brake sensor SUBARU LEGACY 1995 Service Service Manual

D: TROUBLE CODE 22, 24, 26 AND 28
—FAULTY A.B.S. SENSOR
(WHEN THERE IS NO OPEN CIRCUIT OR
SPEED SIGNAL INPUT.)—
DIAGNOSIS:

Faulty A.B.S. sensor/harness

Faulty tone wheel

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

A.B.S. does not operate.
NOTE:
The A.B.S. control module will sense that the A.B.S. sen-
sor circuit is“open”due to increased resistance but this
trouble code will appear when the speed signal is not
present or when it suddenly disappears while driving.
1. Check input signal of A.B.S. sensor to
A.B.S. control module side.
Not OK
OK
Check contact of A.B.S. control module connector
terminal.
Not OK OK
Repair A.B.S. control module connector.
Replace A.B.S. control module.
2. Check resistance of A.B.S. sensor.
Not OK
OK
Repair harness/connector.
3. Check A.B.S. sensor mechanical trouble.
Not OK
OK
Replace A.B.S. sensor.
Repair mechanical trouble.
NOTE:
When checking A.B.S. sensor, carefully bend or swing con-
nector and harness to check for improper contact or open
circuits.





22
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7. Diagnostics Chart with Trouble Code

B4M0711A
1. CHECK INPUT SIGNAL OF A.B.S. SENSOR TO
A.B.S. CONTROL MODULE SIDE.
1) Raise all four wheels of ground.
2) Turn ignition switch OFF.
3) Disconnect connector from A.B.S. control module.
4) Disconnect connector cover from connector. 4-4a [T7C2].>
5) Connect connector to A.B.S. control module.
6) Connect the oscilloscope to the A.B.S. control module
connector in accordance with the trouble code.
7) Turn ignition switch ON.
8) Rotate wheels and measure voltage at specified fre-
quency.
NOTE:
When this inspection is completed, the A.B.S. control mod-
ule sometimes memorizes the trouble code 29.
TROUBLE CODE / Connector & terminal:
22 / (P3) No. 23 (+)—No. 21 ()
24 / (P3) No. 22 (+)—No.4()
26 / (P3) No. 24 (+)—No. 26 ()
28 / (P3) No. 8 (+)—No.9()
Specified voltage: 0.12—1 V (When it is 20 Hz.)
B4M0248B
2. CHECK RESISTANCE OF A.B.S. SENSOR.
1) Turn ignition switch OFF.
2) Disconnect connector from A.B.S. sensor.
3) Measure resistance between A.B.S. sensor connector
terminals.
TROUBLE CODE / Connector & terminal:
22 / (B6) No. 1—No. 2
24 / (B15) No. 1—No. 2
26 / (P8) No. 1—No. 2
28 / (P9) No. 1—No. 2
Specified resistance: 0.8—1.2 kΩ
24
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7. Diagnostics Chart with Trouble Code

G4M0700
G4M0701
3. CHECK A.B.S. SENSOR MECHANICAL TROUBLE.
1) Dismount brake as outlined in manual to gain access to
A.B.S. sensor and tone wheel for inspection.
2) Check pole piece and tone wheel for accumulation of
foreign particles. If necessary, remove foreign particles and
clean.
3) Check tone wheel teeth for cracks for deformities. If
necessary, replace tone wheel (No. of teeth: 44) with a new
one.
4) Check tone wheel for looseness.
Tightening torque:
10—16 N⋅m (1.0—1.6 kg-m, 7—12 ft-lb)
5) Measure tone wheel-to-pole piece gap over entire
perimeter of the wheel.
SpecificationsFront wheel Rear wheel
0.9—1.4 mm
(0.035—0.055 in)0.7—1.2 mm
(0.028—0.047 in)
If measurements check out“Not OK”, adjust the gap using
spacers (Part No. 26755AA000). If spacers cannot correct
the gap, replace worn sensor or worn tone wheel.
6) Check hub runout.
Specifications 0.05 mm (0.0020 in)
25
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7. Diagnostics Chart with Trouble Code

E: TROUBLE CODE 29
—FAULTY TONE WHEEL, ETC.—
DIAGNOSIS:

Faulty tone wheel

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

A.B.S. does not operate.
NOTE:
When the wheels turn freely for a long time, such as when
the vehicle is towed or jacked-up, or when steering wheel
is continuously turned all the way, this trouble code may
sometimes occur.
Check tire specifications, tire wear and air
pressure.

OK
Not OK
Replace tire.
1. Check input signal of A.B.S. sensor to
A.B.S. control module side.
Not OK
OK
Check contact of A.B.S. control module connector
terminal.
Not OK OK
Repair A.B.S. control module connector.
Replace A.B.S. control module.
2. Check resistance of A.B.S. sensor.
Not OK
OK
Repair harness/connector.
3. Check A.B.S. sensor mechanical trouble.
Not OK
OK
Replace A.B.S. sensor.
Repair mechanical trouble.
NOTE:
When checking A.B.S. sensor, carefully bend or swing con-
nector and harness to check for improper contact or open
circuits.






26
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7. Diagnostics Chart with Trouble Code

B4M0711A
1. CHECK INPUT SIGNAL OF A.B.S. SENSOR TO
A.B.S. CONTROL MODULE SIDE.
1) Raise all four wheels of ground.
2) Turn ignition switch OFF.
3) Disconnect connector from A.B.S. control module.
4) Disconnect connector cover from connector. 4-4a [T7C2].>
5) Connect connector to A.B.S. control module.
6) Connect the oscilloscope to the A.B.S. control module
connector in accordance with the trouble code.
7) Turn ignition switch ON.
8) Rotate wheels and measure voltage at specified fre-
quency.
NOTE:
When this inspection is completed, the A.B.S. control mod-
ule sometimes memorizes the trouble code 29.
Connector & terminal:
(P3) No. 23 (+)—No. 21 ()
(P3) No. 22 (+)—No.4()
(P3) No. 24 (+)—No. 26 ()
(P3) No. 8 (+)—No.9()
Specified voltage: 0.12—1 V (When it is 20 Hz.)
B4M0248B
2. CHECK RESISTANCE OF A.B.S. SENSOR.
1) Turn ignition switch OFF.
2) Disconnect connector from A.B.S. sensor.
3) Measure resistance between A.B.S. sensor connector
terminals.
Connector & terminal:
(B6) No. 1—No. 2
(B15) No. 1—No. 2
(P8) No. 1—No. 2
(P9) No. 1—No. 2
Specified resistance: 0.8—1.2 kΩ
28
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7. Diagnostics Chart with Trouble Code

G4M0700
G4M0701
3. CHECK A.B.S. SENSOR MECHANICAL TROUBLE.
1) Dismount brake as outlined in manual to gain access to
A.B.S. sensor and tone wheel for inspection.
2) Check pole piece and tone wheel for accumulation of
foreign particles. If necessary, remove foreign particles and
clean.
3) Check tone wheel teeth for cracks for deformities. If
necessary, replace tone wheel (No. of teeth: 44) with a new
one.
4) Check tone wheel for looseness.
Tightening torque:
10—16 N⋅m (1.0—1.6 kg-m, 7—12 ft-lb)
5) Measure tone wheel-to-pole piece gap over entire
perimeter of the wheel.
SpecificationsFront wheel Rear wheel
0.9—1.4 mm
(0.035—0.055 in)0.7—1.2 mm
(0.028—0.047 in)
If measurements check out“Not OK”, adjust the gap using
spacers (Part No. 26755AA000). If spacers cannot correct
the gap, replace worn sensor or worn tone wheel.
6) Check hub runout.
Specifications 0.05 mm (0.0020 in)
29
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7. Diagnostics Chart with Trouble Code

L: TROUBLE CODE 56
—USE OF IMPROPER A.B.S. CONTROL
MODULE SPECIFICATION, OR FAULTY G
SENSOR—
DIAGNOSIS:

Improper A.B.S. control module specification

Faulty G sensor

Faulty G sensor harness and connector
TROUBLE SYMPTOM:

A.B.S. does not operate.

A.B.S. activates faster than specifications when braking
on high“µ”(dry asphalt) road.

Warning light comes on and trouble code“56”is dis-
played approximately 20 seconds after vehicle starts.
Check A.B.S. control module specification.
OK
Not OK
Replace A.B.S. control module.
1. Check continuity in G sensor circuit on A.B.S.
control module side.
Not OK
OK
Faulty A.B.S. control module.
(Replace after inspection of power supply.)
2. Check G sensor.
Not OK
OK
3. Check harness between A.B.S. control module
and G sensor.
Replace G sensor.



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7. Diagnostics Chart with Trouble Code

B4M0610
B4M0281B
1. CHECK CONTINUITY IN G SENSOR CIRCUIT ON
A.B.S. CONTROL MODULE SIDE.
1) Position vehicle on a flat surface.
2) Disconnect connector from A.B.S. control module.
3) Measure resistance between A.B.S. control module
connector terminals.
Connector & terminal / Specified resistance:
(P3) No. 1—No. 13 / 550—670Ω
B4M0353A
2. CHECK G SENSOR.
1) Disconnect G sensor connector.
2) Measure resistance between G sensor terminals.
(Ensure that G sensor is horizontal during measurement.)
Specified resistance:
550—670Ω
48
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7. Diagnostics Chart with Trouble Code

B4M0283B
3. CHECK HARNESS BETWEEN A.B.S. CONTROL
MODULE AND G SENSOR.
1) Turn ignition switch ON.
2) Connect G sensor connector.
3) Measure voltage between connector and body.
Connector & terminal / Specified voltage:
(B23) No. 1—Body / 10—12 V
(P3) No. 13—Body / 10—12 V
NOTE:
When voltage checks out“OK”, replace A.B.S. control
module.
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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