Ground connections BMW M3 1995 E36 User Guide

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

GENERAL

This
section
contains
wiring
diagrams
for
1992
through

1998
BMW
3
Series
models
.

WARNING
-

On
cars
equipped
with
airbags,
special
precautions
apply
to
any
electrical
testing
or
repair
.
The
airbag
unit
is
an
explosive
device
and
must
be
handled
with
exterme
care
.
Before
starting
any
work
onan
airbag
equipped
car,
refer
to
the
warnings
and
cau-
tions
in
720
Seatbelts
and
721
Airbag
Systems
(SRS)
.

NOTE-

The
"



gear
position/neutral
safetyswitch
is
also
some-
timesreferred
to
as
the
automatic
transmission
range
switch
.

"
The
EWS
11
system
is
also
sometimes
referred
to
as
the
Driveaway
Protection
System
or
the
electronic
im-
mobilization
system
.

ELECTRICAL
WIRING
DIAGRAMS



ELE-1

Electrical
Wiring
Diagrams

GENERAL
.
.
.
.
.
.
.
.
.
................
.
.
.
ELE-1



Horns



.....
.
.....
.
.
.
....
.
.
.
.
.
...
.
.
ELE-153

Instrument
Panel
.
.
.
.
.
.
..............
ELE-165

ELECTRICAL
WIRING
DIAGRAMS
...
.
.
.
ELE-2



Interior
Lights/Illumination
.............
ELE-211

ABS



..............
.
.
.
.....
.
.....
ELE-117



Lumbar
Control
.
....................
ELE-247

ABS/AST
.............
.
.
.
...
.
.
.
.....
ELE-120



On-Board
Computer
..................
ELE-173

Airbag
(Supplemental
Restraint
System)
..
ELE-140



Park
Ventilation
.
.
.
...........
.
...
.
..
ELE-139

Air
Conditioning
and
Heating
.
.
.
.
.
.
.....
ELE-129



Power
Distribution
......
.
...
.
.
.
.
.
.
.
...
.
ELE-2

Anti-Theft
(Alpine)
..........
.
.
.
...
.
...
ELE-144



Power
Door
Locks
.
.
......
.
.
.
.
.
.
.
.
.
..
ELE-226

Anti-Theft
(EWS
II)
.
........
.
.
.
...
.
...
ELE-150



Power
Mirrors
...
.
.
.
......
.
.
.
.
.
.
.
.
.
..
ELE-241

Body
Computer
Module
.....
.
.....
.
...
ELE-176



Power
Seats
......
.
......
.
.
.
...
.
.
.
..
ELE-243

Charging
System



.
.
................
.
.
.
ELE-67



Power
Sunroof
.
.
.
.
.
.
.
...............
ELE-248

Convertible
Top
.
.
.
.
................
.
.
ELE-253



Power
Windows
.
.
.
.
.
.
.....
.
.........
ELE-231

Cruise
Control
..
.
.
.
...........
.
....
.
.
ELE-112



Radio/Cassette/CD/Speakers
..........
ELE-255

Data
Link
Connector
................
.
.
.
ELE-86



Rear
Window
Defogger
...............
ELE-160

Engine
Cooling
.......
.
.......
.
....
.
.
.
ELE-94



Shift
Interlock
.
.
.
.
.
.
.
.
...............
ELE-110

Engine
Management
...
.
.......
.
....
.
.
.
ELE-70



Starting
....
.
.
.
.
.
...
.
................
ELE-63

Exterior
Lights
........
.
.
.
.
.
.
.
.
.
......
ELE-194



Transmission
Electronics
.
..............
ELE-96
Ground
Distribution
....
.
.
.
.
.
.
.
.
.
.......
ELE-35



Warning
System
:
Chimes
.............
ELE-178

Headlights/Foglights
...
.
.
.
.
.
.
.
.
.
......
ELE-180



Wiper/Washer
.
.....
.
...............
ELE-155

Heated
Seats
........
.
.
.
.
.
.
.
.
.
......
ELE-245

ELECTRICAL
COMPONENT
LOCATIONS

Relayand
fuse
positions,
ground
locations
...........
.
.
.
.
.
.
.
.
.
................
seeRepair
Group
610

CAUTION-

Always
switchthe
ignition
off
and
disconnect
the
negative
(-)
battery
cablebefore
removing
any
electrical
components
.

"
Prior
to
disconnecting
the
battery,
read
the
bat-tery
disconnection
cautions
given
at
the
front
of
this
manual
on
page
viii
.

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

-Always
switch
a
test
meter
to
the
appropiate
func-
tion
and
range
before
making
test
connections
.

"
All-Season
Traction
(AST)
is
also
referred
to
as
ASC
or
ASC+T
.

GENERAL

WARNING

Your
common
sense,
good
judge-
ment,
and
general
alertness
are
cru-
cial
to
safe
and
successful
service
work
.
Befcre
attempting
any
work
on
your
BMW,
read
the
warnings
and
cautions
on
page
vi¡
and
the
copyright
page
at
the
frontof
the
manual
.
Review
these
warnings
and
cautions
each
time
you
prepare
to
workon

your
BMW
.
Please
also
read
any
warnings
and
cautions
that
accom-
pany
the
procedures
in
the
manual
.

Door
glass
See
Door
windows
Door
windows
general
information
512-1
front
door
window
(2-door
models)
adjusting
512-7
removing/installing
512-5
front
door
window
(4-door
models)
initíalizing
512-1
removing/installing
512-2
rear
door
window
(4-door
models)
removing/installing
512-4
fixed
glass,
removing/installing
512-
4
rear
vent
window
or
vent
latch,
replacing
(2-door
models)
512-11
window
regulator
and
motor,
removing/installing
512-12
window
regulator
service
512-12Doorcheck
See
DoorsDoor
handle
See
Centrallocking
and
anti-theft
Door
panel
See
Doors
Doors
general
information
411-1
door
adjustment
411-2door
check,
replacing
411-2
door
panels
411-3
doors411-1
front
orrear
door,removing/installing
411-1
front
door
panel,
removing/installing

411-3
rear
door
panel,
removing/installing
411-4
rearsidepanel,
removing/installing
(two-door
model)
411-4
Drive
axle
See
Rear
suspension
Driveability
troubleshooting

See
Engine-general
Driveshaft
general
information
260-1
center
bearing
assembly,
replacing
260-6
driveshaft,
aligning
260-3
driveshaft,
installing
260-4

Driveshaft
(cont
.)
driveshaft,
removing260-4
driveshaftservice
260-3
flex-disc,
replacing
260-5
front
centering
guide,
replacing
260-7
guibo
See
flex-disc
troubleshooting260-1

ECM
(engine
control
module)
pin
assignment
See
Fuel
injection
Electrical
circuit
See
Electrical
system-general
Electrical
component
locations
general
information
610-1
auxíliary
relay
panel
610-2
component
location
table
610-9
component
locations
610-3
fuse
position
tables
610-19
fuse
positions
610-1
relay
positions
610-2
splice
panel,
left
610-2
splice
panel,
right
610-3
Electrical
system-general
general
information
600-1
continuity,
checking
600-5
electrical
test
equipment
600-2
safety
precautions
600-1

short
circuits
600-5
short
circuit,
testing
with
ohmmeter
600-6
short
circuit,
testing
with
voltmeter
600-6
troubleshooting
600-3
voltage,
measuring600-4
voltage
and
polarity
600-1
voltage
and
voltage
drops
600-4
voltage
drop,
testing
600-4
wiring
codes
and
abbreviations
600-2
wiring
diagrams
600-2
wiring,
fuses
and
relays
600-1
Electrical
wiring
diagrams
general
information
ELE-1
wiring
diagrams
ELE-2
ABS
ELE-117

ABS/AST
ELE-120
airbag
(supplemental
restraint
system)
ELE-140
air
conditioning
and
heating
ELE-
129
anti-theft
(Alpine)
system
ELE-144
anti-theft
(EWS
II)
ELE-150
body
computer
module
ELE-176
charging
system
ELE-67
convertible
top
ELE-253
cruise
control
ELE-112
data
link
connector
ELE-86
engine
cooling
ELE-94
engine
management
ELE-70
exterior
lights
ELE-194
ground
distribution
ELE-35

headlights/foglights
ELE-180

INDEX
3

Electrical
wiring
diagrams
(cont
.)

heated
seats
ELE-245

horns
ELE-153
instrument
panel
ELE-165
interior
lights/illumination
ELE-211
lumbar
control
ELE-247
on-board
computer
ELE-173
park
ventilation
ELE-139
power
distribution
ELE-2
power
door
locks
ELE-226
power
mirrors
ELE-241
power
seats
ELE-243

power
sunroof
ELE-248

power
windows
ELE-231
radio/cassette/CD/speakers
ELE-
255
rear
window
defogger
ELE-160
shift
interlock
ELE-110
starting
ELE-63
transmission
electronics
ELE-96
warning
systems`
.
chimes
ELE-178
wiper/washer
ELE-154
Emergencies
See
Fundamentals
for
the
do-it-
yourself
owner
Engine-general
general
information
100-1
air
flow
measurement
and
vacuum
leaks
100-12
basic
engine
settings
100-11
basic
requirements
100-11
battery
voltage
100-12connecting
rods
and
pistons
100-1
cooling
system
100-5
cylinder
block
and
crankshaft100-1
cylinder
compression,
checking
100-6
cylinder
head
and
valvetrain
100-2
DISA
(dual
resonance
intake
system)
100-3,130-3
driveability
troubleshooting
100-8
engine
management
system
100-3
fuel
delivery
100-5
fuel
supply
100-14ground
connections
100-13
ignition
100-5
lubrication
system100-5
mechanical
troubleshooting
100-5
on-board
diagnostics
(OBD)
100-8
oxygen
sensors
100-11
preventive
maintenance
100-11
VANOS
(variable
valve
timing)
100-2warningsand
cautions
100-5
wiring
andharness
connections100-
13Engine
control
module
(ECM)
See
Fuel
injection
Engine
removal
and
installation
general
information
110-1
engine,
removing/installing(4-cylinder
engines)
110-1
engine,
removing/installing
(6-cylinder
engines)
110-4
Engine
coolant
temperature
(ECT)
sensor
See
Fuel
injection
Engine
hood
See
Fenders,
enginehood