Page 9 of 3342
![SUBARU LEGACY 1997 Service Repair Manual
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,
re SUBARU LEGACY 1997 Service Repair Manual
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,
re](/manual-img/17/57434/w960_57434-8.png)
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
Page 10 of 3342
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
Page 11 of 3342
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
Page 12 of 3342
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
Page 13 of 3342
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
Page 14 of 3342
4-4
[M13-6l
BRAKES
13
.
Anti-lock
Brake
System
(
AB
S)
[5.3
i
Type]
6
.
ABS
CONTROL
CYCLE
CURVES
Refer
to
4-4
[M8-6]
-*1
7
.
ABS
WARNING
LIGHT
Refer
to
4-4
[M8-7]
-*1
S
.
G
SENSOR
Refer
to
4-4
[M12-8]
.*5
12
Page 15 of 3342
4-4
[ciooi1
COMPONENT
PARTS
10
.
ABS
System
(ABS
5
.3i
Type)
10
.
ABS
System
(ABS
5
.31
Type)
1
.
SENSOR
3
so
2
T2T2
T2
T1
~
T2T2
`>
I
43
~
t
T2
T2
o
Kow
6
T
.l
o
T2
o
T2
3
B4M
1219A
D
G
sensor
(AWD
only)
~2
Rear
ABS
sensor
RH
~3
ABS
spacer
~4
Rear
ABS
sensor
LH
~5
Front
ABS
sensor
LH
~6
Front
ABS
sensor
RH
Tightening
torque
:
N~m
(kg-m,
ft-1b)
TI
:
7
.4
12
.0
boas
f
0
.2,
5
.4
f
1
.4)
T2
:
32
±
10
(3
.3
f
1
.0,
24
±
7)
2
Page 16 of 3342

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"
.