121-2
BATTERY,
STARTER,
ALTERNATOR
CHARGING
SYSTEM
TROUBLESHOOTING
Static
currentdraw,
checking
Charging
system
diagnostics
requires
special
test
equip-
ment
.
If
the
test
equipment
is
not
available,
charging
system
fault
diagnosis
can
be
performedby
an
authorized
BMW
deal-
eror
other
qualified
repair
shop
.
A
general
troubleshooting
guide
is
given
in
Table
a
.
Charging
System
Quick-Check
As
a
quick-check,
use
a
digital
multimeter
lo
measure
volt-
2
.
Disconnect
battery
negative
(-)
cable
.
age
across
the
battery
terminals
with
the
key
off
and
then
again
with
the
engine
running
.
The
battery
voltage
should
be
CAUTION-
about12
.6
volts
with
key
off
and
approximately
14
.0
volts
with
Prior
to
disconnecting
the
battery,
read
the
battery
the
engine
running
.
If
the
voltage
does
not
increase
when
the
disconnection
cautions
given
at
the
front
of
this
engine
is
running,there
is
a
fault
in
the
charging
system
.
manual
onpaga
viii
.
NOTE
-
The
regulated
voltage
(engine
running)
should
be
be-
tween
13
.5
and
14
.5,
depending
on
temperatura
and
operating
conditions
.
If
the
voltage
is
higher
than
14
.8,
the
voltage
regulator
is
most
Mely
faulty
.
Check
for
clean
and
tight
battery
cables
.
Check
the
ground
cable
running
from
the
negative
(-)
battery
terminal
lo
the
chassis
and
the
ground
cable
running
from
the
engine
lo
the
chassis
.
Check
the
alternator
drive
belt
condition
and
tension
.
If
the
battery
discharges
over
time,
there
may
be
a
constant
drain
or
current
draw
on
the
battery
.
A
small
static
drain
on
the
battery
is
normal,
but
a
largedrain
will
cause
the
battery
lo
quickly
discharge
.
Make
a
static
current
draw
test
asthe
first
step
when
experiencing
battery
discharge
.
1
.
Make
sure
ignition
and
al¡
electrical
accessories
are
switched
off
.
3
.
Connect
a
digital
ammeter
between
negative
battery
post
and
negative
battery
cable
lo
measure
current
.
See
Fig
.
1
.
Wait
at
least
one
minuta
lo
get
an
accurate
reading
.
A
range
of
about
0
lo
100
milliamps
is
normal,
dependingon
the
number
of
accessories
that
need
constant
power
.
A
current
of
400
milliamps
(0.4
amp)
or
more
may
indicate
a
problem
.
Table
a
.
Battery,
Starter
and
Charging
System
Troubleshooting
Symptom
1
Probable
Cause
1
Correctiva
Action
1
.
Engine
cranks
slowlyor
not
a
.
Battery
cables
loose,
dirty
orcor-
a
.
Clean
or
replace
cables
.
See020
Maintenance
Program
.
a
tall,
solenoíd
clicks
when
roded
.
starter
is
operated
.
b
.
Battery
discharged
.
b
.
Charge
battery,
test
and
replace
if
necessary
.
c
.
Body
ground
straploose,
dirty
or
c
.
Inspect
ground
strap,
clean,
tighten
or
replace
if
necessary
.
corroded
.
d
.
Poor
connection
at
starter
motor
d
.
Check
connections,
test
for
voltage
at
starter
.
Test
for
voltage
at
terminal
30
.
neutral
safety
or
clutch
interlock
switch
.
e
.
Starter
motor
or
solenoid
faulty
.
e
.
Test
starter
.
2
.
Battery
will
not
stay
a
.
Short
circuit
draining
the
battery
.
a
.
Test
for
excessive
current
drainwith
everything
electrical
in
the
charged
more
than
a
few
vehicle
off
.
days
.
b
.
Short
driving
trips
and
high
elec-
b
.
Evaluate
driving
style
.
Where
possible,
reduce
electrical
con
trical
drain
on
charging
system
sumption
when
making
short
trips
.
does
not
allow
battery
to
re-
charge
.
c
.
Drive
belt(s)
worn
or
damaged
.
c
.
Inspect
or
replace
multi-ribbed
belt(s)
.
See
020
Maintenance
Program
.
d
.
Battery
faulty
.
d
.
Test
battery
and
replace
íf
necessary
.
e
.
Battery
cables
loose,
dirty
orcor-
e
.
Clean
or
replace
cables
.
See
020
Maintenance
Program
.
rodad
.
f
.
Alternatoror
voltage
regulator
f
.
Test
alternator
and
voltage
regulator
.
faulty
.
3
.
Battery
losing
water
.
1
a
.
Battery
overcharging
.
1
a
.
Test
voltage
regulator
for
proper
operation
.
4
.
Lights
dim,
light
intensity
a
.
Drive
belt(s)
worn
or
damaged
.
a
.
Inspect
or
replace
multi-ribbed
belt(s)
.
See
020
Maintenance
varies
with
engine
speed
.
Program
.
b
.
Alternatoror
voltage
regulator
b
.
Test
alternator
and
voltage
regulator
.
faulty
.
c
.
Body
ground
straps
loose,
dirty
or
c
.
Inspect
ground
straps,
clean,
tighten
or
replace
as
necessary
.
corroded
.
CHARGING
SYSTEM
TROUBLESHOOTING
Alternator
brushes,
STARTER
SERVICE
inspecting
and
replacing
Regulator
brushesarenot
available
as
replacement
parts
from
BMW
.
Replacement
brushes
may
be
available
from
af-
termarket
sources,
however
.
1
.
Remove
voltage
regulator
as
described
above
.
2
.
Clean
brush
contact
sürfaces
and
measure
brush
pro-trusion
.
See
Fig
.
7
.
Check
for
battery
voltage
at
terminal
50
of
the
starter
motor
Fig
.
7
.
Regulator
brush
protrusion
(A)
.
with
the
key
in
the
start
position
.
See
Fig
.
8
.
If
voltage
is
not
present,
check
the
wiring
between
the
ignition
switch
and
the
starter
terminal
.
If
voltage
is
present
and
no
other
visible
wir
Voltage
Regulator
ing
faults
can
be
found,
the
problem
is
most
likely
interna¡in
"
Brush
protrusion
(minimum)
.......
.
..
5
mm
(
1
/4
in
.)
the
starter
motor
.
3
.
To
replace
brushes,
carefully
and
as
quickly
as
possi-
ble,
unsolder
brush
lead
from
brush
holder
termina¡,
withdrawing
brush
from
holder
at
same
time
.
4
.
Remove
any
traces
of
solder
frombrush
holder
termi-
nal
using
solder
wick
.
5
.
Fit
spring
into
brush
holder
and
inserí
new
brush
.
6
.
Guide
brush
lead
into
terminal
and
solder
into
place
.
Check
for
free
movement
of
brushes
when
solder
cools
.
7
.
Check
brush
slip
rings
in
alternator
for
wear
.
Lightly
clean
slip
rings
using
fine
abrasive
cloth
.
BATTERY,
STARTER,
ALTERNATOR
121-
7
Starter
Troubleshooting
If
the
starter
tucos
the
engine
slowlyor
fails
to
operate
when
the
ignition
isin
the
start
position,
check
the
battery
first
.
In-
spect
the
starter
wires,
terminals,
and
ground
connections
for
good
contact
.
In
particular,
make
sure
the
ground
connections
between
the
battery,
the
body
and
the
engine
are
completely
clean
and
tight
.
If
no
faults
can
be
found,
the
starter
may
be
faulty
and
should
be
replaced
.
NOTE
-
"
Starting
in1194,
a
factory-installed
drive-away
protec-
tion
system,
alsoreferred
to
as
EWS
or
EWS
11,
was
used
on
all
E36
cars
.
This
system
prevenís
operation
of
the
starter
when
the
system
is
engaged
.
See
515
Central
Locking
and
Anti-theft
.
"
On
cars
with
automatic
transmission,
a
starter
relay
and
a
neutral
safetyswitchare
used
to
present
theen-
ginefrom
starting
in
gear
positions
other
than
park
or
neutral
.
ff
voltage
is
not
present
atterminal
50
with
the
key
in
the
startposition,
check
these
components
To
make
the
most
accurate
check
of
the
battery
cables
and
starterwiring,
make
a
voltage
drop
test
on
the
cables
and
wir-
ing
as
described
in
600
Electrical
System-General
.
Terminal
30
'
\
/
Terminal
30h
0012518
8
.
Reinstall
regulator
and
alternator
.
Fig
.
8
.
Typical
starterwiring
terminal
identification
.
Large
wireat
ter-
minal
30
is
direct
battery
voltage
.
Smaller
wire
at
terminal
50
operates
starter
solenoid
via
ignition
switch
.
STARTER
SERVICE
121-
8
BATTERY,
STARTER,
ALTERNATOR
1f
the
solenoid
audibly
cliicks
but
the
motor
does
not
turn,
Starter,
removing
and
installing
switch
on
the
lights
andtum
the
key
to
the
start
position
.
lf
the
(6-cylinder
engine
with
lights
go
out
while
attempting
to
start,
the
battery
cable
may
be
manual
transmission)
loose
or
the
starter
may
have
a
short
circuit
.
If
the
lights
stay
on,the
solenoid
is
most
likely
atfault
.
The
starter
on
a
6-cylinder
car
with
manual
transmission
is
Starter,
removing
and
installing
(4-cylinder
engine)
1
.
Disconnect
negative
(-)
battery
cable
.
1
.
Disconnect
negative
(-)
cable
from
battery
.
CAUTION-
Prior
to
disconnecting
the
battery,
read
the
battery
disconnection
cautions
given
at
the
front
of
this
manual
on
page
viii
.
2
.
Remove
guide
tube
for
oil
dipstick
.
3
.
Raise
vehicle
.
WARNING
-
Make
sure
the
car
ís
stable
and
wefl
supported
at
all
times
.
Use
a
professional
automotive
lift
or
jack
stands
designed
forthe
purpose
.
A
floor
jack
is
not
adequate
support
.
4
.
Disconnect
wiring
from
starter
.
5
.
Remove
top
and
bottom
starter
bolts
.
Bottom
bolt
must
be
removed
from
below
car
.
Remove
starter
support
bracket,
if
applicable
.
removed
from
below
.
2
.
Raise
vehicle
.
3
.
Remove
reinforcing
cross
bracefromunder
transmís-
sion,
if
applicable
.
4
.
Remove
cover
from
fuel
filter
and
fuel
lines
on
left
side
underneath
car,
if
applicable
.
Detach
fuel
lines
and
har-
ness
connectors
from
retainingbrackets,
as
necessary
5
.
Disconnect
wiring
from
starter
.
6
.
Loosen
andremove
bolts
and
nuts
fastening
starter
to
transmission
bell
housing
and/or
engine
block
.
Remove
starter
supportbracket
.
7
.
Remove
starter
from
below
.
8
.
Check
starter
pinion
gear
and
flywheel
teeth
for
dam-
age
.
9
.
Installation
is
reverse
of
removal
.
6
.
Pull
starter
downward
and
turn
until
solenoid
is
at
top,
Tightening
Torques
then
remove
from
car
.
"
Re¡
nforcing
cross
brace
to
chassis
(M10)
..
...............
42
Nm
(31
ft-Ib)
7
.
>Check
starter
pinion
gear
and
flywheel
teeth
for
dam-
"
Starter
to
engine
block
(M10
bolt)
...
50
Nm
(37
ft-Ib)
age
.
"
Support
bracket
to
starter
(M5
nut)
...
5
Nm
(44
in-lb)
"
Support
bracket
8
.
Installation
is
reverse
of
removal
.
to
engine
block
(M10
bolt)
.........
47
Nm
(35
ft-Ib)
"
Wire
to
terminal
50
(M6
nut)
.........
6
Nm
(53
ín-Ib)
"
Wire
to
terminal
30
(M8
nut)
.........
12
Nm
(9
ft-lb)
Tightening
Torques
"
Starter
to
engine
block
(M10
bolt)
...
50
Nm
(37
ft-lb)
Wire
to
terminal
50
(M6
nut)
........
6
Nm
(53
in-lb)
"
Wire
toterminal
30
(M8
nut)
...
,
..:.
12
Nm
(9
ft-Ib)
STARTER
SERVICE
121-1
O
BATTERY,
STARTER,
ALTERNATOR
9
.
Remove
starter
from
above
.
10
.
Check
starter
pinion
gear
and
flywheel
teeth
for
dam-
age
.
11
.
Installation
is
reverse
of
removal
.
Tightening
Torques
"
tntakemanifold
to
cylinder
head
M7
nut
...
.
................
...
.
15
Nm
(11
ft-Ib)
M8
nut/bolt
.............
.
.
..
...
22
Nm
(16
ft-Ib)
"
Starter
to
engine
block
(M10
bolt)
...
50
Nm
(37
ft-Ib)
"
Support
bracket
to
starter
(M5
nut)
...
5
Nm
(44
in-lb)
"
Support
bracket
to
engine
block
(M10
bolt)
.
.
..
..
...
47
Nm
(35
ft-Ib)
"
Wire
toterminal
50
(M6
nut)
.
..
.....
6
Nm
(53
in-lb)
"
Wire
toterminal
30
(M8
nut)
...
.....
12
Nm
(9
ft-Ib)
Solenoid
switch,
removing
and
installing
1
.
Remove
starter
as
described
above
.
Tightening
Torque
2
.
Remove
cover
from
solenoid
switch
.
"
Field
winding
strap
to
starter
(M8)
...
.
12
Nm
(9
ft-Ib)
3
.
Disconnect
fieid
winding
strap
between
starter
motor
and
solenoid
switch
.
NOTE-
The
condition
of
the
field
winding
strap
is
critical
.
If
it
is
damaged,
bumed
or
partially
melted
through,
a
new
or
rebuilt
starter
motor
is
needed
.
4
.
Remove
solenoidswitch
mounting
screws,
and
sepa-
,
rate
solenoid
from
starter
.
See
Fig
.
12
.
CAUTION-
When
installing
fieid
winding
strap
to
starter,
posi-
tion
it
so
that
it
does
not
contact
the
starter
body
.
STARTER
SERVICE
131~184
Fig
.
12
.
Starter
solenoid
mounting
screws
(arrows)
are
tight
.
Use
en
impact
screwdriver
to
loosen
the
screws
.
5
.
Installation
is
reverse
of
removal
.
Lubricate
solenoid
pistos
with
light
grease
.
130-
6
FUEL
INJECTION
Warnings
and
Cautions
For
personal
safety,
as
well
as
the
protection
of
sensitive
electronic
components,
the
following
warnings
and
cautions
should
be
adhered
to
when
working
on
the
engine
manage-
ment
system
.
GENERAL
WARNING
-
"
The
ignition
system
produces
high
voltages
that
can
be
fatal
.
Avoid
contact
with
exposed
termi-
nals
.
Use
extreme
caution
when
working
onacar
with
the
ignition
switched
on
or
the
engine
run-
ning
.
"
Do
not
touch
or
disconnect
any
high
voltage
ca-
bles
from
the
coils
or
spark
plugs
while
the
engine
is
running
or
beingcranked
by
the
starter
.
"
Connect
and
disconnect
the
DME
system
wiring
and
test
equipment
leads
only
when
the
ignition
is
switched
off
.
"
Gasoline
is
highly
flammable
and
fts
vaporsare
explosive
.
Do
not
smoke
or
work
on
a
car
near
heaters
or
other
fire
hazards
when
diagnosing
and
repalring
fuel
system
problems
.
Have
a
tire
extinguisher
avaílable
in
case
of
an
emergency
.
"
When
working
onan
open
fuel
system,
wear
suit-
able
hand
protection,
asprolonged
contact
wfth
fuel
can
cause
illnesses
and
skin
disorders
.
"
Renew
fuel
system
hoses,
clamps
and
O-rings
any
timethey
are
removed
.
"
Before
makingany
electrical
tests
that
require
the
engine
to
be
cranked
using
the
starter,
disable
the
ignition
system
as
described
in
120
Ignition
System
.
CAUTION-
"
Prior
to
disconnecting
the
battery,
read
the
bat-
tery
disconnectinn
cautions
given
at
the
front
of
this
manual
onpage
vifi
.
"
Do
not
connect
any
test
equipment
that
delivers
a
12-volt
power
supply
to
terminal
15
(+)
of
the
ig-
nitioncoil
.
The
current
flow
may
damage
the
ECM
.
In
general,
connect
test
equipment
only
as
speclfied
by
BMW,
this
manual,
or
the
equipment
maker
.
"
Only
use
a
digital
multlmeter
for
electrical
test
.
"
Only
use
an
LED
test
light
for
quick
tests
.
"
Disconnecting
the
battery
may
erase
fault
code(s)
stored
in
memory
.
Check
for
fault
codes
prior
to
disconnecting
the
battery
cables
.
ff
the
Check
Engine
light
ís
illuminated,
see100En-
gine-General
for
DME
fault
code
information
.
ff
any
other
system
faults
have
been
detected
(indi-
catedbyan
illuminated
warning
light),
see
an
au-
thorized
BMW
dealer
.
Additional
systems
with
self-diagnostic
capabilities
include,
ABS
(Anti-
lock
brakes),
SRS
(Airbags),
EML
and
ASC+T
and
AST
(Traction
Control)
.
"
Do
not
run
the
engine
wfth
any
of
the
spark
plug
wires
dlsconnected
.
Catalytic
converter
damage
may
result
.
"
Always
waitat
least
40
seconds
afterturning
off
the
ignition
before
removing
the
engine
control
module
(ECM)
connector
.
ff
the
connector
isre-
moved
before
this
time,
residual
power
in
the
sys-
tem
relay
may
damage
the
control
module
.
"
Cleanliness
is
essential
when
working
onan
open
fuel
system
.
Thoroughly
clean
fuel
line
con-
nections
and
surroundlng
areas
before
loosen-
ing
.
Avoid
moving
the
car
.
Only
fnstall
cleanparts
.
"
Fuel
system
cleaners
and
other
chemical
addi-
tives
other
than
those
specifically
recommended
by
BMW
may
damage
the
catalytic
converter,
the
oxygensensor
or
other
fuel
supply
components
.
3
.
Observe
fuel
pressure
gauge
after
20
minutes
.
The
pressure
shouldnot
drop
off
more
than
0
.5
bar
from
system
pressure
listed
in
Tablec
.
4
.
When
finished
testing,
disconnect
pressure
gauge
and
reconnect
fuel
line
.
If
the
fuel
system
does
not
maintain
pressure,
check
visual-
¡y
for
leaks
in
fuel
lines
orat
unions
.
Leaks
can
also
be
due
to
a
leaking
injector
or
a
faulty
fuel
pump
check
valve
.
Check
the
pump
check
valve
by
repeating
the
test,
butbefore
turning
the
fuel
pump
off,
pinch
off
theretum
line
at
the
fuel
rail
.
If
the
pressure
is
now
maintained,
the
fault
is
most
likely
the
fuel
pump
check
valva
.
Tabla
c
.
Fuel
Pressure
Specifications
Engine
1
Fuel
pressure
4-cytinder
1
3
.0
t
0
.2
bar
(43
.5
t
2
.9psi)
6-cytinder
M50/S50US
engine
3
.0
t
0
.2
bar
(43
.5
±2
.9psi)
M52/S52US
engine
3
.5
f
0
.2
bar
(51
t
2.9psi)
Fuel
pressure
regulator
response
to
engine
load,
testing
1
.
With
fuel
pressure
gauge
connected,
reinstallfuel
pump
relay
.
Start
engine
and
allow
it
to
idle
.
NOTE-
The
fuel
pressure
should
be
lower
by0
.4-0.7
bar
from
the
specifications
listed
in
Table
c
.
Engine
vacuum
act-
ing
on
the
fuel
pressure
regulator
diaphragm
reduces
the
fuel
pressure
.
2
.
With
engine
idling,
remove
vacuum
hose
from
regula-
tor
.
Pressure
should
increase
.
3
.
Reconnecthose
and
check
that
pressure
decreases
.
4
.
When
finished
testing,
disconnect
pressure
gauge
and
reconnect
fuelline
.
Tighten
hose
clamp
.
0013190
Fig
.
13
.
For
electrical
tests,
4-cytinder
fuel
injector
harnessduct
can
be
If
fuel
pressure
does
not
drop
with
the
vacuum
hose
con-
accessed
between
intake
manifold
and
cytinder
head
cover
.
nected
and
no
faulty
are
found
with
fuel
the
pressure
regulator
vacuum
hose,
the
fuel
pressure
regulator
is
faulty
.
1
.
Check
that
ECM
signal
is
present
atinjector
connector
.
NOTE-
A
cracked
or
leaktng
pressure-regulator
vacuum
hose
may
cause
en
erratic
tdle
.
FUEL
INJECTION
130-
11
Fuel
rail
and
injectors,
checking
The
fuel
injectors
are
switched
on
and
off
(opened
and
closed)
by
the
ECM
.
The
injectors
are
connected
to
a
com-
mon
fuel
supply,
callad
the
fuel
rail
.
The
fuel
injectors
are
removed
by
first
removing
the
com-
plete
fuel
rail
assembly
and
then
unclipping
the
injectors
from
the
fuel
rail
.
CA
UTION-
Use
only
a
digital
multimeter
or
an
LED
injector
tester
when
testing
injectors
or
wiring
.
Use
of
ananalog
VOM
or
incandescent
testlight
may
dam-
age
the
engine
control
module
.
NOTE-
"
On
4-cytindercars
pry
up
the
injector
wiring
duct
and
then
pry
off
the
cover
.
See
Fig
.
13
.
"
On
6-cytinder
cars
it
is
necessary
to
remove
the
top
engine
cover(s)
to
access
the
fuel
rail
and
injectors
.
"
Back
probe
injector
harness
connector
using
digital
voltmeter
.
See
Fig
.
14
.
"
Operate
starter
or
run
engine
and
check
for
pulsad
voltage
signal
.
"
Repeat
for
each
injector
.
NOTE
-
To
quick-check
if
en
injectorfunctioning,
place
a
screw-
driver
or
stethoscope
on
the
injector
with
the
engine
running
.
If
the
injector
is
operating,there
should
been
audible
buzz
.
FUEL
DELIVERYTESTS
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
.