1997 SUBARU LEGACY brake sensor

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].>
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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

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
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3. Electrical Components Location

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
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4. Schematic

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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5. Control Module I/O Signal

Contents Connector No. Terminal No.Input/Output signals
Measured value and measuring conditions
TCS
control
unit ECM
commun-
icationTCS,ECM communication
(torque command)P6 14—GNDLess than 0.7 V when the vehicle stands
still.
TCS,ECM communication
(torque command)P6 5—GNDLess than 5 V when the vehicle stands
still.
TCS,ECM communication
(TCS operates)P6 12—GND4—5.4 V when TCS controls no
operations. Less than 0.7 V when it
controls operations.
ECM,TCS communication
(engine control)P6 4—GNDH/L toggle signal with the accelerator
pedal off (Cycle 20 mS, H: 10—14 V, L:
less than 0.7 V). Less than 2.0 V with the
accelerator pedal depressed. Also when
TCS OFF indicator light comes on by TCS
OFF switch.
ABS operation signal P6 13—GND10—14 V when the ABS control does not
operate still and less than 0.7 V when
ABS operates.
Fluid level sensor P7 20—GNDLess than2VwhenIGNisONand10—
14 V when idling.
Select
monitorData is received. P7 9—GND 4—4.5 V when no data is received.
Data is sent. P7 19—GND 4—4.5 V when no data is sent.
Diagnosis connector P7 8—GND 10—14 V when IGN is ON.
Power
supplyIgnition P5 1—GND 10—14 V when IGN is ON.
Battery P5 4—GND 10—14 V
Grounding
linePower P5 5—body 1Ωor less
Digital P7 15—body 1Ωor less
Power P4 6—body 1Ωor less
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5. Control Module I/O Signal

3. LIST OF ABS/TCS ON-BOARD DIAGNOSTICS
FUNCTIONS
Trouble codeDiagnostic items
Detection timingIndicator
light ON
Parts concerned
At initial checking
Under no control
Under ABS control
Under TCS control
In diagnostic mode
ABS warning light
TCS warning light
TCS OFF indicator light
21 FR
23 FL
25 RR
27 RLDetection of fault in ABS sensor hardware

 —ABS sensor (ABS/TCS C/M)
22 FR
24 FL
26 RR
28 RLDetection of fault in ABS sensor software
 —ABS sensor (ABS/TCS C/M)
 —ABS sensor harness circuit (ABS/TCS C/M)
Detection of fault in ABS sensor software
—ABS sensor and solenoid valve (ABS/TCS C/M)
—ABS sensor (ABS/TCS C/M)
Detection of fault in sensor software
 —ABS sensor (ABS/TCS C/M)
31 FRI
32 FRO
33 FLI
34 FLO
35 RRI
36 RRO
37 RLI
38 RLO
61 TCS1
62 TCS2Abnormal valve

*
—Solenoid valve (ABS/TCS C/M)
41 Abnormal ABS/TCS C/M
 —ABS/TCS C/M
42 Abnormal line voltage
—Power source operating environment (ABS/TCS C/M)
—Power source voltage drop
 —
—
*: Except when trouble code is being displayed.
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5. Control Module I/O Signal

Trouble codeDiagnostic items
Detection timingIndicator
light ON
Parts concerned
At initial checking
Under no control
Under ABS control
Under TCS control
In diagnostic mode
ABS warning light
TCS warning light
TCS OFF indicator light
54 Abnormal pedal stroke sensor and stop light switch
 —Pedal stroke sensor (ABS/TCS C/M)
Abnormal pedal stroke sensor and stop light switch
—Pedal stroke sensor (ABS/TCS C/M)
Abnormal pedal stroke sensor and stop light switch
—Stop light switch, pedal stroke sensor (ABS/TCS C/M)
Abnormal pedal stroke sensor and stop light switch
—Pump, pedal stroke sensor (ABS/TCS C/M)
Abnormal stroke sensor and stop light switch
——Stop light switch circuit (ABS/TCS C/M)
57 Abnormal fluid level sensor
—Fluid level sensor circuit
—Abnormal fluid level sensor

 —Fluid level sensor circuit, reservoir
58 Abnormal pressure switch
——Pressure switch (ABS/TCS C/M)
——Pressure switch, stop light switch (ABS/TCS C/M)
——Pressure switch (ABS/TCS C/M)
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5. Control Module I/O Signal