2001 BMW 540i air flow sensor

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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.

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Fuel Injection
A faulty MAF sensor can produce the following problems:
Difficult to restart when engine is hot
Engine starts then stalls
* Engine starts and runs only with accelerator pedal de-
pressed
4 Disconnect electrical harness connector from MAF sensor
(B).
- Turn ignition on and checlc for voltage and ground at connec-
tor.
There should be ground at pin
1 and battery voltage at pin
3.
- If any faults are found, checlc for wiring breaks between
MAF sensor and ECM and between MAF sensor and main
DME relay.
NOTE-
Visually inspect the sensor for damage, missing or blocked
screens. The screens affect air flow calibration. Also inspect
the sealina
0-rinas where the sensor inserts into the air filter - - housing and intake boot. Ensure the pin connections are
clean and tight.
4 Connect a BMW-compatible scan tool or an OED II generic
scan tool.
Checlc air mass signal (load signal) with the engine
at idle. Raise idle speed and
checlc that load signal changes
with rpm.
CAUTION-
Be sure ignition is OFFbefore disconnecting or reconnecting
DME system components.
Remove MAF sensor:
Loosen intake boot clamp
(A).
Disconnect harness connector (6).
* Release clip from air filter housing (C) and remove sensor.
- Installation is reverse of removal.
No adjustment to MAF sensor is possible.
Check intake hoses for cracks and vacuum
lealts.

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Fuel Injection
4 Remove electrical harness connector (arrow) from IAT sen-
sor.
CAUTION-
Be sure the ignition switch is in the off position before repiac-
ins the intake temperature sensor.
- Depress loclting clip on side of temperature sensor and pull
straight out of intake manifold.
- Installation is reverse of removal
- Use a new sealing O-ring at base of sensor and lubricate with
assembly lubricant for
ease of installation
MS 42.0 throttle valve assembly, replacing
< The motor driven throttle valve for the MS 42.0 system is re-
- ferred to as MDK (motor driven throttle valve). The MDK unit
is electronically operated to regulate intake air flow by the
ECM.
The
MS 42.0 system uses a throttle cable from the accelera-
tor pedal to the MDK unit. The throttle cable is connected di-
rectly to the integral pedal position sensor
(PWG) in the MDK
unit. This sensor communicates pedal position to the ECM,
which in turn electronically regulates throttle plate position.
The MDK pulley is linked to the throttle shaft by springs to al-
low ASC intervention to override the driver's pedal position.
NO TE -
The MDIC unit is non-adjustable and must be replaced as
a complete unit if found to be faulty.
if replacing the
MDK unit, the adaptation values stored in
the ECM must be clearedand the new unit initialized using
BMW special service tools.
CAUTION-
If the adaptation process is not completed correct& the en-
gine wiii
not start.
- Disconnect battery negative (-) cable in luggage compart-
ment.
CAUTION-
Prior to disconnecting the battern read the battely discon-
nection cautions in
001 General Warnings and Cautions.

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Fuel lniection I
4 Remove complete air filter housing:
Disconnect electrical harness connector on mass air flow
sensor
(A).
Disconnect vacuum line at intake boot (B).
Loosen Intake air duct clamp (C).
Remove filter housing mounting screws
Disconnect air duct and
lift complete air filter housing and
MAF sensor out of engine compartment, pulling it forward
away from throttle housing.
- Pull throttle cable upwards out of rubber retainer and unhoolc
ball end of cable from throttle actuator.
4 Remove nuts and bolts (arrows) retaining wiring harness to
throttle housing.
- Working at throttle housing, turn harness plug counterclock-
wise and remove plug.
4 Working at side of intake manifold, disconnect electrical har-
ness connectors:
Idle control valve (A)
lntalce manifold resonance valve (B)
- Disconnect electrical harness connectors at oil pressure
sender and oil temperature sender at base of oil filter hous-
ing.
CO,l,> ti,, "F"bl,rl,irrm.,-AI ",",>ti

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Fuel Injection
MS 43.0 throttle valve assembly, replacing
The electronic throttle valve assembly forthe MS43.0 system
is referred to as
EDK (electronic throttle valve). There is no
mechanical (cable) link between the accelerator pedal and
the throttle plate.
< The accelerator pedal module (PWG) at the pedal assembly
communicates the pedal position directly to the ECM. The
module provides two variable voltage signals (via two Hail
sensors) to the ECM for pedal position and rate of movement.
NOTE-
The EDK unit is non-adjustable and must be replaced as a
complete unit if found to be faulty
If replacing the
EDK unit, the adaptation values stored in
the
ECM must be cleared and the new unit initialized using
BMW special service tools.
CAUTIOIG
If the adaptation process is not completed correctk the en-
qine will not start
- Disconnect battery negative (-) cable in luggage compart-
ment.
CAUTION-
Prior to disconnecting the battery, read the battery discon-
nection cautions given in
001 General Warnings and Cau-
tions.
< Remove complete air filter housing:
- Disconnect electrical harness connector on mass air flow
sensor
(A).
Disconnect vacuum line at intake boot (6).
Loosen intaite air duct clamp (C).
Remove filter housing mounting screws.
Disconnect air duct and lift complete air filter housing and
MAF sensor out of engine compartment, pulling it forward
away from throttle housing.

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.-
/Fuel Injection
I ' I - I
9 /ln~ut l~oltaqe supply I Fuse carrier, engine electronics
Table
c. Siemens MS 42.0 and MS 43.0 ECM pin assignments (continued) I ' I . I
Connector X60002 24-pin
1 linput IHeater, precatalyst oxygen sensor 1 I Heated oxygen sensor 1 in front of cat. conv.
I I I
18 llnout IHeater, post-catalyst oxygen sensor 2 ]Heated oxygen sensor 2 behind cat. conv.
Notes
Ground connector
Ground connector
B+ terminal
Fuse carrier, engine electronics
Pin
5
6
7
8
I I I
4 loutput l~hrottle valve supply (MS
42.0) I~hrottle valve (MS 42)
Signal
Ground
Ground Input
lnout
19
20 21
22
23
24
Connector
1
2
3
I I I
5 1 lnput ISignal, intake camshaft position sensor /camshaft position sensor 1
Componentlfunction
Ground
Ground
Terminal 30
Voltaae
SUDP~V
input
Ground
Ground
Ground
Input
Ground
X60003 52-pin
Input
Input
~ -
Heater, post-catalyst oxygen sensor 2
Ground, precatalyst oxygen sensor
1
Ground, precatalyst oxygen sensor 2
Ground, post catalyst oxygen sensor
1
ECM (DME main) relay signal activation
Ground, post catalyst oxygen sensor 2
Signal, mass air
flow sensor
Signal, exhaust camshaft sensor
Not used Heated
oxygen sensor 2 behind cat.
conv.
Heated oxygen sensor 1 in front of cat. conv.
Heated oxygen sensor 2 in front of cat. conv.
Heated oxygen sensor
1 behind cat. conv.
ECM
Heated oxygen sensor 2 behind cat. conv.
Hot film mass air flow sensor
Camshaft position sensor

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130-43
Fuel Injection ]
I I I
12 llnput IFeedback signal, engine start /Starter
Table c. Siemens MS 42.0 and MS 43.0 ECM pin assignments (continued)
I I - I
13 Input /I Alternator (generator) Notes
Throttle
valve
Crankshaft position sensor
Throttle valve (MS
42.0)
Throttle valve
Pin
6
7
8
9
10
11
14
15
16
17
18
19
20
I 1- I
23 l~round I~round, intaite air temperature sensor /Intake air temperature sensor
Signal
Output
Input
Input
Input
I I I
Component/function
Not used
Throttle valve supply potentiometer
2
Signal, crankshaft position sensor
Signal,
pedal position sensor 2 (MS 42.0)
Signal, throttle position sensor 1
Not used
Ground
Ground
Input
Ground
Ground
Input
Ground Cranltshaft position sensor
21
24
25
26
27
28
29
30
I 1- I
33 1 input ISignal, cylinder 1 fuel injector /cylinder 1 fuel injector
Ground, throttle position sensor (MS
42.0)
Ground, exhaust camshaftsensor I
Signal, pedal position sensor 1 (MS 42.0)
Ground, mass air flow sensor
Ground, intake camshaft sensor
1
Signal, throttle potentiometer 1
Ground, throttle position sensor
22 loutput I~ignal, intake air temperature Ilntake air temperature sensor
I I - I
Throttle
valve (MS 42.0)
Camshaft position sensor I
Throttle valve (MS
42.0)
Hot film mass air flow sensor
Camshaft position sensor i
Throttle valve
Throttle valve
Ground
Output
Ground Input
Output
Ground
Output
Out~ut
Ground, crankshaft position sensor
Knoclt sensor
31
34
35
36
37
38
39
Signal, coolant temperature sensor
Ground, coolant temperature sensor
Signal,
oil pressure
Signal, engine
oil temperature sensor
Ground, engine oil temperature sensor
Signal, knock sensor
Signal, knock sensor
32 loutput ISignal, ltnock sensor l~nock sensor
40
41
Coolant temperature sensor
Coolant temperature sensor
Oil pressure switch
Oil temperature sensor
Oil temperature sensor
Knoclt sensor
I Output
Input
input
Input
Input
Input
Inout
Signal, knock sensor
Input
Input Signal, cylinder
2 fuel injector
Signal, cylinder
3 fuel injector
Signal, cylinder
4 fuel injector
Signal, cylinder
5 fuel injector
Signal, cylinder
6 fuel injector
Sianai, oil level sensor Cylinder
2 fuel
injector
Cylinder
3 fuel injector
Cylinder
4 fuel injector
Cylinder
5 fuel injector
Cylinder
6 fuel injector
Oil level sensor
-
Signal. VANOS inlet valve
Signal. VANOS outlet valve VANOS
inlet valve
VANOS outlet valve

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- Fuel Injection
ECM relay, testing
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.
CAUTIOI\C
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.
ECM relay powers:
* ECM
Ignition coils
Fuel injection
Evaporative leak detection pump
(5.2.1 only)
Idle air actuator
Camshaft sensors Evaporative emissions valve
Hot film mass air flow sensor
Fuel pump relay
Oxygen sensor heaters
4 Working in right rear of engine compartment:
Release interior ventilation filter cover latch
(A) and re-
move cover.
Release plastic locking tab
(B).
Rotate duct inward (arrow) to unloclc from bulk head and
remove duct.
0 Release spring lock (C) to remove lower filter housing.
Slide filter housing away from inner fender to remove.
- Remove electrical box (E-box) cover fasteners and remove
cover.