1997 SUBARU LEGACY ABS

A: REMOVAL
1) Disconnect ground cable from battery.
2) Remove air intake duct from engine 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.
B4M1224A
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 to let 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.
B4M1222
8) Remove ABSCM&H/U from engine compartment.
CAUTION:

ABSCM&H/U cannot be 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.

Apply a coat of rust-preventive wax (Nippeco LT or
GB) to bracket attaching bolt after tightening.

Do not pull harness disconnecting harness connec-
tor.
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22. ABS Control Module and Hydraulic Control Unit (ABSCM&H/U) (ABS 5.3i Type)

B: INSPECTION
1) Check connected and fixed condition of connector.
B4M1248A
2) Check specifications of the mark with ABSCM&H/U.
Mark Model
C3 AWD AT
C4 AWD MT
C: CHECKING THE HYDRAULIC UNIT ABS
OPERATION
1. CHECKING THE HYDRAULIC UNIT ABS
OPERATION BY PRESSURE GAUGE
1) Lift-up vehicle and remove wheels.
2) Disconnect the air bleeder screws from the FL and FR
caliper bodies.
B4M0633A
3) Connect two pressure gauges to the FL and FR caliper
bodies.
CAUTION:

Pressure gauges used exclusively for brake fluid
must be used.

Do not employ pressure gauge previously used for
transmission since the piston seal is expanded which
may lead to malfunction of the brake.
NOTE:
Wrap sealing tape around the pressure gauge.
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22. ABS Control Module and Hydraulic Control Unit (ABSCM&H/U) (ABS 5.3i Type)

4) Bleed air from the pressure gauges.
5) Perform ABS sequence control.

6) When the hydraulic unit begins to work, and first the FL
side performs decompression, holding, and compression,
and then the FR side performs decompression, holding,
and compression.
7) Read values indicated on the pressure gauge and
check if the fluctuation of the values between decompres-
sion and compression meets the standard values. Also
check if any irregular brake pedal tightness is felt.
Initial value When decompressed When compressed
Front wheel 3,432 kPa (35 kg/cm
2, 498 psi)490 kPa (5 kg/cm2, 71 psi)
or less3,432 kPa (35 kg/cm2, 498 psi)
or more
Rear wheel 3,432 kPa (35 kg/cm
2, 498 psi)490 kPa (5 kg/cm2, 71 psi)
or less3,432 kPa (35 kg/cm2, 498 psi)
or more
8) Remove pressure gauges from FL and FR caliper bod-
ies.
9) Remove air bleeder screws from the RL and RR caliper
bodies.
10) Connect the air bleeder screws to the FL and FR cali-
per bodies.
11) Connect two pressure gauges to the RL and RR cali-
per bodies.
12) Bleed air from the pressure gauges and the FL and FR
caliper bodies.
13) Perform ABS sequence control.

14) When the hydraulic unit begins to work, at first the RR
side performs decompression, holding, and compression,
and then the RL side performs decompression, holding,
and compression.
15) Read values indicated on the pressure gauges and
check if they meet the standard value.
16) After checking, remove the pressure gauges from cali-
per bodies.
17) Connect the air bleeder screws to RL and RR caliper
bodies.
18) Bleed air from brake line.
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22. ABS Control Module and Hydraulic Control Unit (ABSCM&H/U) (ABS 5.3i Type)

G4M0462
2. CHECKING THE HYDRAULIC UNIT ABS
OPERATION WITH BRAKE TESTER
1) In the case of AWD AT vehicles, install a spare fuse with
the FWD connector in the engine compartment to simulate
FWD vehicles.
2) Prepare for operating ABS sequence control. 4-4 [W22D1] or 4-4 [W22D2].>
G4M0464
3) Set the front wheels or rear wheels on the brake tester
and set the select lever’s position at“neutral”.
4) Operate the brake tester.
5) Perform ABS sequence control. step 1 or 4-4 [W22D2] step 1.>
6) Hydraulic unit begins to work; and check the following
working sequence.
(1) The FL wheel performs decompression, holding,
and compression in sequence, and subsequently the
FR wheel repeats the cycle.
(2) The RR wheel performs decompression, holding,
and compression in sequence, and subsequently the
RL wheel repeats the cycle.
7) Read values indicated on the brake tester and check if
the fluctuation of values, when decompressed and
compressed, meet the standard values.
Unit: N (kg, lb)
Initial value When decompressed When compressed
Front wheel 981 (100, 221) 490 (50, 110) or less 981 (100, 221) or more
Rear wheel 981 (100, 221) 490 (50, 110) or less 981 (100, 221) or more
8) After checking, also check if any irregular brake pedal
tightness is felt.
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22. ABS Control Module and Hydraulic Control Unit (ABSCM&H/U) (ABS 5.3i Type)

D: ABS SEQUENCE CONTROL
1) Under the ABS sequence control, after the hydraulic
unit solenoid valve is driven, the operation of the hydraulic
unit can be checked by means of the brake tester or pres-
sure gauge.
2) ABS sequence control can be started by diagnosis con-
nector or select monitor.
B4M0082D
1. OPERATIONAL GUIDELINES OF THE ABS
SEQUENCE CONTROL WITH DIAGNOSIS
CONNECTOR
1) Connect diagnosis terminals to terminals No. 3 and No.
6 of the diagnosis connector beside driver’s seat heater
unit.
2) Set the speed of all wheels at 4 km/h (2 MPH) or less.
3) Turn ignition switch OFF.
4) Within 0.5 seconds after the ABS warning light goes
out, depress the brake pedal and hold it immediately after
ignition switch is turned to ON.
CAUTION:
Do not depress the clutch pedal.
NOTE:

When the ignition switch is set to on, the brake pedal
must not be depressed.

Engine must not operate.
5) After completion of ABS sequence control, turn ignition
switch OFF.
2. OPERATIONAL GUIDELINES OF THE ABS
SEQUENCE CONTROL WITH SELECT MONITOR
NOTE:
In the event of any trouble, the sequence control may not
be operative. In such a case, activate the sequence
control, referring to“OPERATIONAL GUIDELINES OF
THE ABS SEQUENCE CONTROL WITH DIAGNOSIS
CONNECTOR”.
1) Connect select monitor to data link connector beside
driver’s seat heater unit.
2) Turn ignition switch ON.
3) Put select monitor to ABS mode.
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22. ABS Control Module and Hydraulic Control Unit (ABSCM&H/U) (ABS 5.3i Type)

B4M0635
4) PressFD1ENTkey.
B4M0997
5) The message shown in the figure is displayed.
B4M0998
6) The message shown in the figure is displayed as fol-
lows:
(1) When using the brake tester, depress brake pedal
with braking force of 981 N (100 kg, 221 lb).
(2) When using the pressure gauge, depress brake
pedal so as to make the pressure gauge indicate 3,432
kPa (35 kg/cm
2, 498 psi).
CAUTION:
Do not depress the clutch pedal.
B4M0999
7) When the message shown in the figure is displayed,
press ENT key.
8) Check points will be displayed on select monitor.
B4M1000
9) When ABS sequence control cannot be started (by sys-
tem malfunction, etc.), the message shown in the figure will
be displayed.
NOTE:
Read the trouble codes. Repair faulty parts.
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22. ABS Control Module and Hydraulic Control Unit (ABSCM&H/U) (ABS 5.3i Type)

B4M1030
10) After completion of ABS sequence control.
H4M1144
11) Press 0 key to start ABS sequence control again and
press 1 key to end.
3. CONDITIONS FOR COMPLETION OF ABS
SEQUENCE CONTROL
When the following conditions develop, the ABS sequence
control stops and ABS operation is returned to the normal
control mode.
1) When the speed of at least one wheel reaches 10 km/h
(6 MPH).
2) When terminal No. 3 or No. 6 are separated from diag-
nosis terminals. (When select monitor is not used.)
3) When the brake pedal is released during sequence con-
trol and the braking lamp switch is set to off.
4) When brake pedal is depressed after ignition key is
turned to ON, and before ABS warning light goes out.
(When select monitor is not used.)
5) When brake pedal is not depressed after ignition key is
turned to ON, and within 0.5 seconds after ABS warning
light goes out. (When select monitor is not used.)
6) After completion of the sequence control.
7) When malfunction is detected. (When select monitor is
used.)
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22. ABS Control Module and Hydraulic Control Unit (ABSCM&H/U) (ABS 5.3i Type)

4. CONDITIONS FOR ABS SEQUENCE CONTROL
B4M1001A
NOTE:

When select monitor is used, control operation starts at
point A. The patterns from IGN key ON to the point A show
that operation is started by diagnosis connector.

HIGH means high voltage.

LOW means low voltage.
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22. ABS Control Module and Hydraulic Control Unit (ABSCM&H/U) (ABS 5.3i Type)