Subaru Legacy III (2000-2003 year). Service manual — part 755

VDC-56

VDC (DIAGNOSTICS)

DIAGNOSTICS CHART WITH DIAGNOSIS CONNECTOR

M: DTC 28 ABNORMAL ABS SENSOR (ABNORMAL ABS SENSOR SIGNAL)

(REAR LH)

DIAGNOSIS:
• Faulty ABS sensor signal (noise, irregular signal, etc.)
• Faulty harness/connector
TROUBLE SYMPTOM:
• ABS does not operate.
• VDC does not operate.
WIRING DIAGRAM:

VDC00174

F55

F88

B15

B6

2 1

R72

R73

F45

F2

1

2

2

1

7

6

2

1

4
1
3

F88

17

15

12

13

16

14

R

10

L

F45

B62

:

:

F2

B100

:

:

F55

R49

B15

R73

49

19

17

16

14

15

1

55

46

18

1

2

B6

2

1

R72

8

9

11

12

13

VDC CONTROL MODULE

FRONT ABS
SENSOR LH

FRONT ABS

SENSOR RH

LHD

RHD

REAR ABS

SENSOR LH

REAR ABS

SENSOR RH

F87

56 57

59 60

62 63

65

82 83

80

27

28

25

26

23

24

21

22

19

20

17

18

15

16

13

14

11

12

9

10

7

8

5

6

3

4

1

2

54

55

52

53

50

51

81

48

49

46

47

44

45

78

79

76

77

75

42

43

40

41

74

72

73

70

71

39

37

38

35

36

69

67

68

66

33

34

61

64

31

32

29

30

58

F87

: RHD MODEL

:LHD MODEL

R

R

R

L

L

L

1

3

4 5 6

2

1 2

3 4 5

6 7 8 9 10 11 12

1 2 3

4 5 6 7

8 9 10 11 12 13 14 15 16

3 4

1 2

8 9 10 11

12 13 14 15 16 17 18 19 20 21 22 23 24

5 6

7

VDC-57

VDC (DIAGNOSTICS)

DIAGNOSTICS CHART WITH DIAGNOSIS CONNECTOR

Step

Value

Yes

No

1

CHECK INSTALLATION OF ABS SENSOR.

Tightening torque:

32

±±±±

10 N·m (3.3

±±±±

1.0 kgf-m, 24

±±±±

7 ft-lb)

Are the ABS sensor installation bolts tightened
securely?

Tightened securely.

Go to step 2.

Tighten ABS sen-
sor installation
bolts securely.

2

CHECK ABS SENSOR GAP.
Measure tone wheel to pole piece gap over
entire perimeter of the wheel.
Is the measured value within the specified
range?

Front wheel 0.3 - 0.8 mm
(0.012 - 0.031 in) and Rear
wheel 0.44 - 0.94 mm (0.0173 -
0.0370 in)

Go to step 3.

Adjust the gap.

NOTE:
Adjust the gap us-
ing spacer (Part
No. 26755AA000).
If spacers cannot
correct the gap, re-
place worn sensor
or worn tone
wheel.

3

CHECK OSCILLOSCOPE.
Is an oscilloscope available?

Available.

Go to step 4.

Go to step 5.

4

CHECK ABS SENSOR SIGNAL.
1) Raise all four wheels of ground.
2) Turn ignition switch OFF.
3) Remove VDCCM connector cover. <Ref. to

VDC-19, VDCCM Connector Cover.>

4) Connect the oscilloscope to the connector.
5) Turn ignition switch ON.
6) Rotate wheels and measure voltage at

specified frequency. <Ref. to ABS-15,
WAVEFORM, Control Module I/O Signal.>

NOTE:

When this inspection is completed, the VDCCM
sometimes stores the DTC 29.

Connector & terminal

DTC 22 / (F87) No. 14 (+) — No. 15 (

−−−−

):

DTC 24 / (F87) No. 49 (+) — No. 19 (

−−−−

):

DTC 26 / (F87) No. 18 (+) — No. 46 (

−−−−

):

DTC 28 / (F87) No. 16 (+) — No. 17 (

−−−−

):

Is oscilloscope pattern smooth, as shown in
figure?

Smooth pattern.

Go to step 8.

Go to step 5.

5

CHECK CONTAMINATION OF ABS SENSOR
OR TONE WHEEL.
Remove disc rotor from hub in accordance
with diagnostic trouble code.
Is the ABS sensor pole piece or the tone wheel
contaminated by dirt or other foreign matter?

Dirt or foreign matter found.

Thoroughly
remove dirt or
other foreign mat-
ter.

Go to step 6.

6

CHECK DAMAGE OF ABS SENSOR OR
TONE WHEEL.
Are there broken or damaged in the ABS sen-
sor pole piece or the tone wheel?

Broken or damaged.

Replace ABS sen-
sor or tone wheel.
Front <Ref. to
VDC-27, Front
ABS Sensor.> and
<Ref. to VDC-29,
Front Tone
Wheel.> Rear
<Ref. to VDC-28,
Rear ABS Sen-
sor.> and <Ref. to
VDC-30, Rear
Tone Wheel.>

Go to step 7.

VDC-58

VDC (DIAGNOSTICS)

DIAGNOSTICS CHART WITH DIAGNOSIS CONNECTOR

7

CHECK TONE WHEEL RUNOUT.
Measure tone wheel runout.
Is the measured value less than the specified
value?

0.05 mm (0.0020 in)

Go to step 8.

Repair tone wheel.
Front <Ref. to
VDC-29, Front
Tone Wheel.>
Rear <Ref. to
VDC-30, Rear
Tone Wheel.>

8

CHECK RESISTANCE OF ABS SENSOR.
1) Turn ignition switch OFF.
2) Disconnect connector from ABS sensor.
3) Measure resistance between ABS sensor

connector terminals.

Terminal

Front RH No. 1 — No. 2:
Front LH No. 1 — No. 2:
Rear RH No. 1 — No. 2:
Rear LH No. 1 — No. 2:

Is the measured value within the specified
range?

1.0 — 1.5 k

Ω

Go to step 9.

Replace ABS sen-
sor. Front <Ref. to
VDC-27, Front
ABS Sensor.>
Rear <Ref. to
VDC-28, Rear
ABS Sensor.>

9

CHECK GROUND SHORT OF ABS SENSOR.
Measure resistance between ABS sensor and
chassis ground.

Terminal

Front RH No. 1 — Chassis ground:
Front LH No. 1 — Chassis ground:
Rear RH No. 1 — Chassis ground:
Rear LH No. 1 — Chassis ground:

Does the measured value exceed the specified
value?

1 M

Ω

Go to step 10.

Replace ABS sen-
sor. Front <Ref. to
VDC-27, Front
ABS Sensor.>
Rear <Ref. to
VDC-28, Rear
ABS Sensor.>

10

CHECK HARNESS/CONNECTOR BETWEEN
VDCCM AND ABS SENSOR.
1) Connect connector to ABS sensor.
2) Disconnect connector from VDCCM.
3) Measure resistance at VDCCM connector

terminals.

Connector & terminal

DTC 22 / (F87) No. 14 — No. 15:
DTC 24 / (F87) No. 49 — No. 19:
DTC 26 / (F87) No. 18 — No. 46:
DTC 28 / (F87) No. 16 — No. 17:

Is the measured value within the specified
range?

1.0 — 1.5 k

Ω

Go to step 11.

Repair harness/
connector
between VDCCM
and ABS sensor.

11

CHECK GROUND SHORT OF HARNESS.
Measure resistance between VDCCM connec-
tor and chassis ground.

Connector & terminal

DTC 22 / (F87) No. 14 — Chassis
ground:
DTC 24 / (F87) No. 49 — Chassis
ground:
DTC 26 / (F87) No. 18 — Chassis
ground:
DTC 28 / (F87) No. 16 — Chassis
ground:

Does the measured value exceed the specified
value?

1 M

Ω

Go to step 12.

Repair harness/
connector
between VDCCM
and ABS sensor.

Step

Value

Yes

No

VDC-59

VDC (DIAGNOSTICS)

DIAGNOSTICS CHART WITH DIAGNOSIS CONNECTOR

12

CHECK GROUND CIRCUIT OF VDCCM.
Measure resistance between VDCCM and
chassis ground.

Connector & terminal

(F87) No. 1 — Chassis ground:
(F87) No. 55 — Chassis ground:

Is the measured value less than the specified
value?

0.5

Ω

Go to step 13.

Repair VDCCM
ground harness.

13

CHECK POOR CONTACT IN CONNECTORS.
Is there poor contact in connectors between
VDCCM and ABS sensor?

There is poor contact.

Repair connector.

Go to step 14.

14

CHECK SOURCES OF SIGNAL NOISE.
Is the car telephone or the wireless transmitter
properly installed?

Installed properly.

Go to step 15.

Properly install the
car telephone or
the wireless trans-
mitter.

15

CHECK SOURCES OF SIGNAL NOISE.
Are noise sources (such as an antenna)
installed near the sensor harness?

Installed properly.

Install the noise
sources apart from
the sensor har-
ness.

Go to step 16.

16

CHECK SHIELD CIRCUIT.
1) Connect all connectors.
2) Measure resistance between shield con-

nector and chassis ground.

Connector & terminal

RHD model

DTC 22 / (F45) No. 14 — Chassis
ground:
DTC 24 / (F45) No. 17 — Chassis
ground:

LHD model

DTC 22 / (F45) No. 13 — Chassis
ground:
DTC 24 / (F45) No. 10 — Chassis
ground:

Is the measured value less than the speci-
fied value?

NOTE:

For the DTC 26 and 28, Go to step 17.

0.5

Ω

Go to step 17.

Repair shield har-
ness.

17

CHECK VDCCM.
1) Connect all connectors.
2) Erase the memory.
3) Perform inspection mode.
4) Read out the diagnostic trouble code.

Is the same diagnostic trouble code as in
the current diagnosis still being output?

Same DTC indicated.

Replace VDCCM.
<Ref. to VDC-8,
VDC Control Mod-
ule (VDCCM).>

Go to step 18.

18

CHECK ANY OTHER DIAGNOSTIC TROU-
BLE CODES APPEARANCE.
Are other diagnostic trouble codes being out-
put?

Other DTC indicated.

Proceed with the
diagnosis corre-
sponding to the
diagnostic trouble
code.

A temporary noise
interference.

Step

Value

Yes

No