Control unit SUBARU LEGACY 1995 Service Manual PDF

4. Schematic
B4M0647A
1Hydraulic control unit

2Motor

3Motor relay

4Front left solenoid valve

5Front right solenoid valve

6Rear solenoid valve

7Valve relay

8AT control module

9A.B.S. control module

10Warning light
11Stop light

12Stop light switch

13G sensor (AWD MT model)

14Ignition switch

15Battery

16Front left sensor

17Front right sensor

18Rear left sensor

19Rear right sensor

20Diagnosis connector
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4. Schematic

5. Control Module I/O Signal
1. I/O SIGNAL VOLTAGE
G4M0685
ContentsTerminal
No.Ignition
switch ON,
engine
OFFInput/output signals
Measured value Measuring conditions
A.B.S.
sensorFront left wheel 22
0 V 0.12—1V
No. 22—No. 4
(When it is 10 Hz.)
GND 4
Front right wheel 23
0 V 0.12—1V
No. 23—No. 21
(When it is 10 Hz.)
GND 21
Rear left wheel 8
0 V 0.12—1V
No. 8—No. 9
(When it is 10 Hz.)
GND 9
Rear right wheel 24
0 V 0.12—1V
No. 24—No. 26
(When it is 10 Hz.)
GND 26
G sensor (AWD MT model) 13 10—12 V 0 V When slanting about 14°—21.3°(θ)
Diagnosis connector30
—— —
31
Stop light switch 25 0 V 10—12 V When brake pedal is depressed.
Motor monitoring 14 0 V 10—12 V When motor operates.
Valve power supply monitoring 32 10—12 V 10—12 V Ignition switch ON*1
Hydraulic
control
unitSolenoidFront left
wheel210—12 V 0 V
When solenoid is energized to
produce output. Front right
wheel35 10—12 V 0 V
Rear wheel 18 10—12 V 0 V
Valve relay coil 27 0 V 0 V Ignition switch ON*2
Motor relay coil 28 10—12 V 0 VWhen motor operates to produce
output.
Warning light 29 10—12 V 10—12 V Ignition switch ON*3
Power
supplyIgnition 1 10—12 V 10—12 V Ignition switch ON
Relay coil (valve,
motor, etc.)17 10—12 V 10—12 V Ignition switch ON
Grounding line10 0V 0V—
20 0V 0V—
34 0V 0V—
*1: When ignition switch is OFF or the A.B.S. system is inactive: 0 V
*2: When ignition switch is OFF or the A.B.S. system is inactive: 10—12 V
*3: When ignition switch is OFF or the A.B.S. system is inactive, or during 1.5 seconds from ignition switch ON: 0 V
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5. Control Module I/O Signal

B: INSPECTION MODE
The on-board diagnosis system is designed to detect prob-
lems after the vehicle has been driven at 10 km/h (6 MPH)
or more for at least 20 seconds. If a problem is found, the
A.B.S. warning light will illuminate to inform the driver of the
occurrence of a problem. When the warning light is on, the
A.B.S. system will be inactive and the normal braking func-
tion will work. It is possible for a maximum of three trouble
codes to be stored in memory until cleared.
B4M0082A
C: TROUBLE CODES
When on-board diagnosis of the A.B.S. control module
detects a problem, the information (up to a maximum of
three) will be stored in the EEP ROM as a trouble code.
When there are more than three, the most recent three will
be stored. (Stored codes will stay in memory until they are
cleared.)
1. CALLING UP A TROUBLE CODE
1) Take out diagnosis connector from side of driver’s seat
heater unit.
2) Turn ignition switch OFF.
3) Connect diagnosis connector terminal 6 (terminal L) to
diagnosis terminal.
4) Turn ignition switch ON.
5) A.B.S. warning light is set in the diagnostic mode and
blinks to identify trouble code.
6) After the start code (11) is shown, the trouble codes will
be shown in order of the last information first.
These repeat for a maximum of 5 minutes.
NOTE:
When there are no trouble codes in memory, only the start
code (11) is shown.
B4M0232A
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6. Diagnostics Chart for On-board Diagnosis System

7. Diagnostics Chart with Trouble Code
Trouble code Contents of diagnosis Ref. to 4-4a
NONE: A
[Warning light OFF]Trouble in warning light drive circuit
(Warning light is not on for 1.5 seconds after ignition switch is on.)[T7A0]
NONE: B
[Warning light ON] or
[Abnormal trouble code output]Trouble in warning light drive circuit [T7B0]
11Start code:

Trouble code is shown after start code.

Only start code is shown in normal condition.—
21
Faulty A.B.S. sensor
(Open circuit or input voltage
excessive)Front right wheel sensor [T7C0]
23 Front left wheel sensor [T7C0]
25 Rear right wheel sensor [T7C0]
27 Rear left wheel sensor [T7C0]
22
Faulty A.B.S. sensor
(When there is no open circuit or
speed signal input.)Front right wheel sensor [T7D0]
24 Front left wheel sensor [T7D0]
26 Rear right wheel sensor [T7D0]
28 Rear left wheel sensor [T7D0]
29 Faulty tone wheel, etc. [T7E0]
31
Faulty solenoid valve circuit(s) in
hydraulic control unitFront right wheel control [T7F0]
33 Front left wheel control [T7F0]
39 Rear wheels control [T7F0]
41 Faulty A.B.S. control module [T7G0]
42 Source voltage is low. [T7H0]
51 Faulty valve relay [T7I0]
52 Faulty hydraulic motor and/or motor relay [T7J0]
54 Faulty stop light circuit [T7K0]
56 Use of improper A.B.S. control module specification, or faulty G sensor [T7L0]
NOTE:
After diagnostics is completed, make sure to clear memory.
Make sure only start code (11) is shown after memory is
cleared.
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7. Diagnostics Chart with Trouble Code

A: TROUBLE CODE (NONE: A)
—TROUBLE IN WARNING LIGHT DRIVE
CIRCUIT—
DIAGNOSIS:

Faulty A.B.S. warning light

Faulty harness connector

Faulty A.B.S. control module

Faulty valve relay
TROUBLE SYMPTOM:

Warning light does not illuminate.

Impossible to read trouble code.
NOTE:
When ignition key is on, warning light should turn off after
1.5 seconds if system is normal.
1. Check A.B.S. warning light power supply.
OK
Not OK
Repair A.B.S. warning light power line.
2. Check input voltage of A.B.S. control module
and hydraulic control unit from A.B.S. warn-
ing light.
OK
Not OK
Repair harness/connector.
3. Check ground line of A.B.S. control module
and hydraulic control unit.
OK
Not OK
Repair ground line.
4. Check valve relay.
OK
Not OK
Replace valve relay.
Replace A.B.S. control module and hydraulic control
unit.




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7. Diagnostics Chart with Trouble Code

B4M0236B
2. CHECK INPUT VOLTAGE OF A.B.S. CONTROL
MODULE AND HYDRAULIC CONTROL UNIT FROM
A.B.S. WARNING LIGHT.
1) Turn ignition switch OFF and remove combination
meter.
2) Disconnect connector from A.B.S. control module and
hydraulic control unit.
3) Turn ignition switch ON.
4) Measure voltage between A.B.S. control module and
body, and between hydraulic control unit and body.
Connector & terminal / Specified voltage:
(P3) No. 29—body / 10—12 V
(F9) No. 10—body / 10—12 V
B4M0237B
3. CHECK GROUND LINE OF A.B.S. CONTROL
MODULE AND HYDRAULIC CONTROL UNIT.
Measure resistance between A.B.S. control module and
body, and between hydraulic control unit and body.
Connector & terminal / Specified resistance:
(P3) No. 10—body / 0Ω
(P3) No. 20—body / 0Ω
(P3) No. 34—body / 0Ω
(F9) No. 8—body / 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

B: TROUBLE CODE (NONE: B)
—TROUBLE IN WARNING LIGHT DRIVE
CIRCUIT—
DIAGNOSIS:

Faulty harness

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

Warning light remains on.

Impossible to read trouble code.
Check trouble code while the hydraulic control unit
valve relay is removed.
Not OK
OK
Perform diagnostics in accordance with trouble
code.
Make sure warning light is off when the valve relay
and A.B.S. control module is removed.
OK
Not OK
Harness is shorted to body.
Repair harness/connector.
1. Check input voltage to A.B.S. control module
from A.B.S. warning light.
OK
Not OK
Repair harness/connector.
2. Check power supply to A.B.S. control module.
OK
Not OK
Repair harness/connector.
3. Check A.B.S. control module ground line.
OK
Not OK
Repair harness/connector.
Replace A.B.S. control module.





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7. Diagnostics Chart with Trouble Code

F: TROUBLE CODE 31, 33 AND 39
—FAULTY SOLENOID VALVE CIRCUIT(S) IN
HYDRAULIC CONTROL UNIT—
DIAGNOSIS:

Faulty harness/connector

Faulty solenoid valve in hydraulic control unit

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

A.B.S. does not operate.
1. Check resistance of solenoid valve
to A.B.S. control module side.
OK
Not OK
4. Check resistance of sole-
noid valve.
OK
Not OK
Replace hydraulic control unit.
Repair harness/connector.
2. Check voltage of solenoid valve to
A.B.S. control module side.
OK
Not OK
5. Check GND short of
hydraulic control unit.
OK
Not OK
Replace hydraulic control unit.
Repair harness/connector.
3. Check voltage of solenoid valve to
A.B.S. control module side.
OK
Not OK
6. Check battery short of
hydraulic control unit.
OK
Not OK
Replace hydraulic control unit.
Replace A.B.S. control module.Repair harness/connector.
B4M0712





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7. Diagnostics Chart with Trouble Code

B4M0256B
1. CHECK RESISTANCE OF SOLENOID VALVE TO
A.B.S. CONTROL MODULE SIDE.
1) Turn ignition switch OFF.
2) Disconnect connector from A.B.S. control module.
3) Measure resistance between A.B.S. control module
connector terminals.
TROUBLE CODE / Connector & terminal:
31 / (P3) No. 35—No. 32
33 / (P3) No. 2—No. 32
39 / (P3) No. 18—No. 32
Specified resistance: approx. 1Ω
B4M0257B
2. CHECK VOLTAGE OF SOLENOID VALVE TO A.B.S.
CONTROL MODULE SIDE.
1) Turn ignition switch OFF.
2) Disconnect valve relay from hydraulic control unit.
3) Turn ignition switch ON.
4) Measure voltage between A.B.S. control module con-
nector terminals.
TROUBLE CODE / Connector & terminal:
31 / (P3) No. 35—No. 20
33 / (P3) No. 2—No. 20
39 / (P3) No. 18—No. 20
Specified voltage: 10—12 V
B4M0257B
3. CHECK VOLTAGE OF SOLENOID VALVE TO A.B.S.
CONTROL MODULE SIDE.
1) Turn ignition switch OFF.
2) Disconnect combination meter fuse No. 15.
3) Turn ignition switch ON.
4) Measure voltage between A.B.S. control module con-
nector terminals.
TROUBLE CODE / Connector & terminal:
31 / (P3) No. 35—No. 20
33 / (P3) No. 2—No. 20
39 / (P3) No. 18—No. 20
Specified voltage: 0 V
31
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7. Diagnostics Chart with Trouble Code

B4M0259B
4. CHECK RESISTANCE OF SOLENOID VALVE.
1) Turn ignition switch OFF.
2) Disconnect connector from hydraulic control unit.
3) Measure resistance between hydraulic control unit ter-
minals.
TROUBLE CODE / Connector & terminal:
31 / to (F9) No. 4—No. 11
33 / to (F9) No. 3—No. 11
39 / to (F9) No. 1—No. 11
Specified resistance: approx. 1Ω
B4M0702A
5. CHECK GND SHORT OF HYDRAULIC CONTROL
UNIT.
1) Turn ignition switch OFF.
2) Disconnect connector from hydraulic control unit.
3) Measure resistance between hydraulic control unit ter-
minals.
Connector & terminal / Specified resistance:
(F9) No. 11—body/1MΩ
(F9) No. 11—No.8/1MΩ
B4M0259B
B4M0703A
6. CHECK BATTERY SHORT OF HYDRAULIC
CONTROL UNIT.
1) Turn ignition switch OFF.
2) Disconnect connector from hydraulic control unit.
3) Measure resistance between hydraulic control unit ter-
minals.
TROUBLE CODE / Connector & terminal:
31 / to (F9) No. 4—No. 11
33 / to (F9) No. 3—No. 11
39 / to (F9) No. 1—No. 11
Specified resistance: approx. 1Ω
4) Turn ignition ON.
5) Measure voltage between hydraulic control unit termi-
nals.
Connector & terminal / Specified voltage:
(F9) No. 11—body/0V
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7. Diagnostics Chart with Trouble Code