1994 BMW 325i Mass air flow sensor

5
.
Remove
air
filter
housingcomplete
with
mass
air
flow
sensor
.
See113
Cylinder
HeadRemoval
and
Instal-
lation
.

6
.
Remove
oil
dipstick
guide
tube
mounting
bolt
.
Discon-
nect
oil
separator
hose
frombase
of
guide
tube
and
re-
move
tubefrom
oil
pan
(where
applicable)
.
See
Fig
.
10
.

NOTE-

The
guide
tube
is
sealed
in
the
blockusing
an
O-ring
.
Check
that
the
O-ring
comes
out
with
the
tube
.
Use
a
new
O-ring
when
installing
the
tube
.

Fig
.
10
.
Oil
dipstick
guide
tube
being
removed
.
Use
new
O-ring
(ar-
row)
during
installation
.

7
.
M50/S50US
engine
:
Using
a
clean
syringe,
remove
power
steering
fluid
from
fluid
reservoir
.
Disconnect
power
steering
fluid
lines
from
steering
rack
.
See
320
Steering
and
Wheel
Alignment
.

8
.
M52/S52US
engine
:
Unbolt
power
steering
reservoir
from
engíne,
then
tie
to
chassis
with
wire
.

9
.
Insta¡¡
engine
lifting
equipment
atfront
engine
lifting
point
and
raise
engine
approximately
5
mm
('/a
inch)
until
engineweight
is
supported
.
See
Fig
.
11
.

10
.
Workingbeneath
car,
separate
steering
column
shaft
from
steeringrack
at
universal
joint
.

"
Mark
steering
column
shaft
jointto
steering
rack
spin-

dle
.
Point
wheels
straight
ahead
before
disconnecting
shaft
from
rack
.
See
320
Steering
and
Wheel
Align-
ment
.

LUBRICATION
SYSTEM



119

Fig
.
11
.
Engine
lifting
equipment
shown
installed
acrossengíne
.

CA
UTION-

In
order
to
avoid
the
need
for
front-end
realign-
ment,
donot
unbolt
power
steering
rack
from
sus-
pension
crossmember
.

11
.
Support
suspension
crossmember
from
below
using
appropriate
jacking
equipment
.

12
.
Loosen
nuts
at
top
of
left
and
right
side
engine
mounts
.
Remove
nuts
from
bottom
of
left
and
right
side
engine
mounts
.

13
.
At
left
and
right
sides,
unbolt
control
arm
bushíng
carri-
ers
from
body
.
Disconnect
stabilizer
bar
links
fromcon-
trol
arms
.
Refer
to
Fig
.
3
.

14
.
Remove
bolts
from
left
and
right
sides
of
suspension
crossmember
and
lower
front
axle
as
far
as
possible
.

15
.
Remove
fuelline
clamping
brackets
from
oil
pan
.
On
cars
with
automatic
transmission,
remove
ATF
cooler
line
brackets
from
oil
pan
.

16
.
Remove
oil
pan
screws
.
Lower
and
remove
oil
pan
for-
ward
to
remove
.

CA
UTION-

If
the
oil
pan
does
not
separate
easily
from
the
en-
gine
cylinder
block,
a
few
taps
with
a
rubber
mallet
shouldbreak
it
free
.
Do
notpry
the
oil
pan
loose
.

OIL
PAN

2
.
Remove
cooling
duct
or
terminal
cover
from
rear
of
al-



2
.
Remove
air
cleaner
upper
section
with
mass
air
flow
ternator
.



sensor
.

3
.
Check
for
battery
voltage
between
ground
and
terminal



3
.
Remove
terminal
cover
from
rear
of
alternator
.
Discon
B+
at
back
of
alternator
.
Then
turn
ignition
on
and



nect
wiring
.
check
for
battery
voltage
between
terminal
D+
and
ground
.
See
Fig
.
3
.
lf
voltage
is
not
present
at
either



4
.
Remove
drive
belt
from
alternator
pulley
.
See
020
point,
check
wiring
for
faults
.



Maintenance
program
.

001
¡987
Fig
.
3
.



Terminal
B+
is
supplied
battery
voltage
directly
from
the
bat-
tery
.
Terminal
D+
is
supplied
battery
voltage
via
the
charge
warning
bulb
when
thekey
is
on
or
the
engine
is
running
.

4
.
lf
no
faults
are
foundup
to
thispoint,test
alternator
out-

put
using
a
load
tester
.

5
.
If
a
load
tester
is
not
available,
a
crude
output
test
can
be
done
by
running
engine
at
about
2000
rpmand
turn-
ing
on
electrical
loads
(fans,
lights
and
rear
window
de-
froster,
wipers)
.
With
al¡
accessories
on,
battery
voltage
should
be
above
12
.0
VDC
.

A
replacement
alternator
should
have
the
same
rating
as
the
original
.
Alternator
manufacturer
and
ampere
rating
are
normally
marked
on
the
alternator
housing
.
1
.
Disconnect
negative
(-)
battery
cable
.

CAUTION-

Prior
to
disconnecting
the
battery,
read
the
battery
disconnection
cautions
given
at
the
front
of
this
manual
on
page
vi¡¡
.

BATTERY,
STARTER,
ALTERNATOR



121-
5

6
.
Remove
upper
and
lower
mounting
bolts
and
lift
out
al-
ternator
.
See
Fig
.
4
.

NOTE
-

If
reusing
drive
belt,
mark
direction
of
rotation
on
belt
before
removing
.

5
.
On
M44
engine
with
hydraulic
belt
tensioner
:
Remove
tensioner
idler
pulley
(upper
roller)
from
alternator

bracket
.

Fig
.
4
.



Alternator
mounting
bolts
(arrows)
.

O



u
J
S
v~~

U

I



1
i
n
-12
.22

Alternator,
removing
and
installing



7
.
Installation
is
reverse
of
removal
.
Install
drive
belt
as

(4-cylinder
engine)



described
in
020
Maintenance
Program
.

Tightening
Torques

"
D+
vire
to
alternator
(M6
nut)
.
...
.
.
.
7
Nm
(53
in-lb)

"
B+
wire
to
alternator
(M8
nut)
..
.
.
.
.
.
13
Nm
(10
ft-Ib)

"
Pulley
to
alternator
(M16
nut)
...
..
..
60
Nm
(44
ft-Ib)

ALTERNATOR
SERVICE

GENERAL
.
.
.
.
.
.
.
.
.
...
.
.
.
.
.
.
.
.........
130-2



Intake
air
temperature
(IAT)
sensor,

Principles
of
Operatinn
.
.
.
.
.
.
.
.
.
.........
130-2



testing
and
replacing
...
.
...
.
.
.
.......
.
130-19

Basic
Engine
Settings
.
.
.
.
.
.
.
.
.
.
.
.
.
.
...
:
.
130-3



Throttle
position
sensor
(TPS),

DISA
(Dual
Resonance
Intake
System)
.
.
.
.
.
130-3



testing
and
replacing
...
.
...
.
.
.
.
.
...
.
.
.130-19

On-Board
Diagnostics
(OBD)



Idle
speed
control
valve,
testing
.
.
.
.
.
.
.
.
.
.
130-20

and
Fault
Diagnosis
.
.
....
.
......
.
.
.
...
130-4



Idle
speed
control
valve,
replacing
.
.
.
.
.
.
..
130-21

SecondaryAir
Injection
.
.
.....
.
.........
.
130-5



BOSCH
DME
M5
.2
COMPONENT
Warnings
and
Cautions
.
.
...
.
.
.
.........
.
130-6



REPLACEMENT
.....
.
......
.
....
.
.
.
..
130-21

ELECTRICAL
CHECKSAND



Mass
air
flow
sensor,
replacing
.
.
....
.
....
130-22

COMPONENT
TESTING
.
.
.
.
.
.
.
.
...
.
.
.
.
.
130-7



Engine
coolant
temperature
(ECT)

Main



sensor,
replacing
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
130-22
rela
y
testing



130
-7
,...
.
.
.
.
.
.
.
.
.
...
.
.
.
.
.
.
.



Intake
air
temperature
(IAT)
sensor,
Fuel
pump
relay,
testing
.
.
.
.
.
.
.
...
.
.
.
.
.
.
.
130-7



rep
lacin
.
.
.
.
.
.
.
.
.
.
.g



.
.
.
.
.
.
.
...
.
.
.
..
.130-22
Oxygen
sensor,
testing
(Boschsystems
only)
130-8



Throttle
poson
sensor
(TPS)
replacing



13022
,



..
.-

FUEL
DELIVERY
TESTS
...
.
....
.
.
.
...
.
130-9



Idle
speed
control
valve,
replacing
...
.
....
.130-23

Operating
fuel
pump
for
tests
.
.
.......
.
...
130-9



SIEMENS
MS
41
.1
COMPONENT
Relieving
fuel
pressure
and



REPLACEMENT
.
...
.
.
.
.
.
.......
.
....
.130-23
connecting
fuel
pressure
gauge
......
.
..
130-10

Residual
fuel
pressure,
testing
.
.....
.
.
.
.
.
130-10



Mass
air
flow
sensor,
replacing
.
.......
.
.
.130-25

Fuel
pressure
regulator
response



Engine
coolant
temperature
(ECT)

to
engine
load,
testing
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
130-11



sensor,
replacing
.....
.
.
.
.
.
.........
.130-25

Fuel
rail
and
injectors,
checking
...
.
.
.
.
.
.
.
130-11



Intake
air
temperature
(IAT)
sensor,
replacing
.
.
.
.
.
.....
.
.
.
.
.
.
.
.......
.
.
.130-25
Fuel
rail
and
injectors,
replacing



..
.
.
.
.
.
.
.
130-12



Throttleposition
sensor
(TPS),
replacing
.
.
.
130-26
Fuel
PressureRegulator
.........
.
.
.
.
.
.
.
130-13



Idle
s
eed
control
valve,
re
lacin



130-26
Fuel
pressure
regulatorreplacing



p



p



g
.'''...
.
'
,

(fuel
rail
mount)
...
.
.
.
.
.
.............
130-13



ECM
PIN
ASSIGNMENTS
.............
.
.
130-26
Fuel
pressure
regulator,
replacing



Engine
control
module
(ECM),
accessing
...
130-26
(undercar
mount)
.
.
.
.
.
.
.
.
.........
.
.
130-14

BOSCH
DME
M1
.7
COMPONENT

TESTS
AND
REPAIRS
.
.
.
.
.
...
.
.
.
.
.
.
.
.
130-14

Air
flow
sensor,
testing
and
replacing
.
.
.
.
.
.
130-14

Engine
coolant
temperature
(ECT)

sensor,
testing
and
replacing
...
.
.
.
.
.
.
.
.
130-15

Throttle
position
sensor
(TPS),

testing
and
replacing
.
..........
.
.....
130-16

Idle
speed
control
valve,
testing
and
replacing
.
.
.
.
.
............
130-16

BOSCH
DME
M3
.1
AND
M33
.1

COMPONENT
TESTS
AND
REPAIRS
.
.
.
130-17

Mass
Air
Flow
Sensor
.
.
.
.
.
.
.
.
.....
.
.
.
.
.130-17

Mass
air
flow
sensor
(hotwire),testing
and
replacing
.
.
.
.
.
.....
.
.
.
.
.
.
.
130-17

Mass
air
flow
sensor
(hot
film),

testíng
and
replacing
.
.
.
.....
.
.
.
.
.
.
.
.
.
130-18
Engine
coolant
temperature
(ECT)

sensor,
testing
and
replacing
..
.
.
.
.
.
...
.
130-18

130
Fuel
i
n
jection

FUEL
INJECTION



130-1

TABLES
a
.
Engine
Management
System
Variants
.........
.130-2
b
.
Mass
Air
Flow
Sensor
Variants
..
.
..
..........
.130-2
c
.
Fuel
Pressure
Specifications
..
.
.
...
..........
130-11
d
.
Engine
Coolant
Temperature
Sensor
or
Intake
Air
Temperature
Sensor
Test
Values
(DME
1
.7)
...
.
130-15
e
.
ThrottlePosition
Sensor
Tests
(DME
1
.7)
......
.130-16
f
.



Engine
Coolant
Temperature
Sensor
or
Intake
Air

Temperature
Sensor
Test
Values
(DME
3
.1/3
.3
.1)130-19
g
.
Throttle
Position
Sensor
Tests
(DME
3
.1/3.3
.1)
.
.130-20
h
.
ECM
Pin
Assignment-Bosch
DME
M1
.7
....
.
..
.130-28
i.



ECM
Pin
Assignment-Bosch
DME
M3
.1
.......
.130-30
j
.



ECM
Pin
Assignment-Bosch
DME
M3
.3
.1
.....
.130-32
k
.
ECM
Pin
Assignment-Bosch
DME
M5
.2
.......
.
130-34
I.



ECM
Pin
Assignment-Siemens
DME
MS
41
.1
..
.
130-36

130-2



FUEL
INJECTION

GENERAL

This
repair
group
covers
fuel
injection
system
component

testing
and
repair
.
Special
equipment
is
necessary
for
some

of
the
procedures
given
in
this
repair
group
.
If
you
do
not
have

the
equipment
required
to
do
the
job,
it
is
recommended
that

these
repairs
be
left
to
an
authorized
BMW
dealer
.
The
BMW

dealer
is
equipped
with
sophisticated
diagnostic
test
equip-

ment
that
is
capable
of
quicklypinpointing
hard-to-find
fuel
in-

jection
problems
.

NOTE-

"
Wiring
diagrams
for
the
engine
management
system,

can
be
found
at
the
rear
of
the
manual
under
Electri-
cal
Wiring
Diagrams
.

"
For
ignition
system
repairinformation,
see120
Igni-

tion
System
.

"
For
fuel
supply
system
testing
and
repair,
see160



The
engine
control
module
(ECM)
uses
electrical
signals

Fuel
Tank
and
Fuel
Pump
.



from
the
mass
air
flow
sensor,
the
air
and
coolant
temperature

sensors,
the
crankshaft
position/rpm
sensor,
the
knock
sen

Principies
Of
Operation



sors
and
the
oxygen
sensorsas
the
primary
inputs
to
electron-

ically
control
fuel
delivery
and
ignition
timing
.

There
are
five
versions
of
engine
management
systems

usedon
the
E36
cars
.
Each
has
the
same
basic
components

and
operating
principles
.
The
most
notable
difference
is
that

1996
and
later
cars
use
a
sophisticated
OBD
II-compliant
sys-

tem
.
See
Table
a
.

Table
a
.
Engine
Management
System
Variants

Engine
code/year



1
System

4-cy1inder
M42
(1
.8
I)
1992-1995



Bosch
DME
Ml
.7
M44
(1
.91)
1996-1998



~
Bosch
DME
M5
.2
(OBD
II)

6-cylinder
M50
1992
(2.5
I)



Bosch
DME
M3
.1
1993-1995
(2.5
I)



Bosch
DME
M3
.3.1
(VANOS)
M52
1996-1998
(3281-
2
.8
I)



Siemens
MS
41
.1
(OBD
II)
1998
(3231
-
2
.5
I)



Siemens
MS
41
.1
(OBD
II)
M-Power
S50US
(M3
-
3
.01)
1995



Bosch
DME
M3
.3
.1
S52US
(M3
-
3
.21)
1997-1998



Siemens
MS
41
.1
(0131)
11)

NOTE-

-
Descriptions
and
procedures
in
the
first
partof
this
re-

pairgroup
refer
to
all
the
various
engine
management
systems
.

"
Particulars
of
each
fuel
injection
system
are
treated
in
separate
sections
in
the
second
part
of
this
repair
group
.

GENERAL

Fig
.1
.



OBD
II
diagnostic
connector
locatíon
.

The
fuel
injection
system
is
completely
electronic
in
opera-

tion
.
Air
flow
is
measured
electronically
via
a
mass
air
flow

sensor
and
additional
sensors
supply
information
about
en-

gine
operating
conditions
.
The
ECM
calculates
the
amount
of
fuel
needed
for
the
correct
air-fuel
ratio
and
actuates
the
fuel

injectors
accordingly
.
The
amount
offuel
metered
to
theen-

gine
is
determined
by
how
long
the
injectors
are
open
.

Airintake
.
Air
entering
the
engine
passes
through
a
pleat-

ed
paper
air
filter
in
the
air
cleaner
.
Intake
air
volume
or
mass

is
then
measured
bya
mass
air
flow
(MAF)
sensor
.
In
al¡
ex-

cept
the
vane
type
sensor
(DME
M1
.7),
a
reference
current
is

used
to
heat
a
thin
wireor
film
in
the
sensor
when
the
engine

is
running
.
The
current
used
to
heat
the
wire/film
is
electroni-

cally
converted
into
a
voltage
measurement
corresponding
to

the
mass
of
the
intake
air
.

Table
b
.
Mass
Air
Flow
Sensor
Variants

System



Al
r
flow
sensor
type

Bosch
DME
M1
.7



Vane
(volume
sensor)

Bosch
DME
M3
.1



Hot
wire
(mass
sensor)

Bosch
DME
M3
.3
.1



Hot
film
(mass
sensor)

Bosch
DME
M5
.2



Hot
film
(mass
sensor)

Siemens
MS
41
.1



Hot
film
(mass
sensor)

"
The
16-pin
OBD
11
diagnostic
connector
is
located
on



NOTE-

the
lower
left
dashpanel
.
See
Fig
.
1
.



On
cars
equipped
wíth
tractioncontrol,
an
additional
throttle
valve
is
controlled
by
an
electronic
throttle
actu-
ator
(motor)
.
This
valve
is
used
for
engine
speed
inter
vention
.
Repair
information
forthis
system
is
notcovered
here
due
to
the
special
electrical
testing
equip-
ment
required
to
service
it
.

BOSCH
DME
MM
AND
M33
.1

COMPONENT
TESTS
AND
REPAIRS

Consult
Table
a
for
engine
application
information
for
the

Bosch
DME
3
.1
and
3
.3.1
systems
.

The
DME
3
.1
and
DME
3
.3
.1
systems
are
similar
in
opera-

tion,
with
knock
control
and
VANOS
operation
being
the
key

differences
.
DME
3
.1
engines
arenot
equipped
with
VANOS

or
knock
detectors,
while
the
DM
E3
.3
.1
system
is
.

CA
UTION-

Use
onty
a
digital
multimeter
when
testing
wiring
.
Use
of
an
analog
VOM
may
damage
the
engine
control
module
.

Fig
.
25
.
Mass
air
flow
sensor
.
Hot
wire
sensor
usedon
carswith
DME
Electrical
tests
of
the
main
and
fuel
pump
relays
and
the



3
.1
(1992
6-cylinder
models)
.

DME
engine
control
module
(ECM)
are
covered
earlier
in
this

section
.
Fuel
pump
tests
are
covered
in
160
Fuel
Tank
and



CAUTION-
Fuel
Pump
.
Use
only
a
digital
multimeter
when
checking
the
mass
air
flow
sensor
.
An
analog
meter
can
dam-
Mass
Air
Flow
Sensor



age
theair
flow
sensor
.

There
are
two
types
of
mass
air
flow
sensors
used
onthe



1
.
Disconnect
air
flow
sensor
from
air
cleaner
only
.
Leave

cars
covered
by
this
section
.
Testing
procedures
vary
de-



it
connected
to
duct
leading
to
intake
manifold
and

pending
on
type
installed
.
The
airflow
sensor
is
not
adjustable



leave
wiring
harness
connected
.

and
must
only
be
tested
with
a
digital
multimeter
.

Mass
Air
FlowSensor
Variants

"
1992
M50
engine

DME
M3
.1
.
.
.
.
...
..
mass
air
flow
sensor-hot
wire

"
1993-1995
M50
and
S50US

DMEM33
.1)
.
...
...
.
mass
air
flow
sensor-hot
film

Mass
air
flow
sensor
(hot
wire),

testing
and
replacing

When
the
engine
is
running,
a
current
is
used
to
heat
a
thin

wire
in
the
center
of
the
sensor
.
See
Fig
.
25
.
The
current
in
the

wire
is
regulated
to
maintain
a
temperature
of
100°C
more

than
the
air
passing
over
it
.
The
current
used
to
heat
the
wire

is
electronically
conneced
into
a
voltage
measurement
corre-

sponding
to
the
mass
of
intake
a¡
r
.

To
keep
the
wire
clean,
it
is
heated
to
a
temperature
of
about

1,000°C
(1,830°F)
for
one
second
.
This
"burn-off"
cycle
takes

place
automatically,
four
seconds
after
the
engine
is
tumed
off
.

lf
thehot
wire
breaks
or
if
there
is
no
output
from
the
air
flow

sensor,
the
ECM
automatically
switches
to
a
"limp-home"

mode
and
tucos
on
the
Check
Engine
light
.
The
engine
can

usually
be
started
and
driven
.
The
air
flow
sensor
has
no
inter-

nal
moving
parts
and
cannot
be
serviced
.

FUEL
INJECTION



130-
1
7

2
.
Start
engine
and
run
it
to
normal
operating
temperature
.

3
.
Rev
engine
toat
least
2,500
rpm,then
shut
it
off
.
Look

through
meter
at
hot
wire
.
After
approximately
four
sec-

onds
wire
should
glow
brightly
for
about
one
second
.

NOTE
-

If
the
wire
glowsas
specified,
then
the
airflow
meter
and
ECM
are
probably
operating
correctly
.
lf
the
wire
does
not
glow,
continue
testing
.

4
.
lf
the
wire
does
not
glow,
remove
air
flow
sensor
and

look
through
it
to
see
if
wire
is
broken
.
lf
wire
is
broken,

meter
will
have
to
be
replaced
.

5
.
Reinstall
air
flow
sensor
and
harness
connector
.
Peel

back
rubber
bootfrom
harness
connector
.
Working

from
rear
of
connector,
connect
digital
voltmeter
across

terminals
1
and
4
.
See
Fig
.
26
.

6
.
Start
and
rev
engine
toat
least
2,500
rpm,thenshut
it

off
.
After
about
4
seconds,
voltage
should
riseto
about

4
volts
for
about
one
second
.
lf
voltage
is
present,
but

wire
does
not
glow,
air
flow
sensor
is
faulty
and
should

be
replaced
.

7
.
lf
voltage
is
not
present
in
step
6,
turn
ignition
key
on

and
check
for
voltage
and
ground
at
sensor
.
There

should
beground
at
pin
4
.
There
should
be
positive
(+)

battery
voltage
at
pin
2
.

BOSCH
DME
M3
.1
AND
M32
.1
COMPONENT
TESTS
AND
REPAIRS

130-18



FUEL
INJECTION
The
engine
coolant
temperature
(ECT)
sensor
sends
con-

tinuous
engine
coolant
temperature
information
to
the
ECM
.
Fig
.
26
.
Mass
air
flow
sensor
terminalidentifcation
on
carswith
DME



As
temperature
increases
sensor
resistance
decreases
.
M3
.1
fuel
injection
.

Mass
air
flow
sensor
(hot
film),

testing
and
replacing

MOTE-

A
burn-off
cycle
is
not
used
on
hot
film
sensors
.

8
.
With
ignition
off,
disconnect
harness
connector
from
air



ECT
Sensor
Location
flow
sensor
.
Using
a
digital
multimeter,
check
resis-



"
M50/S50US
engine
............
left
side
of
cylinder
tance
at
terminals
listed
.



head
under
intake
manifold

Air
Flow
Sensor
Test
Values
(DMEM3
.1)

"
Terminals
5
and
6
.
.
.
.........
..
.
..
....
3-4
ohms

If
any
faults
are
found,
check
wiring
lo
and
from
the
ECM
.
Make
ECM
pinout
test
as
listed
in
See
Table
i
.
Main
power
to
air
flow
sensor
comes
from
DME
main
relay
.

On
cars
with
DME
M3
.3
.1
a
hot
film
mass
air
flow
sensor
is
used
.
When
the
engine
is
running,
a
current
is
used
lo
heat
a
thinfilm
in
the
center
of
the
sensor
.
This
current
is
electroni-
cally
converted
into
a
voltage
measurement
corresponding
to
the
mass
of
intake
air
.

If
thehot
film
breaks
or
if
there
is
no
output
from
the
air
flow
sensor,
the
ECM
automatically
switches
to
a
"limp-home"
mode
and
tucos
on
the
Check
Engine
light
.
The
engine
can
usually
be
started
and
driven
.
The
air
flow
sensor
has
no
inter-
nal
moving
parts
and
cannot
be
senricedor
adjusted
.

CA
UTION-

Use
only
a
digital
multimeter
when
checking
the
mass
air
flow
sensor
.
An
analogmetercan
dam-
age
the
air
flow
sensor
.

BOSCH
DME
M3
.
1
AND
M32
.1
COMPONENT
TESTS
AND
REPAIRS

1
.
Disconnect
harnessconnector
from
air
flow
sensor
.

2
.
Turn
ignition
on
and
check
for
voltage
and
ground
at

connector
.
There
should
beground
at
pin
1
.
There

should
be
positive
(+)
battery
voltage
at
pin
3
.
If
any
faults
are
found,
check
wiring
to
and
from
ECM
.
Make
ECM
pinout
test
.
See
Table
j
.

NOTE-

Positive
(+)
battery
voltage
to
air
flow
sensor
comes
from
DME
main
relay
when
the
ignition
is
switch
on
orengine
running
.

Engine
coolant
temperature
(ECT)
sensor,

testing
and
replacing

0012704
Fig
.
27
.
Engine
coolant
temperature
(ECT)
sensor
(A)
is
located
be-
neath
top
engine
cover
(B)
and
crankcase
vent
hose
(C)
.
M52
engine
shown
.
M50
is
similar
.

1
.
Check
ECM
reference
voltage
to
sensor
:
"
Disconnect
harnessconnector
from
ECT
sensor
.
"
Turn
ignition
keyon
.
"
Check
for
5
volts
between
supply
voltage
wire
(brown/red)
wire
of
harness
connector
and
ground
.
"
Turn
ignition
key
off
.
"
If
voltage
is'
not
present
or
incorrect,
check
wiring
from
ECM
and
check
referencevoltage
output
at
ECM
(pin
78)
.
See
Table
i
(DM
E
3
.1)
or
Table
j
(DME
3
.3
.1)

2
.
Check
ECT
sensor
resistance
:

"
With
harnessconnector
disconnected,
check
resis-
tance
acrosssensor
terminals
.
"
Compare
tests
results
to
values
in
Table
f
.

130-
2
2



FUEL
INJECTION

Mass
air
flow
sensor,
replacing

1
.
Disconnect
harness
connector
and
intake
air
bootfrom

air
flow
sensor
.
See
Fig
.
32
.

Fig
.
32
.
To
detach
air
flow
sensor,
disconnect
harness
connector
(A)
;



3
.
Installation
is
reverse
of
removal
.
unclip
retainíng
clips
to
aír
filter
housing
(B)
;
andremove
large
hose
clamp
at
air
intake
bellows
(C)
.
M44
engine
with
traction



"
Use
a
new
copper
sealing
washer
when
installing
sen-

control
shown
.



sor
.
"
Replace
any
lost
coolant
.

2
.
Detachtwo
large
clipsat
air
filter
housing
and
work
air

flow
sensor
out
of
rubber
seal
in
filter
housing
.
Tightening
Torque

3
.
Installation
is
reverse
of
removal
.



"
Engine
coolant
temperature

"
For
ease
of
installation,
lubricate
large
rubber
seal
in



to
cylinder
head
.............
.
..
.
13
Nm
(10
ft-Ib)

air
filter
housing
with
silicone
lubricant
or
equivalent
.
"
No
adjustment
to
air
flow
sensor
is
possible
.
"
Carefully
check
that
all
hoses
and
seals
are
seated



Intake
air
temperature
(IAT)
sensor,

properly
.



replacing

Engine
coolant
temperature
(ECT)
sensor,

replacing

The
engine
coolant
temperature
(ECT)sensor
is
a
dual
temperature
sensor
.
One
circuít
provides
coolant
temperature

information
to
the
ECM
while
the
other
circuít
provides
coolant
temperature
information
to
the
instrument
cluster
.

WARNING
-

Do
not
replace
the
ECT
sensor
unless
the
engine
is
cold
.
Hot
coolant
can
scald
.

1
.
Disconnect
harness
connector
from
ECT
sensor
.
See
Fig
.
33
.

2
.
Unscrew
temperature
sensorfrom
cylinder
head
and
remove

BOSCH
DME
M5
.2
COMPONENT
REPLACEMENT

U1111
bis4a

Fig
.
33
.
M44
engine
coolant
temperature
(ECT)
sensor
located
above

oil
filter
(arrow)
.

The
intake
air
temperature
(IAT)
sensoron
cars
with
M44

engine
is
mounted
in
thetop
section
of
the
intake
air
filter

housing
.
See
Fig
.
34
.

1
.
Remove
electrical
harness
connector
from
IAT
sensor
.

2
.
Unclip
temperature
sensor
and
remove
from
air
filter

housing
.

3
.
Installation
is
reverse
of
removal
.

Throttle
position
sensor
(TPS),
replacing

The
throttle
position
sensor
is
located
on
the
side
of
the
throttle
housing
.
See
Fig
.
35
.

1
.
Unplug
harness
connector
from
sensor
.

Mass
air
flow
sensor,
replacing

1
.
Disconnect
harness
connector
and
intake
air
boots

from
air
flow
sensor
.
See
Fig
.
37
.

Fig
.
37
.
Mass
air
flow
sensor
(arrow)
on
M52
engine
.

2
.
Installation
is
reverse
of
removal
.

"
No
adjustment
to
aír
flow
sensor
is
possible
.

"
Check
intake
hoses
for
cracks
and
vacuum
leaks
.

Engine
coolant
temperature(ECT)
sensor,

replacing

The
ECT
sensor
is
a
dual
temperature
sensor
.
One
circuit

provides
coolant
temperature
information
to
the
ECM
while

the
other
circuit
provides
coolant
temperature
information
to

the
instrument
cluster
.

1
.
Remove
left-side
top
engine
cover
.

4
.
Remove
sensor
.

5
.
Installation
is
reverse
of
removal
.

"
Replace
any
lost
coolant
.

0012703

"
Use
a
new
copper
sealing
washer
when
installing
new

Tightening
Torque

"
Engine
coolant
temperature

to
cylinder
head
.....
..
.
...
......
13
Nm
(10
ft-Ib)

FUEL
INJECTION



130-
25

0012704b

Fig
.
38
.
M52
engine
:
Engine
coolant
temperature
(ECT)
sensor
(A)
is
located
beneath
top
engine
cover
(8)
and
crankcase
vent

hose
(C)
.

Intake
air
temperature
(IAT)
sensor,

replacing

The
intake
air
temperature
(IAT)
sensor
for
the
M52/S52US

engine
is
mounted
on
the
bottom
of
the
intake
manifold
.
See
Fig
.

39
.

2
.
Unclip
crankcase
venting
hose
from
cylinder
head
cov-

er
.
See
Fig
.
38
.



Fig
.
39
.
M52/S52US
engine
:
Intake
air
temperaturesensor
location
in

bottom
of
intake
manifold(arrow)
.
Throttle
housing
shown
re

3
.
Under
intake
manifold,
disconnect
harness
connector



moved
.

fromsensor
.

1
.
Disconnect
intake
air
bootfrom
throttle
housing
.
Unbolt

throttle
housing
and
¡ay
aside
.
(It
is
not
necessary
to

disconnect
throttle
cable
or
electrical
harnessconnec-

tors
from
throttle
housing
.)

sensor
.



2
.
Remove
electrical
harness
connector
from
IAT
sensor
.

3
.
Unclip
temperature
sensor
and
remove
from
intake

manifold
.

4
.
Installation
is
reverse
of
removal
.
Use
a
new
gasket
at

the
throttle
housing
.

SIEMENS
MS
41
.1
COMPONENT
REPLACEMENT