1992 BMW 325i ELECTRICAL WIRING

GENERAL

This
repair
group
covers
trunk
lid
removal
and
installation
.

Also
inciuded
here
arereplacement
procedures
for
the
gas-
charged
support
struts
that
hold
the
trunk
lid
in
the
up
position
.

NOTE
-

The
body
ís
painted
at
the
factory
after
assembly
.
Re-
alignment
of
body
panels
may
expose
unpainted
metal
.
Paint
all
exposed
metal
once
the
work
is
complete
.

TRUNK
LID
Trunk
lid,
removing
and
installing

1
.
Raise
trunk
lid
.
Open
tool
kit
and
remove
screws
at-

taching
tool
kit
lo
trunk
lid
.

2
.
Remove
insulating
liner
from
underside
of
trunk
lid
.
See

Fig
.
1
.

412
Trunk
Lid

TRUNK
LID



412-1

GENERAL
............
.
...
.
.....
.
...
.
.
412-1



Trunk
lid,
aligning
.
.
.
.
.
.....
.
...
.
.
.
.
.
.
.
..
412-2
Trunk
lid
support
strut,

TRUNK
LID
.
.
.
............
.
.
.
...
.
.
.
.
.
.
412-1



removing
and
installing
..
.
.
.
.
.
.
.
.
.
...
.
.
.
412-2

Trunk
lid,
removinb
and
installing
......
.
.
.
.
412-1

3
.
Disconnect
wiring
from
electrical
components
and
re-

move
complete
wiring
harness
from
trunk
lid
.

4
.
While
supporting
trunk
lid,
loosen
top
hinge
bolts
and
remove
lower
bolts
from
left
and
right
sides
.
Remove
trunk
lid
with`aid
of
helper
.
See
Fig
.
2
.

NOTE-

Before
loosening
hinge
bolts,
mark
hinge
and
hinge
bolt
locations
for
reínstallation
.

0013163

Fig
.
2
.



Trunk
lid
hinge
bolts
(arrows)
.
Loosen
upper
bolt
and
remove
lower
bolt
.

0013162



5
.
Installation
is
reverse
of
removal
.
If
necessary,
align

Fig
.
1
.



Trunk
lid
liner
retaining
screws
and
clips
(arrows)
.



trunk
lid
to
body
as
described
next
.

TRUNK
LID

515
Central
Locking
and
Anti-Theft

GENERAL
.....
.
.
.
.
.
.
.
..:
.
.
.
......
.
.
.
.
515-1



Luggage
compartment
locking
actuator,
removing
and
installing
.
.
.
.
.
...........
.
515-6

DOOR
HANDLES
AND
LOCKS
.........
515-1



LOCKING
SYSTEM
AND
Front
door
lock,
removing
and
installing
....
.515-1



ELECTRONIC
IMMOBILIZATION
......
.515-7
Front
door
handle,
removing
and
installing
...
515-3

Rear
door
lock,
removing
and
installing
.....
515-4



Central
Locking
System(ZVM)
.
.
.
.
.......
.
515-7

Rear
door
handle,
removing
and
installing
...
515-5



Central
Body
Electronics
(ZKE
IV)
.
.
.......
.515-8

Electronic
Immobilization
System
(EWS)
.
.
.
.
.515-8
Door
striker,
rep
lacing
.
.
.
.
.
.
.
.
.
..........
515-6



EWS
II
control
module,
re
lacin



515-10

LOCKING
ACTUATORS
.
.
.
.
.
.
..........
515-6



Ring
antenna,
replacing
.
.
.
.
.
.
.
.
.
.
...
.
.
.
.
515-10

Door
Locking
Actuator
.
.
.
.
.
.
.
.
..........
515-6



EWS
II
transmitter/receiver
module,

replacing
...........
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
515-11

GENERAL

This
section
covers
repair
information
for
the
central
locking

and
the
anti-theft
systems
.
Keep
in
mind
that
E36
cars
are



CA
UTION-

equipped
with
sophisticated
and
self-diagnostic
electrical
sys-



Prior
to
disconnecting
the
battery,
read
the
battery

tems
.
When
experiencing
malfunctions
relatinglo
the
central



disconnection
cautions
given
at
the
front
of
this

locking
or
the
anti-theft
system,
it
is
recommended
that
the



manual
onpage
vi¡¡
.

systembe
diagnosed
using
the
BMW
service
tester
(DIS)
.

This
advanced
diagnostic
tool
can
usually
pinpoint
electrical



NOTE-
faults
quickly
and
safely
.
Consult
an
authorized
BMW
dealer
.
In
some
models
covered
inthis
manual,
it
is
not
essen-
tial
to
remove
the
side-impact
airbag
to
access
intemal

NOTE-



door
components
.
However,
the
procedure
is
recom-

Additional
general
electrical
information
can
be
found



mended
for
safely
reasons
.

i
n
610
Electrical
Component
Locations
and
Electri-
cal
Wiring
Diagrams
.



4
.
Disconnect
harnessconnector
from
window
motor
to

DOOR
HANDLES
AND
LOCKS

Front
door
lock,
removing
and
installing

1
.
Remove
front
door
panel
and
vapor
barrier
asde-

scribed
in
411
Doors
.

WARNING
-

Some
1997
and
all
1998
cars
are
fitted
with
side-im-

pact
airbags
in
the
front
doors
.
When
servicing
the
door
locks
on
cars
with
front
side-impact
airbags,
al-
ways
disconnect
the
negative
(-)
battery
terminal
.
See721
Airbag
System
(SRS)
forcautions
andpro-
cedures
relating
to
the
airbag
system
.

2
.
Raise
door
window
completely

CENTRAL
LOCKING
AND
ANTI-THEFT



515-1

3
.
On
cars
with
side-impact
airbags,
disconnect
negative
(-)
cable
from
battery,
then
remove
airbag
module
.

prevent
accidental
operation
.

5
.
On
4-door
cars
:
Peel
back
rubber
window
guide
from

reas
guide
rail
:
Remove
guide
rail
mounting
boltat
bot-

tom
.
Unclip
any
wiring
from
guide
rail
and
pull
guide
rail

downward
and
remove
from
door
.
See
Fig
.
1
.

NOTE
-

The
top
of
the
guide
rail
is
"hooked"
to
the
doorsheet
metal
.

6
.
Remove
inside
door
handle
retaining
screw
.
Discon-

nect
inside
handle
from
linkage
and
remove
.
See
Fig
.

2
.

7
.
Cut
wire
ties
and
remove
door
lock
electrical
harness
con-

nector
.
Remove
door
lock
mounting
screws
.
See
Fig
.
3
.

8
.
Working
inside
door,
disconnect
outside
door
handle

and
lockcylinder
linkage
from
door
lock
.
Remove
lock

from
inside
door
.
See
Fig
.
4
.

DOOR
HANDLES
AND
LOCKS

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
.

520-2



S
EATS

Fig
.
2
.



Frontseat
front
mounting
nut
(arrow)
.

FRONT
SEA
TS

0013166

5
.
On
2-door
cars
:
unhook
seat
belt
from
guide
on
seat

back
.

8
.
Remove
seatfrom
car
.

Fig
.
3
.



Seat
belt
mounting
bolt
(arrow)
.

0013216

9
.
Installation
is
reverse
of
removal
.
Keep
the
following
in

mind
:

6
.
Tilt
seat
back
to
access
and
unplug
electrical
harness



"
Use
wire
ties
orequivalent
means
to
keep
seat
har
connectors
.
Cut
or
untwist
wire
ties
as
necessary
.



ness
wiring
from
being
exposed
to
fraying
.
"
Reactivate
front
seat
belt
locks
.
7
.
On
4-door
cars
:
Unbolt
seat
belt
from
seat
frame
.
See



"
Start
all
seat
mounting
boits
.
Fig
.
3
.



"
Tighten
seat
mounting
fasteners
in
thís
sequence
:
in-
ner
front
;
outer
front
;
inner
rear,
outer
rear
.

Tightening
Torque

"
Front
seat
to
floor



........
.......
55
Nm
(41
ft-Ib)

600
Electrical
System-General

GENERAL
.
...........
.
.
.
.
.
.
.
.
.
...
.
...
600-1

Voltage
and
Polarity
........
.
.
.
.
.
.
.
.....
600-1

Ming,
Fuses
and
Relays
............
.
.
.
.
600-1

Electrical
System
Safety
Precautions
...
.
.
.
.
600-1

Electrical
Test
Equipment
.....
.
.
.
....
.
.
.
.
600-2

WIRING
DIAGRAMS
..
.
.
.
.
.
.
.
.
.
........
600-2

Ming
Codes
and
Abbreviations
..
.
...
.
....
600-2

ELECTRICAL
TROUBLESHOOTING
..
.
..
600-3

Voltage
and
Voltage
Drops
..........
.
.
.
.
.
600-4

GENERAL



Electrical
System
Safety
Precautions

A
brief
description
of
the
principal
parts
of
the
electrical
sys-
tem
is
presented
here
.
Also
covered
here
are
basic
electrical
system
troubleshooting
tips
.

Voltage
and
Polarity

The
vehicle
electrical
system
is
a
12-volt
direct
current
(DC)
negative-ground
system
.
A
voltage
regulator
controls
system
voltage
at
approximately
the
12-volt
rating
of
the
battery
.
Al¡
circuits
are
grounded
by
direct
or
indirect
connection
to
the

negative
(-)
terminal
of
the
battery
.
A
number
of
ground
con-

nections
throughout
the
car
connect
the
wiring
harness
to

chassis
ground
.
These
circuits
are
completedby
the
battery

cable
or
ground
strap
between
the
body
and
the
battery
nega-

tive
(-)
terminal
.

Wiring,
Fuses
and
Relays

Nearly
all
parts
of
the
wiring
harnessconnect
to
compo-

nents
of
the
electrical
system
with
keyed,
push-on
connectors

that
lock
into
place
.
Notable
exceptions
arethe
heavy
battery

cables
and
the
starter
wiring
.
The
wiring
is
color-coded
for
cir-

cuitidentification
.

With
theexception
of
the
battery
charging
system,
most

electrical
power
is
routed
from
the
ignition
switch
or
the
bat-
tery
through
the
main
fuse/relay
panel,
located
in
¡he
left
rear

comer
of
the
engine
compartment
.
Fuses
are
color
coded
to

indicate
current
capacities
.

The
relays
and
control
units/modules
are
mounted
in
vari-

ous
places
throughout
the
vehicle
.
See610
Electrical
Com-

ponent
Locations
.

ELECTRICAL
SYSTEM-GENERAL
600-1

Voltage,
measuring
.
.
.
................
.
.
600-4

Voltage
drop,
testing
.
.
.....
.
.....
.
......
600-4

Continuity,
checking
..
.
...
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
600-5
Short
Circuits
.
.
.
.
.
.
.
.
.....
.
...
.
.
.
.
.
.
.
.
.
600-5

Short
circuit,
testing
with
ohmmete'r
.
.
.
.
.
.
.
.
.
600-6

Short
circuit,
testing
with
voitmeter
.
.
.
.
.
.
.
.
.
600-6

TABLES
a
.
Terminal
and
Circuit
Numbers
..............
..
.600-3
Please
read
the
following
warnings
and
cautions
before
do-
ing
any
work
on
your
electrical
system
.

WARNING
-

"
The
cars
covered
by
this
manual
are
equipped
with
aSupplemental
Restraint
System
(SRS)
that
automatically
deploys
one
or
more
airbags
.
Each
airbag
unit
houses
an
explosive
powerful
charge
.
Any
work
involving
the
SRS
system
should
only
be
performed
byan
authorized
BMW
dealer
.
Making
repairs
without
the
proper
knowledge
and
special
test
equipment
may
cause
serious
per-
sonal
injury
.
See
721
Airbag
System
(SRS)
.

"
The
ignition
system
of
the
car
operates
at
lethal
voltages
.
People
with
pacemakers
or
weak
hearts
should
not
expose
themselves
to
the
ignition
sys-
tem
.
Extra
caution
mustbe
taken
when
working
on
the
ignition
system
or
when
servicing
theen-
gine
while
it
is
runningor
the
key
is
on
.
See
120
Ignition
System
for
additional
ignition
system
warnings
and
cautions
.

"
Before
operating
the
starter
without
starting
the
engine
(as
when
making
a
compressfon
test),
dis-
able
the
ignition
system
as
described
in
120
Igni-
tion
System
.

"
Keep
hands,
clothing
and
other
objects
clear
of
the
electric
radiator
coollng
fan
when
working
on
a
warm
engine
.
The
fan
may
start
at
any
tíme,
even
when
the
ignition
is
switched
off
.

GENERAL

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

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