1997 SUBARU LEGACY AUX

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