2001 BMW 525i 20 pin

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Fuel injectors, checking and replacing
The fuel injectors are electronically controlled solenoid valves
that provide precisely metered and atomized fuel into the en-
gine intake ports.
The injectors receive voltage from the ECM relay. The ECM
controls the opening by activating the ground circuit
forthe in-
jector valve solenoids. The ECM varies the duration (in milli-
seconds) of "opening" time to regulate the
airlfuel ratio.
For a quick
check of the injectors, run the engine and touch
each injector with a screwdriver or stethoscope. You should
feel a vibration or hear a buzzing
Remove fuel injection harness from injectors by unclipping
locking clip at each injector. Lift harness off injectors.
CA U JIOG
Be sure ignition is OFF before disconnecting or reconnecting
DME system components.
Use a multimeter to test injector coil resistance between in-
jector terminals.
l~uel injector coil resistance 16R at 20" C (68" F)
Disconnect negative
(-) battery cable
CAUTIOG
Prior to disconnecting the battery, read the battery discon-
nection cautionsgiven
in 001 General Warnings and Cau-
tions.
4 Remove plastic trim plugs (arrows) and fasteners, then re.
move cover from above fuel injectors.
- Disconnect vacuum line from fuel pressure regulator.
- Remove wiring harness duct mounting fasteners.

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Fuel Injection I
- As an alternative, harness connector housing can be sepa-
rated so that electrical
checlts can be made from backof con-
nector.
4 If replacing ECM, disconnect control module harness con-
nector (arrow) by releasing fastener and pivoting connector
up and
off ECM.
CAUTION-
Be sure ignition is OFF before disconnecting or reconnecting
DME system components.
- Remove ECM from retaining brackets and lift off holder.
- Installation is reverse of removal.
- Before attempting to start engine, use BMW service tester
DISplus, MoDiC, GTI or equivalent:
- Code replacement ECM with application information (i.e.
engine code, transmission type, etc.).
Align ECM to EWS (electronic immobilizer).
Siemens MS 41.1 ECM pin assignments
ECM pin assignments are given in Table b. For engine man-
agement system schematics, see ELE Electrical Wiring
Di-
agrams.
CAUTION-
a Always wait at least one minute after turning off the ignition
before removing the connector from the
ECM. If the con-
nector is removed before this time, residual power
in the
system relay may damage the
ECM.
Always connect or disconnect the control module con-
nector and meter probes with the ignition
off
When malting checks at the ECM itself, a breakout box
should be used to allow tests to be made with the connector
attached to the ECM. This also prevents damage to the small
terminals in the connector. As an alternative, the harness
connector housing can be separated so that electrical checlts
can be made from the back of the connector.
Table b. Siemens MS
41.1 ECM pin assignments
Pin
1
2
3
4
Signal
output
output
output
qround Componenfffunction
Ignition coil control, cyl. 2
Ignition coil control, cyl. 4
ignition coil control, cyl. 6
Ground Notes
Primary signal,
ignition
coil 2
Primary signal, ignition coil 4
Primary signal, ignition coil 6
Ground

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I Fuel Injection
Table b. Siemens MS 41.1 ECM pin assignments (continued)
Pin
l~iqnal I Componentlfunction 1 Notes I - I I
5 loutput I Fuel injector control, cyl. 2 I Pulsed ground (pulse width in ms), cyl. 2 I I I
6 loutput /Fuel injector control, cyi. 1 I Pulsed ground (pulse width in ms), cyl. 1
I I I
14 linput I Intake air temp. sensor (IAT) I Intake air temperature signal
- 7
8
9
10
11
12
13
ground
input
output
input
input
15
16
17 18
19
20
21
22
I - I I
35 loutput /Secondary air injection ISecondary air inj. pump relay control
25
26
27
28
29
30
31
32
33
36
/output I Engine speed output IEngine speed signal
Mass air flow sensor
Mass air flow sensor
instrument cluster
Engine coolant
temp.
(ECT) sensor
Not used
Throttle position sensor (TPS)
Not used
input
input
input
input
output
output
out~ut
37 1 - /Not used I
Mass air flow sensor signal
Mass air flow sensor signal
Fuel consumption signal
ECT signal
Throttle position signal
ground
input
output
ground
output
output
output
ground
output
Traction control (rear engine speed signal) Automatic climate control
Not used Electronic immobilizer control (EWS)
Auto. climate control
(AIC on input)
instrument
cluster
Camshaft actuator control (VANOS)
Fuel iniector control, cvl.
3
AES/ASC module
Automatic climate control instrument cluster (CARE signal)
Camshaft actuator (VANOS), switched ground
Pulsed ground (pulse width in
ms), cyl. 3
Oxygen sensor heater (no. 1 in front of catalytic
converter)
Power supply (terminal
30)
Idle speed control valve
Ground
Ignition coil control, cyl.
1
Ignition coil control, cyl. 3
Ignition coil control, cyl. 5
Ground Fuel injector control, cyl.
5
Oxygen sensor heater ground
Battery voltage
(E+) at all times
Pulsed ground-open signal (See pin
53)
Ground
Primary signal, ignition coil
1
Primary signal, ignition coil 3
Primary signal, ignition coil 5
Ground
Pulsed ground (pulse width in ms), cyl
5

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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

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/Fuel injection
Table b. Siemens MS 41.1 ECM pin assignments (continued)
85
86
87
88 CAN-Bus low
CAN-Bus high
Power supply
Diagnostic connector
(TxD)
inputloutput
inpuWoutput
input
input output Automatic transmission control module (AGS)
Automatic transmission control module (AGS)
Battery voltage from main relay terminal 87
Diagnostic TxD signal to pin 17 in data link connector

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- -.
Fuel Injection
SIEMENS MIS 42.0 AND 43.0
When system faults are detected, a diagnostic trouble code
(DTC) is stored in the engine control module (ECM). The MIL
also illuminates
if an emissions-related fault is detected.
When faults arise, or
if the malfunction indicator lamp (MIL) is
illuminated, begin troubleshooting by connecting BMW ser-
vice tester
DISplus, MoDiC, GTI or equivalent scan tool. The
capabilities of OBD
II software has the potential to save hours
of diagnostic time and to help avoid incorrect component re-
placement and possible damage to system components.
CAUTION-
* The tests in this section may set fault codes (DTCs) in tlie
ECM and illuminate the MIL. After all testing is completed,
access and clear DTC fault
memory using an OBD I/ or
BMW compatible scan tool. See
OBD On-Board Diag-
nostics.
Only use a
dgital multimeter for electrical tests.
Relay positions can vary. Be sure to confirm
relayposi-
tion by identifying the wiring in the socket using the wir-
ing diagrams found in
ELE Electrical Wiring
Diagrams.
NOTE-
- OBD I1 fault memory. (including an illuminated MIL! can
only be reset using the special 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
20-pin DLC is discontinued on models after
6/2000.
The 1 &pin OBD I1 diagnostic connector (arrow) is located
inside the car on the lower left dash panel.
The MS
42.0 and MS 43.0 systems manage the following
functions.
- Air:
Idle speed valve
Electronic throttle
Hot film mass air flow (MAF) sensor
Resonance-turbulence intake control
- Fuel:
* Fuel supply
Running losseslnon return
Fuel injection

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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 I
Working inside E-box, disconnect ECM harness connector
(arrow) by releasing fastener and pivoting connector up and
off ECM.
CA UTIOW
Be sure ignition is OFF before disconnecting or reconnecting
DME system components.
Remove ECM from retaining brackets and lift off holder.
Installation is reverse of removal
Before attempting to start engine, use
BMW service tester
DISplus, MoDiC, GTl or equivalent:
* Code replacement ECM with application information (i.e
engine code, transmission type, etc.).
Align ECM to EWS (electronic immobilizer).
Siemens MS 42.0 and MS 43.0
ECM pin assignments
ECM pin assignments are given in Table c. For engine man-
agement system schematics, see
ELE Electrical Wiring Di-
agrams.
/ CAUTIOW I
Al~ays wait at least one mfnule after turning off the ignition
before
remov;ng [he connecror irom rhe ECM. If the con-
nector is removed before this time, residual power
in the
system relay may damage the
ECM.
Always connect or disconnect the control module con-
nector and meter probes with the ignition off.
When making checks at the ECM itself, a
breakout box
should be used to allow tests to be made with the connector
attached to the ECM. This also prevents damage to the small
terminals in the connector. As an alternative, the harness
connector housing can be separated so that electrical checks
can be made from the back of the connector.
Table
c. Siemens MS 42.0 and MS 43.0 ECM pin assignments
Pin
lslgnal l~om~onentlfunction 1 Notes
Connector
X60001 9-pin black
1 loutput I~erminai 15 I Unloeder relay terminal 15
2 I 1 Not used I
3 Not used
4 Ground
Ground Ground
point