SUBARU LEGACY 1996 Service Repair Manual

1. Supplemental Restraint System
“Airbag”
Airbag system wiring harness is routed near the ABS con-
trol 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 control module, ABS
sensor and hydraulic control unit.
2. Pre-inspection
Before performing diagnostics, check the following items
which might affect ABS 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. <Ref. to 4-4 [K100].>
4. BRAKE PAD AND ROTOR
Check brake pad and rotor. <Ref. to 4-4 [K100].>
5. TIRE SPECIFICATIONS, TIRE WEAR AND AIR
PRESSURE
Check tire specifications, tire wear and air pressure. <Ref.
to 4-2 [S1A2].>
2
4-4cBRAKES [ABS 5.3 TYPE]
1. Supplemental Restraint System“Airbag”- 2. Pre-inspection

1. Supplemental Restraint System
“Airbag”
Airbag system wiring harness is routed near the ABS con-
trol 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 control module, ABS
sensor and hydraulic control unit.
2. Pre-inspection
Before performing diagnostics, check the following items
which might affect ABS 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. <Ref. to 4-4 [K100].>
4. BRAKE PAD AND ROTOR
Check brake pad and rotor. <Ref. to 4-4 [K100].>
5. TIRE SPECIFICATIONS, TIRE WEAR AND AIR
PRESSURE
Check tire specifications, tire wear and air pressure. <Ref.
to 4-2 [S1A2].>
2
4-4cBRAKES [ABS 5.3 TYPE]
1. Supplemental Restraint System“Airbag”- 2. Pre-inspection

B: ELECTRICAL INSPECTION
1. WARNING LIGHT ILLUMINATION PATTERN
B4M0781A
1) When the ABS warning light does not illuminate in
accordance with this illumination pattern, there must be an
electrical malfunction.
2) When the ABS warning light remains constantly OFF,
refer to“7. Diagnostics Chart for ABS Warning Light Circuit
and Diagnosis Circuit Failure”in this section, for repair.
<Ref. to 4-4c [T7A0].>
3
4-4cBRAKES [ABS 5.3 TYPE]
2. Pre-inspection

3. Electrical Components Location
B4M0782A
1Hydraulic control unit (H/U)

2Proportioning valve

3ABS control module (ABSCM)

4Diagnosis connector

5ABS warning light

6Data link connector (for Subaru select monitor)

7Transmission control module (only AT vehicle)
8Tone wheel

9ABS sensor

10Wheel cylinder

11G sensor (only AWD vehicle)

12Brake switch

13Master cylinder

14Relay box
4
4-4cBRAKES [ABS 5.3 TYPE]
3. Electrical Components Location

B4M0783AB4M0784A
B4M0230B
B4M0786A
B4M0646BB4M0231B
B4M0645B
5
4-4cBRAKES [ABS 5.3 TYPE]
3. Electrical Components Location

4. Schematic
B4M0787A
1Hydraulic control unit (H/U)

2Front left inlet solenoid valve

3Front left outlet solenoid valve

4Front right inlet solenoid valve

5Front right outlet solenoid valve

6Rear left inlet solenoid valve

7Rear left outlet solenoid valve

8Rear right inlet solenoid valve

9Rear right outlet solenoid valve

10Motor

11Transmission control module (only AT model)

12ABS warning light

13Motor relay
14Valve relay

15Relay box

16Data link connector

17Diagnosis connector

18Stop light switch

19Stop light

20G sensor (only AWD model)

21Front left ABS sensor

22Front right ABS sensor

23Rear left ABS sensor

24Rear right ABS sensor

25ABS control module (ABSCM)
6
4-4cBRAKES [ABS 5.3 TYPE]
4. Schematic

5. Control Module I/O Signal
1. I/O SIGNAL VOLTAGE
B4M1024A
NOTE:

The connector covers of LHD and RHD vehicles are in
the reverse directions.

The terminal numbers in the ABS control module con-
nector are as shown in the figure.
7
4-4cBRAKES [ABS 5.3 TYPE]
5. Control Module I/O Signal

Contents Terminal No.Input/Output signal
Measured value and measuring conditions
ABS sensor
(Wheel
speed
sensor)Front left wheel 49—19
0.12—1V
(When it is 20 Hz.) Front right wheel 14—15
Rear left wheel 16—17
Rear right wheel 18—46
Hydraulic
control unitSolenoid
valveFront left outlet 51—1
10—13 V when the valve is OFF and
less than 1.5 V when the valve is ON. Front right outlet 3—1
Rear left outlet 4—1
Rear right outlet 50—1
Front left inlet 24—1
Front right inlet 30—1
Rear left inlet 31—1
Rear right inlet 23—1
Relay boxValve relay power supply 27—110—13 V when ignition switch is ON.
Valve relay coil 47—1 Less than 1.5 V when ignition switch is ON.
Motor relay coil 22—1More than 10 V when the ABS control does not operate still
and less than 1.5 V when ABS operates.
Motor monitoring 10—1Less than 1.5 V when the ABS control does not operate still
and more than 10 V when ABS operates.
G sensor
(AWD
model only)power supply 8—45 4.75—5.25 V
ground 45—
output 7—45 2.3±0.2 V when vehicle is in horizontal position.
Stop light switch 36—1Less than 1.5 V when the stop light is OFF and more than
4.5 V when the stop light is ON.
ABS warning light 54—1Less than 1.5 V during 1.5 seconds when ignition switch is
ON, and 10—14 V after 1.5 seconds.
AT ABS signal
(AT model only)12—1Less than 1.5 V when the ABS control does not operate still
and more than 5.5 V when ABS operates.
ABS operation signal monitor 39—1Less than 1.5 V when the ABS control does not operate still
and more than 5.5 V when ABS operates.
Select
monitorData is received. 11—1 Less than 1.5 V when no data is received.
Data is sent. 38—1 4.75—5.25 V when no data is sent.
Diagnosis
connectorTerminal No. 3 5—110—14 V when ignition switch is ON.
Terminal No. 6 13—110—14 V when ignition switch is ON.
Power supply 28—110—14 V when ignition switch is ON.
Grounding line 1—
Grounding line 55—
8
4-4cBRAKES [ABS 5.3 TYPE]
5. Control Module I/O Signal

2. I/O SIGNAL DIAGRAM
B4M0788A
9
4-4cBRAKES [ABS 5.3 TYPE]
5. Control Module I/O Signal

6. Diagnostics Chart for On-board
Diagnosis System
A: BASIC DIAGNOSTICS PROCEDURE
TROUBLE OCCURS.
Is Select Monitor available?
No
Ye s
10. Diagnostic Chart with Select
Monitor <Ref. to 4-4c [T10A0].>
Ask the customer when and how the
trouble occurred using interview
check list. <Ref. to 4-4c [T6B0].>
PRE-INSPECTION
<Ref. to 4-4c [T200].>
CALLING UP A TROUBLE CODE.
<Ref. to 4-4c [T6D1].>No trouble code is readable.

Inspection using Diagnostic Chart for
Warning Light Failure.
<Ref. to 4-4c [T700].>
Record all trouble codes.
Trouble codes
are issued.
Only the start code is issued.
Inspection using General Diagnostics
Chart
<Ref. to 4-4c [T1100].>
Perform diagnostics in accordance with trouble code.
<Ref. to 4-4c [T8A0].>
Trouble code
designated.

Repair.
Clear memory.
<Ref. to 4-4c [T6D2].>
INSPECTION MODE
<Ref. to 4-4c [T6C0].>
CALLING UP A TROUBLE CODE.
<Ref. to 4-4c [T6D1].>
Only the start code is issued.
CONFIRMATION TEST
END
NOTE:

To check harness for broken wires or short circuits,
shake it while holding it or the connector.

When ABS warning light illuminates, read and record
trouble code indicated by ABS warning light.












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4-4cBRAKES [ABS 5.3 TYPE]
6. Diagnostics Chart for On-board Diagnosis System