Page 1681 of 2248
![SUBARU LEGACY 1995 Service Repair Manual BRAKES
[ABS/TCS]
4-4b
Page
T DIAGNOSTICS
................................................................................2
1. Supplemental Restraint System “Airbag” ............................... SUBARU LEGACY 1995 Service Repair Manual BRAKES
[ABS/TCS]
4-4b
Page
T DIAGNOSTICS
................................................................................2
1. Supplemental Restraint System “Airbag” ...............................](/manual-img/17/57432/w960_57432-1680.png)
BRAKES
[ABS/TCS]
4-4b
Page
T DIAGNOSTICS
................................................................................2
1. Supplemental Restraint System “Airbag” ................................................2
2. Pre-inspection ..........................................................................................2
3. Electrical Components Location ..............................................................4
4. Schematic ................................................................................................6
5. Control Module I/O Signal .......................................................................7
6. Diagnostics Chart for On-board Diagnosis System...............................13
7. Diagnostics Chart for Warning Light Circuit Failure ..............................18
8. Diagnostics Chart with Trouble Code ....................................................35
9. Select Monitor Function Mode ...............................................................88
10. Diagnostics Chart with Select Monitor...................................................96
11. General Diagnostics Table ...................................................................130
12. Phenomena Peculiar to the System ....................................................131
Page 1682 of 2248

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
4-4bBRAKES
1. Supplemental Restraint System“Airbag”- 2. Pre-inspection
Page 1683 of 2248

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
4-4bBRAKES
1. Supplemental Restraint System“Airbag”- 2. Pre-inspection
Page 1684 of 2248
B: ELECTRICAL INSPECTION
1. WARNING LAMP ILLUMINATION PATTERN
B4M0372A
2. DISPLAY SYSTEM TYPE AND LIGHTING
CONDITIONS
: Illuminated
Mode
ABS warning
TCS warning
TCS OFF
TCS operating
Lighting conditions
Bulb checkIlluminated with IGN. ON, extinguished with E/G RUN
Illuminated with IGN. ON, extinguished after a few seconds.
Illuminated with IGN. ON, extinguished after 1 second.
ABS failureIlluminated during ABS failure (ABS and TCS functions stop)
TCS failureIlluminated during TCS failure (Only TCS functions stop)
TCS OFF
Illuminated when TCS operation is prohibited by E/G (low temperature, high
temperature, etc.); illuminated during TCS OFF conditions resulting from operation
of TCS OFF SW.
TCS operationIlluminated during TCS operation
Pad temperature warning
Illuminated when pad temperature reaches 400°C (752°F) or more when TCS is
functioning, and extinguished when temperature drops below 350°C (662°F).
3
4-4bBRAKES
2. Pre-inspection
Page 1685 of 2248
3. Electrical Components Location
B4M0373A
1Hydraulic control unit
2Engine control module
3AT control module
4TCS warning light
5ABS warning light
6Diagnosis connector
7TCS operating indicator light
8TCS OFF indicator light
9TCS OFF switch
10Data link connector (for Subaru select monitor)
11Data link connector (for Subaru select monitor and OBD-II
general scan tool)
12Tone wheel
13ABS sensor
14Stroke sensor
15ABS/TCS control module
4
4-4bBRAKES
3. Electrical Components Location
Page 1686 of 2248
B4M0374AB4M0376AB4M0646A
B4M0377AB4M0379AB4M0378A
B4M0375AB4M0645A
5
4-4bBRAKES
3. Electrical Components Location
Page 1687 of 2248
4. Schematic
B4M0380A
1Hydraulic control unit
2Valve relay
3Motor relay
4Motor
5Motor sensor
6Front left inlet solenoid valve
7Front left outlet solenoid valve
8Rear right inlet solenoid valve
9Rear right outlet solenoid valve
10TCS solenoid valve 2
11Front right inlet solenoid valve
12Front right outlet solenoid valve
13Rear left inlet solenoid valve
14Rear left outlet solenoid valve
15TCS solenoid valve 1
16Pressure switch
17Data link connector
18ABS/TCS control module
19ABS warning light
20TCS operating indicator light
21TCS OFF indicator light
22TCS warning light
23Stroke sensor
24TCS OFF switch
25Diagnosis connector
26Engine control module
27Rear right ABS sensor
28Front right ABS sensor
29Front left ABS sensor
30Rear left ABS sensor
31Brake warning light
32Parking brake switch
33Brake fluid level sensor
34Generator
35Stop lamp switch
36Stop lamp
37AT control module
6
4-4bBRAKES
4. Schematic
Page 1688 of 2248

5. Control Module I/O Signal
1. I/O SIGNAL VOLTAGE
Contents Connector No. Terminal No.Input/Output signals
Measured value and measuring conditions
ABS
sensor
(Wheel
speed
sensor)Front left wheel P7 1—11 0.12—1 V (When it is 10 Hz.)
Front right wheel P6 8—16 0.12—1 V (When it is 10 Hz.)
Rear left wheel P6 7—15 0.12—1 V (When it is 10 Hz.)
Rear right wheel P7 2—12 0.12—1 V (When it is 10 Hz.)
Hydraulic
unitSolenoid
valveFront left outlet P4 1—GND
10—14 V when the valve is OFF.
Less than 1.5 V when the valve is ON. Front right outlet P5 3—GND
Rear left outlet P5 8—GND
Rear right outlet P4 3—GND
Front left inlet P4 2—GND
10—14 V when the valve is OFF.
Less than 1.0 V when the valve is ON. Front right inlet P5 2—GND
Rear left inlet P5 7—GND
Rear right inlet P4 4—GND
TCS 1 P4 5—GND
10—14 V when the valve is OFF.
Less than 1.0 V when the valve is ON.
TCS 2 P5 6—GND
Valve power supply P6 6—GND Ignition switch ON, 10—14 V
Valve relay power supply P6 1—GNDLess than 1.2 V when IGN is ON.
10—14 V when the system is down.
Motor relay power supply P6 9—GNDLess than 1.0 V when the motor is ON.
10—14 V when the motor is OFF.
Motor sensor signalsP7 3—GNDCyclic waveform of more than 180 Hz
when the motor across terminals is ON.
Less than 70 Hz when the motor is OFF. P7 13—GND
Pressure switch P7 6—GNDH/L toggle signal with the brake pedal off
(Cycle 14 mS, H: 10—14 V, L: less than
0.7 V). 10—14 V with the brake pedal
depressed.
Pedal
stroke
sensorOutput signals P7 5—GND 0.7—0.9 V with the brake pedal off.
Power supply P7 4—14 5±0.4 V
Stop light
switchSwitch P7 7—GNDLess than 2 V when the stop light is off.
10—12 V when the stop light is on.
Switch test signal P7 18—GNDH/L toggle signal with the brake pedal off
(Cycle 14 mS, H: 10—12 V, L: less than
0.7 V). Less than 2 V with the brake pedal
depressed.
TCS OFF switch P7 16—GNDLess than 2.0 V with the switch pressed
and 10—12 V with it released.
Indicator
lightTCS OFF P6 10—GND
Less than2Vwhenthelight is on and
10—12 V when it is off. TCS operation P6 11—GND
TCS warning P6 3—GND
ABS warning P6 2—GND
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4-4bBRAKES
5. Control Module I/O Signal