1995 BMW M3 fault

515-4



CENTRAL
LOCKING
AND
ANTI-THEFT

11
.
Installation
is
reverse
of
removal
.
Keep
in
mind
the
fol-



4
.
Remove
screws
mounting
bottom
of
window
rear
track

lowing
:



to
door
.
See
Fig
.
9
.

"
Make
sure
rubber
seal
for
handle
is
correctly
posi-

tionedbefore
tightening
mounting
fasteners
.

"
Install
exteriortrim
piece
and
then
use
a
hooked
tool
to

pull
locking
plate
into
locked
position
.
Make
sure
door

handle
trim
contacts
body
evenly
before
locking
trim

in
place
.

"
Use
new
mounting
bolts
when
reinstalling
the
side-im-

pactairbag
to
the
door(where
applicable)
.
Reset
SRS

warning
light
and
clear
SRS
fault
memory
using
spe-

cial
test
equipment
.
See
721
Airbag
System
(SRS)
.

"
Reconnect
al¡
harness
connectors
(including
power

window
motor)before
installing
door
panel
.

"
Secure
wire
harnesses
withwire
ties
.

"
Adjust
and
reinitialize
windows
.
See
512
Door
Win-

dows
.

Tightening
Torque

"
Collar
nut
to
doorhandle
..........
10
Nm
(89
in-lb)

1.
Remove
rear
door
panel
and
vapor
barrier
as
described

in
411
Doors
.

2
.
Remove
window
from
rear
dooras
described
in
512

Door
Windows
.

3
.
Disconnect
andremove
inside
door
handle
.
See
Fig
.
8
.

0013073

Fig
.
8
.



Inside
door
handle
retaining
screw
(A)
Unhook
linkage
from
handle
at
B
.

DOOR
HANDLES
AND
LOCKS

Fig
.
9
.



Rear
window
track
lower
fasteners
(arrows)
.

Reardoor
lock,
removing
and
installing



5
.
Remove
window
rear
track
top
screw
and
move
track

aside
.
See
Fig
.
10
.

Fig
.
10
.
Rear
window
track
top
screw
(arrow)
.

6
.
Remove
screw
from
lock
button
linkage
rod
retainer
.
Lift

rod
out
of
retaining
clip
.
See
Fig
.
11
.

7
.
Disconnect
door
lock
harnessconnector
.

8
.
Remove
door
lock
screws
.
See
Fig
.
12
.

0013085

9
.
Move
lock
upslightly
to
disengage
from
exterior
handle

linkage
.
Remove
lock
from
inside
door
.

515-6



CENTRAL
LOCKING
AND
ANTI-THEFT

6
.
Remove
door
handle
assembly
from
inside
door
.

7
.
Installation
is
reverse
of
removal
.
Keep
in
mindthe
fol-

lowing
:

"
Make
sure
rubber
seal
for
handle
is
correctly
posi-

tionedbefore
tightening
mounting
fasteners
.

"
Install
exterior
trim
piece
and
then
use
a
hooked
toolto

pull
locking
plate
into
locked
position
.
Make
sure
door
handle
trim
contacts
body
evenly
before
lockingtrim

in
place
.

"
Reconnect
all
harness
connectors
(including
power

window
motor)before
installing
door
panel
.

"
Secure
wire
harnesses
withwire
ties
.

"
Adjust
windowas
described
in
512
Door
Windows
.

Tightening
Torque

"
Rear
door
handle
mounting
screws
..
10
Nm
(89
in-lb)

NOTE

If
the
striker
backup
plate
fafls
into
the
body
cavlty,
it
can
be
retrieved
after
removing
the
inside
trim
from
the
B-pillar
(door-post
pillar)
.

Tightening
Torque

"
Striker
plate
to
body
pillar
..........
28
Nm
(20
ft-lb)

LOCKING
ACTUATORS

Door
Locking
Actuator

The
front
door
lock
mechanism
and
actuator
are
shown
in
Fig
.
15
.
The
rear
door
lock
and
actuator
are
similar
.
The
lock
must
first
be
removed,
as
described
earlier,
to
replace
the
ac-
tuator
.

if
defective
.

LOCKING
ACTUATORS

Connections
to
door
handle

®
o

_



Attaching
pin
0

O~
Lock
mechanism

0012082

Fig
.
15
.
Front
door
lock
mechanism
and
related
parts
.
Rear
lock
mechanism
is
similar
.

Door
striker,
replacing



Luggage
compartment
locking
actuator,

removing
and
installing
The
door
striker
contains
an
electrical
contact
switch
.
If
the

switch
is
faulty,
the
striker
must
be
replaced
.
To
remove
the



1
.
Raise
trunk
lid
.
Remove
tool
kit
and
trunk
lid
trim
panel
.

striker,
remove
the
mounting
bolts
.
Disconnect
the
harness



See
Fig
.
16
.

connector
from
the
striker
.

0013162

Fig
.
16
.
Trunk
lid
trim
and
tool
kit
retainíng
screws
and
clips
(arrows)
.

2
.
Disconnect
actuating
rod
from
lock
.
See
Fig
.
17
.

3
.
lJnplug
two
wíring
connectors
from
actuator
.
See
Fig
.

18
.

NOTE
-

"
lf
just
one
of
the
centrallocking
drives
does
not
oper-



NOTE-

ate,
the
lockinglinkage
could
be
frozen
orstiff
enough



The
actuator
is
adjustable
.
Matchmark
the
attaching
to
prevent
actuatonof
the
drive
.
Try
remove
the
finte-



screws
before
removal
.

rior
doorpanel
and
lubricating
the
locking
linkage
as
the
first
step
.



4
.
Remove
actuator
attaching
screws
.
Pull
actuator
back-

"
The
actuator
is
not
serviceable
and
mustbe
replaced



wards
from
behind
metal
shield
to
remove
.

5
.
installation
is
reverse
of
removal
.
Align
actuator
screws
with
matchmarks
during
installation
.

Convertible
top
drive
motor,
replacing



5
.
Working
in
convertible
top
storage
compartment
be-
hind
driver's
seat,
remove
convertible
top
linkage
rods
1
.
Open
convertible
top
partially,
stopping
when
convert-



from
top
of
motor
.
Refer
to
Fig
.
11
.
ible
top
lid
is
fully
upen
.
Remove
lid
.

2
.
Release
luggage
compartment
lock-out
by
pressing
on
microswitch
in
right
convertible
top
lid
latch
.
See
Fig
.

14
.

0012745

Fig
.
14
.
Rightside
convertible
top
lid
latch
.
Arrow
points
to
location
of
luggage
compartment
lock-out
microswitch
.

3
.
Open
luggage
compartment
.
Remove
trim
and
inner

lining
from
left
side
of
compartment
.

4
.
Disconnect
electrical
harness
connectors
at
top
motor
.

Release
emergency
release
cable
from
lever
.
Push
le-

ver
up
to
release
motor
.
See
Fig
.
15
.

uu12759

Fig
.
15
.
Convertible
top
motor
(A)
and
release
lever
(B)
in
luggage

compartment
.

CONVERTIBLE
TOP



541-
7

6
.
Remove
four
fastenersholding
motor
to
body
and
re-

move
motor
through
luggage
compartment
.
See
Fig
.

16
.

0012761

Fig
.
16
.
Convertible
top
motor
mountingscrews
(arrows)
.
Gasket
(A)
mustbe
renewed
when
motor
is
replaced
.

7
.
Installation
is
reverse
of
removal
.
Keep
the
following
in

mind
:

"
Replace
sealing
gasket
between
top
of
motor
and

body
.

"
Securemotormountingscrews
with
Locktite
®
270
or
equivalent
.

Tightening
Torque

"
Convertible
top
motor
to
body

mountingscrews
...
...
.
.
.........
10
Nm
(7
.5
ft-Ib)

Convertible
Top
Emergency
Operation

A
malfunction
in
the
electrical
system
or
another
fault
in
the

convertible
top
mechanism
can
cause
the
automatic
or
semi-
automatic
top
to
be
stuck
in
open,
shut,
or
intermediate
posi-

tion
.
The
following
general
procedures
are
suggested
in
order

to
close
the
top
in
an
emergency
situation
.
Resetting
proce-

dures
for
convertible
top
synchronization
after
emergency
clo-

sure
are
beyond
the
scope
of
this
manual
.

Main
Motor
.
To
release
thetop
linkage
from
the
motor,
lift

the
left
comer
of
the
rearseat
to
access
emergency
release

handle
.
See
Fig
.
17
.

POWER
CONVERTIBLE
TOP

Convertible
Top
Lid

The
components
of
the
convertible
top
lid
are
shown
in
Fig
.
20
.

Fig
.
20
.
Components
of
the
convertible
top
lid
.

ROLLOVER
PROTECTION
SYSTEM

The
lid
latches
are
cable
operated
by
a
drive
motor
located
in
the
left
sideof
the
luggagecompartment,
behind
the
trim
lin-

er
.
The
same
motor
is
used
to
raise
and
lower
the
lid
during

automatic
convertible
topoperation
.

The
latch
cables
must
be
adjusted
so
that
the
lidfits
snugly
against
the
body
when
locked
.

The
lid
drive
motor
can
be
removed
and
replaced
from
the

luggage
compartment
.

Two
spring-locaed
cassettes
are
mounted
behind
the
rear
seat
.
A
single
rollover
sensor,
mounted
on
the
left
cassette,
signals
the
convertible
top
module
(CVM)
of
animminent
roll-
over,
whereupon
the
module
triggers
both
cassettes
within

3j10th
of
a
second
.
See
Fig
.
21
.

Once
the
cars
ignition
has
been
switched
on,
the
rollover

sensor
performs
a
self-test
lasting
6
seconds
.
During
this
time

a
yellow
warning
light
is
lit
on
the
dashboard
.
If
thewarning
lightfails
to
go
out
after
6
seconds,
this
means
that
a
fault
has

been
detected
in
the
system
.
The
fault
is
stored
in
the
CM

Faults
canbe
retrieved
and
diagnosedby
special
diagnostic

equipment
.

NOTE-

Diagnosis
of
the
convertible
top
and
the
Rollover
Pro-
tection
System
are
beyond
the
scope
of
this
book
.
Your
authorized
BMW
dealer
has
the
proper
diagnostic
equipment
and
tools
to
carry
out
these
tasks
.

CONVERTIBLE
TOP



541-
9

Fig
.
21
.
Construction
of
the
rollover
protection
cassette
.

After
deployment,
thedetent
pawl
in
a
rollover
protection
cassette
can
be
retracted
using
the
special
tool
in
the
tool
kit,
fitted
to
the
screwdriver
handle
.
The
rear
seatheadrest
needs
to
be
raised
for
this
procedure
.

WARNING
-

Ensure
that
the
area
above
and
adjacent
to
the
roll-
over
bars
remains
clear
and
unobstructed
at
all
times
.

CAUTION-

"
Itis
not
possible
to
close
the
convertible
top
with
the
rollover
bars
extended
.

"
If
a
hardtop
is
mounted,
be
sure
to
install
the
pro-
tective
rollover
bar
covers
provided
with
the
hard-
top
to
prevent
damaglng
the
rear
window
in
case
of
deployment
.

0012744

ROLLOVER
PROTECTION
SYSTEM

600-2



ELECTRICAL
SYSTEM-GENERAL

CAUTION
-

"
Always
turn
off
the
engine
and
disconnect
the

negative
()
cable
from
the
batterybefore
remov-

ing
any
electrical
components
.
Disconnecting
the

battery
may
erase
fault
code(s)
stored
in
control

module
memory
.
Check
for
fault
codes
using
spe-
cial
BMW
diagnostic
equipment
.

"
Prior
to
disconnecting
the
battery,
read
the
bat-

tery
disconnection
cautions
given
at
the
front
of

this
manual
onpage
viii
.

"
Connect
and
disconnect
ignition
system
wires,
multiple
connectors,
and
ignition
test
equipment
leads
only
while
the
ignition
is
off
.

"
Do
not
disconnect
the
battery
with
engine
run-

ning
.

"
Do
not
quick-charge
the
battery
(for
boost
start-
ing)
for
longer
than
one
minute,
and
do
not
ex-
ceed
16
.5
volts
at
the
battery
with
the
boosting
cables
attached
.
Wait
at
feast
one
minute
before
boosting
the
battery
a
second
time
.

"
Do
not
usea
test
famp
that
has
a
normal
incan-

descent
bulb
to
test
circuits
contafning
electronic
components
.
The
high
electrical
consumptionof
these
test
lamps
may
damage
the
components
.

"
Do
not
use
an
analog
meter
.
Use
onfy
a
digital
multimeter
.

"
Many
of
the
solid-state
modules
are
static
sensi-
tive
.
Static
discharge
will
permanently
damage
them
.
Always
handle
the
modules
using
proper
static
prevention
equipment
and
techniques
.

"
To
avoid
damaging
harness
connectors
or
relay
panel
sockets,
use
jumper
wires
with
flat-blade
connectors
that
are
the
same
size
as
the
connec-
tor
or
relay
terminals
.

"
Always
switch
a
digital
multimeter
to
the
appropri-
ate
function
and
range
before
making
test
con-
nections
.

"
Do
not
tryto
start
the
engine
of
a
carwhich
has
been
heated
above176°F
(80°C),
(for
example,
in
a
paint
dryingbooth)
.
Allow
it
to
cool
to
normal
temperature
.

"
Disconnect
the
battery
before
dolng
any
electric
welding
on
the
car
.

"
Do
not
wash
the
engine
while
it
is
runnfng,
or
any-
time
the
ignition
is
switched
on
.

WIRING
DIAGRAMS

Electrical
Test
Equipment

Many
of
the
electrical
tests
described
in
this
manual
call
for

measuring
voltage,
currentorresistanceusing
a
digital
multi-

meter
(DMM)
.
Digital
meters
are
preferred
for
precise
mea-

surements
and
for
electronics
work
because
they
are
generally
more
accuratethan
analog
meters
.
The
numerical

display
is
alsoless
likely
to
be
misread,
since
there
is
no
nee-

dle
position
to
be
misinterpreted
by
reading
at
an
angle
.

An
LED
test
light
is
a
safe,
inexpensive
tool
that
can
be
used

to
perform
many
simple
electrical
tests
that
would
otherwise

require
a
digital
multimeter
.
The
LED
indicates
when
voltage

is
present
between
anytwo
test-points
in
a
circuit
.

CA
UTION-

"
Choose
test
equipment
carefully
.
Use
a
digital

multimeter
with
at
leadt
10
megaohm
input
im-

pedance,or
an
LED
test
light
.
An
analog
meter
(swing-need1e)
ora
test
light
with
a
normal
incan-
descent
bulb
may
draw
enough
current
to
dam-
age
sensitive
electronic
components
.

"
An
ohmmeter
must
not
beused
to
measure
resis-
tance
on
solidstate
components
suchas
controlunits
or
time
delay
relays
.

"
Always
disconnect
the
battery
before
making
re-

sístance
(ohm)
measurements
on
the
circuit
.

WIRING
DIAGRAMS

The
wiring
diagrams
shown
in
Electrical
Wiring
Diagrams

have
been
specially
designed
to
enable
quick
and
efficientdi-

agnosis
and
troubleshooting
of
electrical
malfunctions
.

Wiring
Codes
and
Abbreviations

A
lot
of
information
is
included
in
each
wiring
diagram
if
you
know
how
to
read
them
.
Wire
colors
in
the
diagrams
are
ab-

breviated
.
Combined
color
codes
indicate
a
multi-colored
wire
.
For
example
the
code
BLU/RED
indicates
a
Blue
wire

with
a
Red
stripe
.

Many
electrical
components,
connectors,
fuses,
and

ground
locations
are
identified
using
a
unique
number
.
Each

of
there
numbers
corresponds
to
a
particular
part
in
the
circuit
commonly
found
in
Electrical
Wiring
Diagrams
.

NOTE
-

Sometimes
the
color
of
en
installed
wire
may
be
differ-
ent
than
the
one
on
the
wiring
diagram
.
Don't
be
con-
cerned
.
Just
be
sure
lo
confirm
that
the
wire
connects
lo
the
proper
terminals
.

Wire
color
codes

"
BLU
.........
.
..
..
...
.
.................
Blue

"
BRN
....:....
.
..
..
...
..
...............
Brown

"
YEL
.........
.
..
..
...................
.Yellow

"
GRN
.........
.
..
..
...
.
................
creen

"
G
RY
.......
.
.
.
..
..
.....................
G
ray

"
ORG
.........
.
..
..
...
.
..............
.Orange

"
RED
......
...
.
.
..
.....................
.Red

"
BLK
.........
.
..
..
...
.
................
Black

"
VIO
..........
.
..
...
..
..
.......
.
.......
Violet

"
WHT
.........
.
.
....
.
...
:..............
White

Table
a
.
Terminal
and
Circuit
Numbers

Number



1
Circuít
description

1



j
Low
voltage
switched
terminal
of
coi¡

4



1
High
voltage
center
termina¡
of
coi¡

+x



Originates
atignition
switch
.
Supplies
powerwhen
the
ignition
switch
is
in
the
PARK,
RUN,
or
START
position

15



Originates
atignition
switch
.
Supplies
powerwhen
ignition
switch
is
in
RUN
or
START
position

30



Battery
positive
(+)
voltage
.
Supplies
power
whenever
battery
is
connected
.
(Not
dependent
on
ignition
switch
position,
unfused)

31



1
Ground,
battery
negative
(-)
terminal

50



Supplies
power
from
battery
to
starter
solenoid
when
ignition
switch
isin
START
position
only

+54



Originates
atignition
switch
.
Supplies
power
when
ignition
switch
isin
the
RUN
position
only

85



1
Ground
side
(-)
ofrelay
coil

86



1
Power-in
side
(+)
ofrelay
coil

87



1
Relay
actuatedcontact

D



Alternator
warning
light
and
field
energizing
circuit

ELECTRICAL
SYSTEM-GENERAL
600-
3

Additional
abbreviations
shown
in
the
wiring
diagrams
are

given
below
.

Abbreviations

"
ABS
........
.
...
.
...
.
..........
antilock
brakes

"
A/C
........
.
...
..
..
.
.........
.airconditioning

"
AST/ASC+T
.......
...
.
.
.......
al¡
season
traction

"
CONV
.......
.
.
...
.................
convertible

"
DME
........
.
.
...
.......
digital
motor
electronics

"
ECM



.......
.
...
..
..
.
..
electronic
control
module

"
EWS/EWS
II
......
...
.
.
coded
driveaway
protection

"
SRS
........
.
supplemental
restraint
system-airbag

"
TCM
........
.
..
....
.
transmission
control
module

"
ZKE
(94-98
models)
..
..
.
...
central
body
electronics

"
ZVM
(92-93
models)
...
.
.
..
.
.......
central
locking

ELECTRICAL
TROUBLESHOOTING

Most
terminals
are
identified
by
numbers
on
the
compo-

nents
and
harness
connectors
.
The
terminal
numbers
for
ma-



Four
things
are
required
for
current
toflow
in
any
electrical

jor
electrical
connections
are
shown
in
the
diagrams
.
Though



circuit
:
a
voltagesource,
wires
or
connections
to
transport
the

many
terminal
numbers
appear
only
once,
severa¡other
num-



voltage,
a
load
or
device
that
uses
the
electricity,
and
a
con-
bers
appear
in
numerous
places
throughout
the
electrical
sys-



nection
to
ground
.
Most
problemscanbefound
using
a
digital

tem
and
identify
certain
types
ofcircuits
.
Some
of
the
most



multimeter
(volt/ohm/amp
meter)to
check
for
voltage
supply,

common
circuit
numbers
are
listed
below
in
Table
a
.



for
breaks
in
the
wiring
(infinite
resistance/no
continuity),
orfor

a
path
to
ground
that
completesthe
circuit
.

Electric
current
is
logical
in
its
flow,
always
moving
from
the

voltage
sourcetoward
ground
.
Electricalfaults
can
usually
be

located
through
a
process
of
elimination
.
When
troubleshoot-

ing
a
complex
circuit,
separate
the
circuit
into
smaller
parts
.

The
general
testsoutlined
below
may
be
helpful
in
finding

electrical
problems
.
The
information
is
most
helpful
when

used
with
the
wiring
diagrams
.

Be
sure
to
analyze
the
problem
.
Use
the
wiring
diagrams
to

determine
the
most
likely
cause
.
Getan
understanding
of
how

the
circuit
works
by
following
the
circuit
from
groundback
to

the
power
source
.

When
making
test
connections
at
connectors
andcompo-

nents,
use
care
to
avoidspreading
or
damaging
the
connec-

tors
or
terminals
.
Some
tests
may
require
jumper
wires
to

bypass
components
or
connections
in
the
wiring
harness
.

When
connecting
jumper
wires,
use
bladeconnectors
at
the

wire
ends
that
match
the
size
of
the
terminal
being
tested
.
The

small
interna¡
contacts
are
easily
spread
apart,
and
this
can

cause
intermittent
or
faultyconnections
that
can
leadto
more

problems
.

ELECTRICAL
TROUBLESHOOTING

600-
4



ELECTRICAL
SYSTEM-GENERAL

Voltage
and
Voltage
Drops

The
wires,
connectors,
and
switches
that
carry
current
are

designed
with
very
low
resistance
so
that
current
flows
with
a

minimum
loss
of
voltage
.
A
voltage
drop
is
caused
by
higher
than
normal
resistance
in
a
circuit
.
This
additional
resistance

actually
decreases
or
stops
the
flow
of
current
.
A
voltage
drop

can
be
noticed
byproblems
ranging
fromdim
headlights
to
sluggish
wipers
.
Some
common
sources
of
voltage
drops
are
corroded
or
dirty
switches,
dirty
or
corroded
connections
or

contacts,
and
loose
or
corroded
ground
wires
and
ground
con-

nections
.

A
voltage
drop
test
is
a
good
test
to
make
if
current
is
flowing
through
the
circuit,
butthe
circuit
is
not
operating
correctly
.
A
voltage
drop
test
will
help
to
pinpoint
a
corroded
ground
strap
or
a
faulty
switch
.
Normally,
there
should
be
less
than
1
volt

drop
across
most
wires
or
closed
switches
.
A
voltage
drop
across
a
connector
or
short
cable
shouldnot
exceed
0
.5
volts
.

Voltage,
measuring

1
.
Connect
digital
multimeternegative
lead
to
a
reliable
ground
point
oncar
.

NOTE-

The
negative
(-)
battery
terminal
is
alwaysa
good
ground
point
.

2
.
Connect
digital
multimeter
positive
lead
to
point
incir-
cuit
you
wish
to
measure
.
See
Fig
.
1
.
If
a
reading
is
ob-
tained,
current
is
flowing
through
circuit
.

NOTE-

The
voltage
reading
shouldnot
deviate
more
than
1
volt
from
the
voltage
at
the
battery
.
If
the
voltage
drop
is
more
than
this,
check
for
acorroded
connector
or
cose
ground
wire
.

ELECTRICAL
TROLIBLESHOOTING

from
Battery

Fig
.
1
.



Digital
multimeterbeing
used
to
test
voltage
.

No
voltage
r_l

-1
Load

LJ

Switch

NOTE-

The
maximum
voltage
drop
in
an
automotive
circuit,
as
recommended
by
the
Society
of
AutomotiveEngineers
(SAE),
is
as
follows
:
0
voltsfor
small
vire
connections
;
0
.1
Volts
for
high
current
connections
;
0
.2
volts
for
high
current
cables
;
and
0
.3volts
for
switch
or
solenoidcon-
tacts
.
On
longer
wires
or
cables,
the
drop
may
be
slight-ly
higher
.
In
any
case,
a
voltage
drop
of
more
than
1.0volt
usually
indicates
a
problem
.

0013238

NOTE-

"
A
voltage
drop
test
is
generally
more
accuratethan
a



Voltage
drop,
testing

simple
resistance
check
because
the
resistances
in-
volvedare
often
too
small
to
measure
with
most
ohm-



Voltage
drop
can
only
be
checked
when
current
is
running
meters
.
For
example,
a
resistance
as
small
as0
.02



through
the
circuit,
suchasby
operating
the
starter
motor
or
ohms
would
results
in
a
3
volt
drop
in
a
typical
150



turning
onthe
headlights
.
A
digital
multimeter
should
beused
amp
starter
circuit
.
(150
amps
x
0
.02
ohms
=3
volts)
.



lo
ensure
accurate
readings
.

"
Keep
in
mind
that
voltage
with
the
key
on
and
voltage
with
the
engine
running
arenotthe
same
.
With
the
ig-



1
.
Connect
digital
multimeter
positive
lead
to
positive
(+)
nition
on
and
the
engine
off
(battery
voltage),
voltage



battery
terminalor
a
positive
power
supply
close
lo
bat
should
be
approximately
12
.6volts
.
With
the
engine



tery
source
.
running
(charging
voltage),
voltage
should
be
approx-
imately
14
.0
volts
.
Measure
voltage
at
the
battery
with



2
.
Connect
digital
multimeter
negativelead
to
other
end
of
the
ignition
on
and
then
with
the
engine
running
to
get



cable
orswitch
being
tested
.
See
Fig
.
2
.
exact
measurements
.

3
.
With
power
on
and
circuit
working,
meter
shows
volt-
age
drop
(difference
between
two
points)
.
This
value
should
not
exceed
1
volt
.

Continuity,
checking
Short
Circuits

from
Battery

CAUTION-

Use
only
a
high
quality
digital
ohmmeter
having
high
input
impedance
when
checking
electronic
componente
.
The
internal
power
source
used
in
most
analog
(swing-need1e)
meterscan
damage
solidstate
components
.

0013239

Fig
.
2
.



Digital
multimeter
being
used
to
check
for
voltage
drop
across
a
switch
.

The
continuity
test
can
beused
to
check
a
circuit
or
switch
.
Because
most
automotive
circuits
are
designed
to
have
little

or
no
resistance,
a
circuit
or
part
of
a
circuit
canbe
easily

checked
for
faults
using
an
ohmmeter
.
An
open
circuit
or
a
cir-

cuit
withhigh
resistance
will
not
allow
current
to
flow
.
A
círcuit
with
little
or
no
resistanceallows
current
to
flow
easily
.

When
checking
continuity,
the
ignition
should
be
off
.
On
cir-
cuits
that
are
powered
at
all
times,
the
battery
should
be
dis-
connected
.
Using
the
appropriate
wiring
diagram,
a
circuit
can
be
easily
tested
for
faulty
connections,
wires,
switches,
relays,
and
engine
sensorsby
checking
forcontinuity
.
For
a
continu-
ity
check
on
a
brake
light
switch,
see
Fig
.
3
..

A
short
circuit
is
exactly
what
the
narre
implies
.
The
circuit
takes
a
shorter
paththan
it
was
designed
to
take
.
The
most

common
short
that
causes
problems
is
a
short
to
ground

where
the
insulation
on
a
positive
(+)
wire
wears
away
and
the

metal
wire
is
exposed
.
When
the
wire
rubs
against
a
metal

partof
thecar
or
other
ground
source,
the
circuit
is
shorted
to
ground
.
If
the
exposed
wire
is
live
(positive
battery
voltage),
a

Puse
will
blow
and
the
circuit
may
possibly
be
damaged
.

ELECTRICAL
SYSTEM
-
GENERAL
600-
5

Brake
light
switch

Brake
pedal
in
rest
position

Q

Brake
pedal
depressed
Brake
light
switch

Fig
.
3
.



Brake
light
switchbeing
tested
for
continuity
.
With
brake
ped-
alin
rest
position
(switch
open)
there
is
no
continuity
(infinite
ohms)
.
With
pedal
depressed
(switch
closed)
there
is
continu-
ity
(zero
ohms)
.

Shorts
to
groundcanbe
located
with
a
digital
multimeter
.
Short
circuits
are
often
difficult
to
locate
and
may
vary
in
na-
ture
.
Short
circuits
can
befound
using
a
logical
approach
based
onthe
current
path
.

CAUTION
-

"
On
circuits
protected
with
high
rating
fuses
(25
amp
and
greater),
the
wires
or
circuit
compo-
nents
may
be
damaged
before
the
fuse
blows
.
Always
check
for
damage
before
replacing
fuses
of
this
rating
.

"
When
replacing
blown
fuses,
use
only
fuses
hav-
ingthe
correct
rating
.
Always
confirm
the
correct
fuse
rating
printed
on
the
fuselrelay
panelcover

DC

ELECTRICAL
TROUBLESHOOTING