Control unit SUBARU LEGACY 1995 Service Manual PDF

H: TROUBLE CODE 42
—SOURCE VOLTAGE IS LOW.—
DIAGNOSIS:

Faulty battery

Faulty A.B.S. control module

Faulty harness

Faulty valve relay
TROUBLE SYMPTOM:

A.B.S. does not operate.
Check battery.

OK
Not OK
Replace battery.
1. Check input voltage of A.B.S. control module.
Not OK
OK
Replace A.B.S. control module.
2. Check input voltage of hydraulic control unit.
OK
Not OK
Repair harness/connector.
3. Check harness connector between A.B.S. con-
trol module and hydraulic control unit.
OK
Not OK
Repair harness/connector.
4. Check valve relay.
OK
Not OK
Replace valve relay.
Replace hydraulic control unit.





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7. Diagnostics Chart with Trouble Code

B4M0262B
2. CHECK INPUT VOLTAGE OF HYDRAULIC
CONTROL UNIT.
1) Turn ignition switch OFF.
2) Disconnect connector from hydraulic control unit.
3) Turn ignition switch ON.
4) Measure input voltage between hydraulic control unit
connector and body.
Connector & terminal / Specified voltage:
(F8) No. 1—Body / 10—12 V
B4M0263B
3. CHECK HARNESS CONNECTOR BETWEEN A.B.S.
CONTROL MODULE AND HYDRAULIC CONTROL
UNIT.
1) Turn ignition switch OFF.
2) Disconnect connector from A.B.S. control module and
hydraulic control unit.
3) Measure resistance between A.B.S. control module and
hydraulic control unit.
Connector & terminal / Specified resistance:
(P3) No. 32—(F9) No. 11 / 0Ω
G4M0690
4. CHECK VALVE RELAY.
1) Remove valve relay.
2) Attach circuit tester probes to terminals, as shown in
figure.
3) Measure resistance between respective terminals.
Terminal / Specified resistance:
No. 87—No. 30 / 0Ω(when 12 volts applied.)
No. 87—No.30/1MΩ(when no volts applied.)
No. 87a—No.30/1MΩ(when 12 volts applied.)
No. 87a—No. 30 / 0Ω(when no volts applied.)
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7. Diagnostics Chart with Trouble Code

I: TROUBLE CODE 51
—FAULTY VALVE RELAY—
DIAGNOSIS:

Faulty valve relay

Faulty harness

Faulty A.B.S. control module
TROUBLE SYMPTOM:

A.B.S. does not operate.
1. Check power supply circuit of A.B.S. control
module.
OK
Not OK
Repair harness/connector.
2. Check output voltage to A.B.S. control
module.
OK
Not OK
Replace A.B.S. control module.
3. Check input voltage of A.B.S. control module.
Not OK
OK
Replace A.B.S. control module.
4. Check harness connector between A.B.S.
control module and hydraulic control unit.
OK
Not OK
Repair harness/connector.
5. Check power supply circuit of hydraulic
control unit.Not OK
Repair harness/connector.
6. Check valve relay.Replace valve relay.
Replace hydraulic control unit.






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7. Diagnostics Chart with Trouble Code

B4M0267B
2. CHECK OUTPUT VOLTAGE TO A.B.S. CONTROL
MODULE.
1) Turn ignition switch OFF.
2) Disconnect connector from A.B.S. control module.
3) Disconnect connector cover from connector. 4-4a [T7C2].>
4) Connect connector to A.B.S. control module.
5) Turn ignition switch ON.
6) Measure voltage between A.B.S. control module con-
nector terminals.
Connector & terminal / Specified voltage:
(P3) No. 17—No. 20 / 10—12 V
B4M0268B
3. CHECK INPUT VOLTAGE OF A.B.S. CONTROL
MODULE.
1) Turn ignition switch ON.
2) Measure voltage between A.B.S. control module con-
nector terminals.
Connector & terminal / Specified voltage:
(P3) No. 32—No. 20 / 10—12 V
B4M0269B
4. CHECK HARNESS CONNECTOR BETWEEN A.B.S.
CONTROL MODULE AND HYDRAULIC CONTROL
UNIT.
1) Turn ignition switch OFF.
2) Disconnect connector from A.B.S. control module and
hydraulic control unit.
3) Measure resistance between A.B.S. control module and
hydraulic control unit.
Connector & terminal / Specified resistance:
(P3) No. 17—(F9) No.6/0Ω
(P3) No. 32—(F9) No. 11 / 0Ω
(P3) No. 27—(F9) No. 12 / 0Ω
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7. Diagnostics Chart with Trouble Code

B4M0262B
5. CHECK POWER SUPPLY CIRCUIT OF HYDRAULIC
CONTROL UNIT.
1) Turn ignition switch OFF.
2) Disconnect connector from hydraulic control unit.
3) Turn ignition switch ON.
4) Measure voltage between hydraulic control unit and
body.
Connector & terminal / Specified voltage:
(F8) No. 1—Body / 10—12 V
G4M0690
6. CHECK VALVE RELAY.
1) Remove valve relay.
2) Attach circuit tester probes to terminals, as shown in
figure.
3) Measure resistance between respective terminals.
Terminal / Specified resistance:
No. 87—No. 30 / 0Ω(when 12 volts applied.)
No. 87—No.30/1MΩ(when no volts applied.)
No. 87a—No.30/1MΩ(when 12 volts applied.)
No. 87a—No. 30 / 0Ω(when no volts applied.)
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7. Diagnostics Chart with Trouble Code

J: TROUBLE CODE 52
—FAULTY HYDRAULIC MOTOR AND/OR
MOTOR RELAY—
DIAGNOSIS:

Faulty motor relay

Faulty hydraulic control unit

Faulty harness

Faulty A.B.S. control module
TROUBLE SYMPTOM:

A.B.S. does not operate.
1. Check power supply circuit of A.B.S. control
module.
OK
Not OK
Repair harness/connector.
2. Check output voltage of A.B.S. control
module.
OK
Not OK
Replace A.B.S. control module.
3. Check harness connector between A.B.S.
control module and hydraulic control unit.
OK
Not OK
Repair harness/connector.
4. Check power supply circuit of hydraulic
control unit.
OK
Not OK
Repair harness/connector.
5. Check motor relay.
OK
Not OK
Replace motor relay.
Check hydraulic motor ground harness.
OK
Not OK
Repair ground harness.
Replace hydraulic control unit.






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7. Diagnostics Chart with Trouble Code

B4M0267B
2. CHECK OUTPUT VOLTAGE OF A.B.S. CONTROL
MODULE.
1) Turn ignition switch OFF.
2) Disconnect connector from A.B.S. control module.
3) Disconnect connector cover from connector. 4-4a [T7C2].>
4) Connect connector to A.B.S. control module.
5) Turn ignition switch ON.
6) Measure voltage between A.B.S. control module con-
nector terminals.
Connector & terminal / Specified voltage:
(P3) No. 17—No. 20 / 10—12 V
B4M0275B
3. CHECK HARNESS CONNECTOR BETWEEN A.B.S.
CONTROL MODULE AND HYDRAULIC CONTROL
UNIT.
1) Turn ignition switch OFF.
2) Disconnect connector from A.B.S. control module.
3) Disconnect connector from hydraulic control unit.
4) Measure resistance between A.B.S. control module
connector and hydraulic control unit connector.
Connector & terminal / Specified resistance:
(P3) No. 17—(F9) No.6/0Ω
(P3) No. 28—(F9) No.5/0Ω
(P3) No. 14—(F9) No.7/0Ω
B4M0276B
4. CHECK POWER SUPPLY CIRCUIT OF HYDRAULIC
CONTROL UNIT.
1) Turn ignition switch OFF.
2) Disconnect connector from hydraulic control unit.
3) Measure voltage between hydraulic control unit connec-
tor and body.
Connector & terminal / Specified voltage:
(F8) No. 2—Body / 10—12 V
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7. Diagnostics Chart with Trouble Code

B: EXCESSIVE STOPPING DISTANCE
Stopping distance is
too great.Snowy or sandy (low“µ”) roadsStopping distance may sometimes be longer
than for models not equipped with A.B.S.
Check if stopping
distance continues
to be excessive
when A.B.S. is inac-
tivated by discon-
necting hydraulic
control unit connec-
tor.
Ye sCheck wheels and
associated parts for
looseness.
Check tires for
improper specifica-
tions.
Check G sensor for
improper operation.
Bleed air from brake
line.
Check brake system
for abnormalities.
NoHydraulic control
unit operation
check.
[W15B0].>NoCheck hydraulic
control unit.
Ye sGo to A-1.
C: IMPROPER PEDAL OPERATION
Pedal does not
operate prop-
erly.
Long pedal
stroke
Check if brakes
operate prop-
erly.
Ye sOn A.B.S. equipped model, pedal stroke may be
slightly longer than for models which are not
equipped with A.B.S.
NoBleed air from
brake line.
Short pedal
stroke
Check if brakes
operate prop-
erly.
Ye sNormal
NoCheck if brakes
operate prop-
erly when
A.B.S. is inacti-
vated by dis-
connecting
hydraulic con-
trol unit connec-
tor.Ye sGo to A-1.
NoCheck brake
system.

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8. General Diagnostics Chart

1. Supplemental Restraint System
“Airbag”
Airbag system wiring harness is routed near the ABS/TCS
control module, ABS sensor and hydraulic control unit.
CAUTION:

All Airbag system wiring harness and connectors
are colored yellow. Do not use electrical test equip-
ment on these circuit.

Be careful not to damage Airbag system wiring har-
ness when servicing the ABS/TCS control module,
ABS sensor and hydraulic control unit.
2. Pre-inspection
Before performing diagnostics, check the following items
which might affect ABS/TCS problems:
A: MECHANICAL INSPECTION
1. POWER SUPPLY
1) Measure battery voltage and specific gravity of electro-
lyte.
Standard voltage: 12 V, or more
Specific gravity: Above 1.260
2) Check the condition of the main and other fuses, and
harnesses and connectors. Also check for proper ground-
ing.
2. BRAKE FLUID
1) Check brake fluid level.
2) Check brake fluid leakage.
3. BRAKE DRAG
Check brake drag.
4. BRAKE PAD AND ROTOR
Check brake pad and rotor.
5. TIRE SPECIFICATIONS, TIRE WEAR AND AIR
PRESSURE
Check tire specifications, tire wear and air pressure. to 4-2 [S1A0].>
2
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1. Supplemental Restraint System“Airbag”- 2. Pre-inspection

1. Supplemental Restraint System
“Airbag”
Airbag system wiring harness is routed near the ABS/TCS
control module, ABS sensor and hydraulic control unit.
CAUTION:

All Airbag system wiring harness and connectors
are colored yellow. Do not use electrical test equip-
ment on these circuit.

Be careful not to damage Airbag system wiring har-
ness when servicing the ABS/TCS control module,
ABS sensor and hydraulic control unit.
2. Pre-inspection
Before performing diagnostics, check the following items
which might affect ABS/TCS problems:
A: MECHANICAL INSPECTION
1. POWER SUPPLY
1) Measure battery voltage and specific gravity of electro-
lyte.
Standard voltage: 12 V, or more
Specific gravity: Above 1.260
2) Check the condition of the main and other fuses, and
harnesses and connectors. Also check for proper ground-
ing.
2. BRAKE FLUID
1) Check brake fluid level.
2) Check brake fluid leakage.
3. BRAKE DRAG
Check brake drag.
4. BRAKE PAD AND ROTOR
Check brake pad and rotor.
5. TIRE SPECIFICATIONS, TIRE WEAR AND AIR
PRESSURE
Check tire specifications, tire wear and air pressure. to 4-2 [S1A0].>
2
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1. Supplemental Restraint System“Airbag”- 2. Pre-inspection