fluid SUBARU LEGACY 1997 Service Repair Manual

4-4
LM13-1]
BRAKES
13
.
Anti-lock
Brake
System
(ABS)
[5
.3i
Type]

13
.
Anti-lock
Brake
System
(ABS)
[5
.3i
Type]

1
.
FEATURE

*
This
ABS
5
.3i
type
incorporates
the
hydraulic
control
unit,
ABS
control
module,
valve
relay
and

motor
relay
in
one
unit
for
betterproductivity
and
lightweight
.

*
The
ABS
(Anti-lock
brake
system)
electrically
controls
brake
fluid
pressure
to
prevent
wheel

"lock"
during
braking
on
slippery
road
surfaces,
thereby
improving
directional/steering
stability
as

well
as
shortening
the
braking
distance
.

*
If
the
ABS
becomes
inoperative,
the
fail-safe
system
activates
to
ensure
it
acts
asa
conventional

brake
system
.
The
warning
light
also
comes
on
to
indicate
that
the
ABS
is
malfunctioning
.

"
The
front-and-rear
wheels
utilize
a
4-sensor,
4-channel
control
design
:
the
front
wheels
havean

independent
control
design*1
and
the
rear
wheels
have
a
select
low
control
design*2
.

*1
:
A
system
which
independently
controls
fluid
pressure
to
left
and
right
front
wheels
.

*2
:
A
system
which
provides
the
same
fluid
pressure
control
for
the
two
rear
wheels
if
either
wheel

starts
to"lock
."

10
ABS
control
moduleand
hydraulic
control
unit
(ABSCM&H/U)
Proportioning
valve
OO
Diagnosisconnector
OO
ABS
warning
light

OO
Data
link
connector
(for
SUBARU
select
monitor)
OO
Transmission
control
module
(only
AT
vehicle)
Tone
wheel

OO
ABS
sensor
09
Wheel
cylinder
O
G
sensor
(only
AWD
vehicle)
>>
Brake
switch
D
Master
cylinder

?15A

2

BRAKES
IM13-21
4-4
13
.
Anti-lock
Brake
System
(ABS)
[5
.3i
Type]

2
.
FUNCTIONS
OF
SENSORS
AND
ACTUATORS

Name
Function

ABS
control
moduleand
hydraulic
ABSCM-
e
Calculates
and
determine
the
conditionsof
the
wheels
and
body
from
control
unit
(ABSCM&H/U)
section
the
wheel
speedsand
makes
a
proper
decision
suitable
for
the
current
situation
to
control
the
hydraulic
unit
.

In
the
ABS
operation
mode,
the
module
outputs
a
cooperative
control
signal
to
the
AT
control
module
.
(AT
vehicles
only)

Whenever
the
ignition
switch
is
placed
at
ON,
the
module
makes
a
self
diagnosis
.
When
anything
wrong
is
detected,
the
module
cuts
off
the
system
.

Communicates
with
the
Subaru
select
monitor
.

H/U-section
In
the
ABS
operation
mode,
the
H/U
changes
fluid
passages
to
control

the
fluid
pressure
of
the
wheel
cylinders
in
response
to
an
instruction
from
the
ABSCM
.

The
H/U
also
constitutes
thebrake
fluid
passage
from
the
master
cylin-
der
to
the
wheel
cylinders
together
with
pipings
.

Valve
relay-
Serves
asa
power
switch
for
the
solenoid
valve
and
motor
relay
coil
in
section
response
to
an
instruction
from
the
ABSCM
.

Motor
relay-
Serves
as
a
power
switch
for
the
pump
motor
in
response
to
an
instruc-
section
tion
from
the
ABSCM
.

Wheel
speed
sensor
(ABS
sensor)
Detects
the
wheel
speed
in
terms
of
a
change
in
the
magnetic
flux
den-
sity
passingthrough
the
sensor,
converts
it
into
an
electrical
signal,
and
outputs
the
electrical
signal
to
the
ABSCM
.

Tone
wheel
Gives
a
change
in
the
magnetic
flux
density
by
the
teeth
around
the
tone
wheel
to
let
the
ABS
sensor
generate
an
electrical
signal
.

G
sensor
(AWD
vehicle
only)
Detects
a
change
in
G
in
the
longitudinal
direction
of
the
vehicle
and
outputs
it
to
the
ABSCM
in
terms
of
a
change
in
voltage
.

Stop
light
switch
Transmits
the
information
on
whether
the
brakepedal
is
depressed
or
not
to
the
ABSCM
for
use
as
a
condition
in
determining
ABS
operation
.

ABS
warning
light
Alerts
the
driver
to
an
ABS
fault
.
When
the
diagnosis
connector
and
diagnosis
terminal
are
connected,
the
light
flashes
to
indicate
a
trouble
codes
in
response
to
an
instruction
from
the
ABSCM
.

AT
control
module
(TCM)
(AT
vehicles
only)
Provides
shift
controls
(fixing
the
speed
at
3rd
or
changing
front
and
rear
wheel
transmission
characteristics
on
4WD
vehicle)
in
response
to
an
instruction
fromthe
ABSCM
.

4-4
[M13-51
BRAKES
13
.
Anti-lock
Brake
System
(ABS)
[5
.3i
Type]

5
.
ABSCONTROLMODULEAND
HYDRAULIC
CONTROL
UNIT
(ABSCM&H/U)

*
ABS
CONTROL
MODULE
SECTION
(ABSCM)

The
ABSCM
is
a
digital
control
type
electronic
control
module
accommodating
two
microcontrol

modules
(MCMs)
;
master
and
slave
.
Both
MCMs
process
the
same
program
and
monitor
the

respective
outputs,
and
when
a
mismatch
occurs,
cut
off
the
system
to
activate
the
fail-safe
func-

tion
.

A
maximum
of
3
trouble
codes
are
stored
in
the
EEP
ROM
and
if
3or
more
areas
fail,
then
only
the

3
most
recent
failures
are
stored
.
The
trouble
codes
remain
stored
until
they
are
erased
.

This
ABSCM
inducesa
sequence
control
pattern
and
facilitates
the
checking
of
the
hydraulic
unit
.

"
ABS
control

Based
on
the
four
wheel
speed
signals,
the
ABSCM
calculates
a
simulated
body
speed
or
body

deceleration
rate,
whilereferencing
the
G
sensor
output
asan
auxiliary
means,
and
compares
them
with
the
wheel
speeds
and
wheel
deceleration
rates
.
If
it
determines
that
the
wheels
are

about
to
lock,
it
controls
the
solenoidvalve
or
motor
pump
of
the
H/U
to
adjustthe
brake
fluid
pres-

sures
that
act
on
the
wheel
cylinders,
thereby
preventing
the
wheels
from
locking
.

The
ABSCM
controls
the
right
and
left
front
wheel
fluid
pressures
independently
and
controls
the

rear
wheel
fluid
pressures
on
the
basis
of
the
wheel
which
is
more
likely
to
lock
(Select-low
control)
.

"
Select
monitor
associated
functions

The
Subaru
select
monitor
may
beused
to
perform
the
following
operations
.

O
To
read
out
analogdata
Toread
out
ON/OFF
data

O
Toread
out
or
erase
trouble
code

O
Toread
out
status
information
in
the
event
of
trouble
(Freeze
frame
data)

O
To
initiate
ABS
sequence
control
pattern

"
Indication
functions

The
ABS
warning
light
can
be
made
to
indicate
the
following
three
states
.

O
ABS
trouble

Flashes
to
indicate
trouble
codes
in
diagnosis
mode
.

O
Valve
ON/OFF
when
sequence
control
pattern
isin
effect

6

BRAKES
[M13-5]
4-413
.
Anti-lock
Brake
System
(AB
S)
[
5
.3i
Typ
e]

"
HYDRAULIC
CONTROL
UNIT
SECTION
(H/U)

The
H/U
is
a
fluid
pressure
controller
comprising
a
motor,
solenoid
valve,
housing,
relay,
etc
.
It

constitutes
two
diagonally
independent
brake
fluid
circuits
for
a
cross
piping
vehicle
.

"
The
pump
motor
rotates
an
eccentric
cam
to
let
the
plunger
pump
generatea
hydraulicpres-

sure
.

"
The
housing
accommodates
the
pump
motor,
solenoid
valve,
reservoir,
etc
.,
and
also
consti-
tutes
abrake
fluid
passage
.

"
The
plunger
pump
is
a
hydraulic
pump
which
drains
off
the
brake
fluid
which,
when
the
pressure

is
reduced,
is
discharged
to
the
reservoir,
and
sends
it
toward
the
master
cylinder
.

"
The
solenoid
valve
is
a
2-position
type
solenoidvalve
which
switches
the
brake
fluid
passages

between
the
wheel
and
master
cylinder
and
reservoir
sides
in
response
to
an
instruction
from
the

ABSCM
.

For
each
wheel
cylinder,
a
pairof
normally-closed
and
-opened
solenoid
valves
are
provided
.

*
The
inlet
solenoid
valve
is
duty-controlled
to
reduce
brake
fluid
pulsation
for
IowerABS
operation

noise
.

"
The
reservoir
is
a
fluid
chamber
which
temporarily
storesthe
brake
fluid
to
be
discharged
from

the
wheel
cylinder
when
the
pressure
is
reduced
.

"
The
damper
chamber
suppresses
thepulsation
of
the
brake
fluid
which,
when
the
pressure
is

reduced,
is
discharged
from
the
plunger
pump,
thereby
minimizing
the
kickbacks
to
the
brake

pedal
.

*
The
valve
relay
controls
the
solenoid
valve
and
motor
relay
energizing
power
supply
in
response

to
an
instruction
from
the
ABSCM
.
In
normal
(1G
ON)
condition,
the
relay
is
actuated
to
supply

power
to
the
solenoid
valve
and
motor
relay
.
When
an
error
occurs
in
the
system,
the
valve
relay

is
forced
to
OFF
to
keep
the
fluid
pressure
circuit
in
the
normal
mode
(normal
brake
mode)
and

also
constitute
the
ABS
warning
light
operating
circuit
.

"
The
motor
relay
supplies
power
to
the
pump
motor
to
operate
the
plunger
pump
in
response
to

an
instruction
from
the
ABSCM
in
the
ABS
control
mode
.

TheH/U
has
four
operating
modes
;
normal
mode
(control
OFF
:
normalbrake
mode),
"increase",

"hold"
and
"decrease"
modes
(control
ON
in
all
the
three
modes)
.

7

4-4
[M13-51
BRAKES
13
.
Anti-lock
Brake
System
(ABS)
[5
.3i
Type]

1)
During
normal
braking(Explained
with
one
wheel's
control
asan
example)

Since
no
current
is
supplied
to
the
inlet
and
outlet
solenoid
valves,
no
solenoid
valve
attracting

force
is
generated
.
So
thevalves
remain
stationary
.

Accordingly,
the
inlet
port
of
the
inlet
solenoid
valve
isin
an
opened
state,
whereas
the
outlet
port

of
the
outlet
solenoidvalve
isin
a
closed
state
.
So
the
fluid
pressure
of
the
master
cylinder
is
trans-

mitted
to
the
wheel
cylinder
to
produce
abrake
force
in
the
wheel
cylinder
.

From
master
cylinder

v

N

Du

Reservoir

B4H0989

BRAKES
[M13-5]
4-413
.
Anti-lock
Brake
System
(ABS)
[5
.3i
Type]

2)
Pressure
"decrease"
action
with
ABS
in
operation(Explained
with
one
wheel's
control

as
anexample)

Current
is
supplied
to
the
inlet
and
outlet
solenoid
valves,
and
the
generated
solenoid
valve
attract-

ing
forces
close
the
inlet
port
and
open
the
outlet
port
.

Accordingly,
the
wheel
cylinder
is
isolated
from
the
master
cylinder
and
becomes
clear
to
the
res-

ervoir,
allowing
the
brake
fluid
to
flow
to
the
reservoir
.
So
the
fluid
pressure
of
the
wheel
cylinder

is
decreased
.

The
brake
fluid
collected
in
the
reservoir
is
fed
to
the
master
cylinder
by
the
pump
.

From
master
cylinder
\/
\/

Reservoir

B4H0990

9

4-4
IM13-5]
BRAKES
13
.
Anti-lock
Brake
System
(ABS)
[5
.3i
Type]

3)
Pressure
"hold"
action
with
ABS
in
operation
(Explained
with
one
wheel's
control
asan

example)

Current
is
supplied
to
the
inlet
solenoid
valve,
and
the
generated
solenoid
valve
attracting
force

closes
the
inlet
port
.

Sinceno
current
is
supplied
to
the
outlet
solenoid
valve,
the
output
port
remains
in
a
closed
state
.

As
a
result,
the
wheel
cylinder,
master
cylinder
and
reservoir
are
blocked,
and
the
fluid
pressure

of
the
wheel
cylinder
is
maintained
constant
.

During
ABS
operation,the
pump
motor
continues
to
operate
.

From
master
cylinder
N~

O

Reservoir

B4H0991

10

BRAKES
[M13-5]
4-4
13
.
Anti-lock
Brake
System
(ABS)
[5
.3i
Type]

4)
Pressure
"increase"
action
with
ABS
in
operation(Explained
with
one
wheel's
control
as
anexample)

Since
no
current
is
supplied
to
the
inlet
and
outlet
solenoid
valves,
no
solenoidvalve
attracting

force
is
generated
.
So
the
valves
remain
stationary
.

Accordingly,
the
inlet
port
of
the
inlet
solenoid
valve
isin
an
opened
state,
whereas
the
outlet
port

of
the
outlet
solenoid
valve
is
in
a
closed
state
.
So
the
fluid
pressure
of
the
master
cylinder
is
trans-

mitted
to
the
wheel
cylinder
to
increase
the
brake
force
in
the
wheel
cylinder
.

During
ABS
operation,
the
pump
motor
continues
to
operate
.

From
master
cylinder
\
V

Reservoir

B4H0992

11

BRAKES
44

Page

S
SPECIFICATIONS
AND
SERVICE
DATA

1
.
Brakes

C
COMPONENT
PARTS
...........
.
.
.
.....................
.
.
......
..
.
.
.
..........................

1
.
FrontDisc
Brake

2
.
Rear
Disc
Brake

3
.
Rear
Drum
Brake

4
.
Master
Cylinder

5
.
Brake
Booster

6
.
ABS
System
7
.
Hill
Holder

8
.
Parking
(Hand)
Brake
9
.
ABS/TCS
System

10
.
ABS
System(ABS
5
.3i
Type)
...
....
.
...
..........................
.
.
...
.
.............

W
SERVICE
PROCEDURE
...............
.
.
......
.
.
...
.
....................
.
.
.
.
.
.
...
.
...
.
.......

1
.
Front
Disc
Brake
2
.
Rear
Disc
Brake

3
.
Rear
Drum
Brake
4
.
Parking
Brake
(Rear
Disc
Brake)
5
.
Master
Cylinder

6
.
Brake
Booster

7
.
Brake
Hose
8
.
Hill
Holder

9
.
Parking
Brake
Lever

10
.
Parking
Brake
Cable

11
.
Air
Bleeding
(Without
TCS
model)

12
.
Brake
Fluid
Replacement

13
.
Proportioning
Valve

14
.
ABS
Sensor

15
.
Hydraulic
Unit
for
ABS
System

16
.
ABS
Control
Module

17
.
G
Sensor
for
ABS
System

18
.
Brake
Hose
and
Pipe
am
.
.
.....
.
.................................
.
.
...
.
.....
..

19
.
Air
Bleeding
(With
TCS
model)

20
.
Hydraulic
Unit
for
ABS/TCS
System

21
.
ABS/TCS
Control
Module

22
.
Hydraulic
Unit
for
ABS
System
(ABS
5
.3
Type)

23
.
ABS
Control
Module
(ABS
5
.3
Type)

24
.
G
Sensor
for
ABS
System
(ABS
5
.3
Type)

25
.
ABS
Control
Module
and
Hydraulic
Control
Unit
(ABSCM&H/U)
[ABS
5
.3i
Type]
.
.
.
.
.
.
.
...
.
.
.
.
.
..
.
.
...................................
.
...
.
.
.........
..........
26
.
ABS
Sensor
(ABS
5
.3i
Type)
....
...........................................
.
.
....
.
...
.
27
G
Sensor
(ABS
5
3i
T
e)

2

....
.2

....
.4

........
.
.
..
.4

....
..
.15

....
..
.15
yp
....
.
.
......
...
.
...................................
.
.
.
.
.......
.
.
.....

K
DIAGNOSTICS

1
.
Entire
BrakeSystem

2
.
Hill
Holder

PRECAUTION
FORSUPPLEMENTAL
RESTRAINT
SYSTEM
"AIRBAG"
The
Supplemental
Restraint
System
"Airbag"
helps
to
reduce
the
risk
or
severity
of
injury
to
the
driver
in
a
frontal
collision
.
The
Supplemental
Restraint
System
consists
of
an
airbag
module
(located
in
the
center
of
the
steer-
ing
wheel),sensors,
a
control
module,warning
light,
wiring
harness
and
roll
connector
.
Information
necessary
to
servicethe
safety
is
included
in
the"5-5
.
SUPPLEMENTAL
RESTRAINT
SYSTEM"
ofthis
Service
Manual
.
WARNING
:
"
To
avoid
rendering
the
Airbag
system
inoperative,
which
could
lead
to
personal
injury
or
death
in
the
event
of
a
severe
frontal
collision,
all
maintenance
must
be
performed
byan
authorized
SUBARU
dealer
.
"
Improper
maintenance,
including
incorrect
removal
and
installation
of
the
Airbag
system,
can
lead
to
personal
injury
caused
by
unintentional
activation
of
the
Airbag
system
.
"
All
Airbag
system
electrical
wiring
harnesses
and
connectors
are
covered
with
yellow
outer
insu-
lation
.
Do
not
use
electrical
test
equipment
on
any
circuit
relatedtothe
Supplemental
Restraint
System
"Airbag"
.

SERVICE
PROCEDURE
[w2sao1
4-4

25
.
ABS
Control
Module
and
Hydraulic
Control
Unit
(ABSCM&H/U)
[ABS
5
.3i
Type]

A
:
REMOVAL

1)
Disconnect
ground
cablefrom
battery
.

2)
Remove
air
intake
duct
fromengine
compartment
to

facilitate
removal
of
ABSCM&H/U
.

3)
Use
an
air-gun
to
get
rid
of
water
around
the

ABSCM&H/U
.

CAUTION
:

The
contact
will
be
insufficient
if
the
terminal
gets
wet
.

4)
Pull
on
the
lock
of
the
ABSCM&H/U
connector
to

remove
it
.

5)
Disconnect
connector
from
ABSCM&H/U
.

CAUTION
:

Be
careful
not
tolet
water
or
other
foreign
matter
con-

tact
the
ABSCM&H/U
terminal

6)
Unlock
cable
clip
.

7)
Disconnect
brake
pipes
from
ABSCM&H/U
.

CAUTION
:

Wrap
brake
pipes
with
vinyl
bag
to
avoid
spilling
brake

fluid
on
vehicle
body
.

8)
Remove
ABSCM&H/U
fromengine
compartment
.

CAUTION
:

9
ABSCM&H/U
cannotbe
disassembled
.
Do
not
attempt

to
loosen
bolts
and
nuts
.

"
Do
not
drop
or
bump
ABSCM&H/U
.

"
Do
not
turn
the
ABSCM&H/U
upside
down
or
place
it

on
its
side
.

*
Be
careful
to
prevent
foreign
particles
from
getting

into
ABSCM&H/U
.

9
Apply
acoat
of
rust-preventive
wax
(Nippeco
LT
or

GB)
to
bracket
attaching
bolt
after
tightening
.

*
Do
not
pull
harness
disconnecting
harness
connector
.

7