ESP SUBARU LEGACY 1997 Service Repair Manual

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

4-4d
[T8E14]
BRAKES
[ABS
5
.31
TYPE]
8
.
Diagnostics
Chart
with
Trouble
Code
by
ABS
Warning
Light

I

-

f
8E14
CHECK
ABSCM&H/U
.

1)
Connect
all
connectors
.

2)
Erase
the
memory
.

3)
Perform
inspection
mode
.

4)
Read
outthe
trouble
code
.

CHECK
:
Is
the
same
trouble
code
as
in
the
current

diagnosis
still
being
output?

ves
:
Replace
ABSCM&H/U
.

No
:
Go
to
step
8E15
.

I8E1
5
CHECK
ANY

IAPPEARANCE

.THER
TROUBLE
CODES

Are
other
trouble
codes
being
output?

Proceed
with
the
diagnosis
corresponding
to
the

trouble
code
.

No
:
A
temporarypoor
contact
.

NOTE
:

Check
harness

and
ABS
sensor
.

and
connectors
between
ABSCM&H/U

38

4-4d
[TSiis]
BRAKES
[ABS
5
.31
TYPE]

8
.
Diagnostics
Chart
with
Trouble
Code
by
ABS
Warning
Light

18118
1
CHECKABSCM&HIU
.

1)
Connect
all
connectors
.

2)
Erase
the
memory
.

3)
Perform
inspection
mode
.

4)
Read
out
the
trouble
code
.

CHECK
:
Is
the
same
trouble
code
as
in
the
current

diagnosis
still
being
output?

YES
:
Replace
ABSCM&H/U
.

No
:
Go
to
step8119
.

8,19
CHECK
ANY
OTHER
TROUBLE
CODES

APPEARANCE
.

CHECK
:
Are
other
trouble
codes
being
output?

,rES
:
Proceed
with
the
diagnosis
corresponding
to
the

trouble
code
.

No
:
A
temporary
noise
interference
.

46

4-4d
[TSJs1
BRAKES
[ABS
5
.31
TYPE]

8
.
Diagnostics
Chart
with
Trouble
Code
by
ABS
Warning
Light

G4M0700
I

G4M0701

CHECK
INSTALLATION
OF
TONE
WHEEL
.

Tightening
torque
:

13
f
3
N~m
(1.3
f
0
.3
kg-m,
9
f
2
.2
ft-Ib)

CHECK
:
Are
the
tone
wheel
installation
bolts
tight-

ened
securely?

,res
:
Go
to
step
8J7
.

No
:
Tightentone
wheel
installation
bolts
securely
.

8J7
I
CHECK
ABS
SENSOR
GAP
.

Measure
tone
wheel
to
pole
piece
gap
over
entire
perim-

eter
of
the
wheel
.

CHECK
:
Is
the
gap
within
thespecifications
shown
in

the
following
table?

Front
wheel
Rear
wheel

Specifications
0
.9
-
1.4
mm

(0
.035
-
0
.055
in)
0
.7
-
1.2
mm

(0
.028
-
0
.047
in)

,
.ES
:
Go
tostep
8J8
.

No
:
Adjust
the
gap
.

NOTE
:

Adjustthe
gap
using
spacer
(Part
No
.
26755AA000)
.
If

spacers
cannot
correct
the
gap,
replace
worn
sensor
or

worn
tone
wheel
.

18,18
1
CHECK
OSCILLOSCOPE
.

Is
an
oscilloscopeavailable?

YES
:
Go
to
step
8J9
.

No
:
Go
to
step
8,1110
.

8J9
I
CHECK
ABS
SENSOR
SIGNAL
.

1)
Raise
all
four
wheels
of
ground
.

2)
Turn
ignition
switch
OFF
.

3)
Connect
theoscilloscope
to
the
connector
(F1)
or
con-

nector(B100)
.

4)
Turn
ignition
switch
ON
.

50

t
Sensor
gap

Sensor
gap

4-4d[T8J13]
BRAKES
[ABS
5
.3i
TYPE]

8
.
Diagnostics
Chart
with
Trouble
Code
by
ABS
Warning
Light

8
.113
CHECK
ABSCM&H/U
.

1)
Turn
ignition
switch
to
OFF
.

2)
Connect
all
connectors
.

3)
Erase
the
memory
.

4)
Perform
inspection
mode
.

5)
Read
outthe
trouble
code
.

CHECK
:
Is
the
same
trouble
code
as
in
thecurrent

diagnosis
still
being
output?

.rES
:
Replace
ABSCM&H/U

No
:
Go
to
step
8J14
.

CHECK
ANYOTHER
TROUBLE
CODES

APPEARANCE
.

CHECK
:
Are
other
trouble
codes
being
output?

,rES
:
Proceed
with
the
diagnosis
corresponding
to
the

trouble
code
.

No
:
A
temporarypoor
contact
.

52

4-4d
R8N41
BRAKES
[ABS
5
.31
TYPE]

8
.
Diagnostics
Chart
with
Trouble
Code
by
ABS
Warning
Light

8N4
I
CHECK
ABSCM&H/U
.

1)
Connect
all
connectors
.

2)
Erase
the
memory
.

3)
Perform
inspection
mode
.

4)
Read
out
the
trouble
code
.

CHECK
:
Is
the
same
trouble
code
as
in
the
current

diagnosis
still
being
output?

Replace
ABSCM&H/U
.

No
:
Go
to
step
8N5
.

8NS
CHECK
ANY

APPEARANCE

.THER
TROUBLE
CODES

CHECK
:
Are
other
trouble
codes
being
output?

0
:
Proceed
with
the
diagnosis
corresponding
to
the

trouble
code
.

n~o
:
A
temporary
poor
contact
.

56

4-4d
[rsRaj
BRAKES
[ABS
5
.31
TYPE]
8
.
Diagnostics
Chart
with
Trouble
Code
by
ABS
Warning
Light

1
8R4
I
CHECK
ABSCM&H/U
.

1)
Connect
all
connectors
.

2)
Erase
the
memory
.

3)
Perform
inspection
mode
.

4}
Read
outthe
trouble
code
.

Is
the
same
trouble
code
as
in
thecurrent

diagnosis
still
being
output?

,rES
:
Replace
ABSCM&H/U
.

No
:
Go
to
step
81145
.

8R5
CHECK
ANY
OTHER
TROUBLE
CODES

APPEARANCE
.

Are
other
trouble
codes
being
output?

Proceed
with
the
diagnosis
corresponding
to
the

trouble
code
.

A
temporary
poor
contact
.

60

4-4d
Rsssi
BRAKES
[ABS
5
.31
TYPE]

8
.
Diagnostics
Chart
with
Trouble
Code
by
ABS
Warning
Light

8S6
CHECK
ANY

I
APPEARANCE

.THER
TROUBLE
CODES

CHECK
:
Are
other
trouble
codes
being
output?

,rES
:
Proceed
with
thediagnosis
corresponding
to
the

trouble
code
.

No
:
A
temporary
poor
contact
.

64