.
Note the installed angle of the
lnocl~ sensor on the bloc/( be-
fore removing it. Reinstall the sensor
in the same position. Be
sure to use a torque wrench when tightening the sensor
mounting bolt.
< Clean lknock sensor contact surface on engine bloclc and
sensor (arrows) before installing
ltnock sensor.
Tightening torque
Knock sensor to head 20 Nm (15 ft-lb)
- Use scan tool to read out and clear ECM fault memory.
Knock sensors, replacing
(M62 and M62 TU engines)
The
knock sensors are bolted to the side of the cylinder block
under the
intake manifold.

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Ignition System
Remove intake manifold as described in 113 Cylinder Head
Remaval and Installation.
Remove knock sensor mounting bolts (arrows) on side of
cylinder block. Remove sensors.
I CAUTION- I
Note the installedangle of the knock sensors on the bloclt be-
fore removalit. Reinstall the sensors in the same position. Be
sure to use
a torque wrench when tightening the sensor
mounting bolts.
Clean
lknoclc sensor contact surfaces on engine bloclc and
sensors before installing.
Tightening torque
Knock sensor to engine
bloclc 20 Nm (15 ft-lb)
- Use scan tool to read out and clear ECM fault memory.
- Installation is reverse of removal.

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Fuel lniection 1
Table b. Siemens MS 41.1 ECM pin assignments (continued)
Pin
lSiqnal 1 Componentlfunction / Notes I - I I
40 1 ground /Crankshaft position sensor /crankshaft position sensor control I - I I
41 1 ground /Camshaft position sensor (CMP) /shielding for CMP sensor I - I I
42 1 ground I~hrottie position sensor (TPS) /TPS ground
43
44
45
46
47
48
49
50
51 ground
output
output
output
outout
I I I
input
52 53
54
55
56 57
58
59
60
61
62
63
64
65
66 Camshaft position sensor (CMP)
Throttle position sensor (TPS)
Throttle position sensor (traction control)
Instrument cluster
Not used
Crankshaft position sensor (Hall effect)
I~ot used
I I I
Fuel pump relay control Camshaft
positionlrpm sensor control
Voltage
supply to TPS (5 vdc)
ABSIASC module
Instrument cluster, fuel reserve signal
Crankshaft position sensor control
Power supply (terminal 15)
Not used
Not used
output input
ground
ground
output
input
output
inputloutput
ground
output
input
input
input
I I
Battery voltage with key on or engine running
Oxygen sensor signal ground
67
Idle speed control valve
Power supply
Oxygen sensor heater (no. 2 in front catalytic
converter)
Ignition circuit
Knock sensor
(cyl. 1-3)
Knock sensor (cyl. 1-3)
Knock sensor
(cyl4-6)
Data linic connector (TxD)
Oxygen sensor heater (no. 2 behind catalytic
converter)
Secondary air injection
Knock sensor (cyl. 4-6)
Camshaft
positionlrpm sensor
Camshaft
positionlrpm sensor
Not used
Pulse ground with engine at normal temperature with
varying engine load
68 Pulsed ground-close signal (see
pin 26)
Battery voltage from main relay (terminal 87)
Oxygen sensor heater ground
Ignition circuit monitoring signal
Knock sensor
Knock sensor signal
Knock sensor
Diagnostic
TxD (transmit) signal to pin 18 in data link
connector
Oxygen sensor heater ground
Secondary air injection control
valve
Knocic sensor signal
Camshaft positionlrpm sensor control
Camshaft
positionlrpm sensor control
ground Oxygen sensor
(no.
1 in front of catalytic
converter)
output Evaporative purge
valve control