Subaru Legacy III (2000-2003 year). Manual - part 760

VDC-76

VDC (DIAGNOSTICS)

DIAGNOSTICS CHART WITH DIAGNOSIS CONNECTOR

AB:DTC 42 SOURCE VOLTAGE IS ABNORMAL.

DIAGNOSIS:
• Power source voltage of the VDCCM is low.
TROUBLE SYMPTOM:
• ABS does not operate.
• VDC does not operate.
WIRING DIAGRAM:

VDC00144

VDC CONTROL MODULE

1

55

28

F87

SBF-1

GENERATOR

SBF-4

IGNITION 
SWITCH

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

BATTERY

NO

. 18 15A

VDC-77

VDC (DIAGNOSTICS)

DIAGNOSTICS CHART WITH DIAGNOSIS CONNECTOR

Step

Value

Yes

No

1

CHECK GENERATOR.
1) Start engine.
2) Idling after warm-up.
3) Measure voltage between generator B ter-

minal and chassis ground.

Terminal

Generator B terminal — Chassis 
ground:

Is the measured value within the specified 
range?

10 — 15 V

Go to step 2.

Repair generator.

2

CHECK BATTERY TERMINAL.
Turn ignition switch to OFF.
Are the positive and negative battery terminals 
tightly clamped?

Clamped securely.

Go to step 3.

Tighten the clamp 
of terminal.

3

CHECK INPUT VOLTAGE OF VDCCM.
1) Disconnect connector from VDCCM.
2) Run the engine at idle.
3) Measure voltage between VDCCM connec-

tor and chassis ground.

Connector & terminal

(F87) No. 28 (+) — Chassis ground (

−−−−

):

Is the measured value within the specified 
range?

10 — 15 V

Go to step 4.

Repair harness 
connector 
between battery, 
ignition switch and 
VDCCM.

4

CHECK GROUND CIRCUIT OF VDCCM.
1) Turn ignition switch to OFF.
2) Measure resistance between VDCCM con-

nector and chassis ground.

Connector & terminal

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

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

0.5 

Ω

Go to step 5.

Repair VDCCM 
ground harness.

5

CHECK POOR CONTACT IN CONNECTORS.
Is there poor contact in connectors between 
generator, battery and VDCCM?

There is poor contact.

Repair connector.

Go to step 6.

6

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 7.

7

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 poor 
contact.

VDC-78

VDC (DIAGNOSTICS)

DIAGNOSTICS CHART WITH DIAGNOSIS CONNECTOR

AC:DTC 43 FAULTY VDCCM — ECM COMMUNICATION LINE

DIAGNOSIS:
• AET communication line is broken or short circuited.
• AEB communication line is broken or short circuited.
• AEC communication line is broken or short circuited.
TROUBLE SYMPTOM:
• VDC does not operate.
WIRING DIAGRAM:

C8

C7

C2

C8

C7

LH4

RH4

WO

C2

B5

A12

OO

B18

A4

B6

H6

A11

VDC

CONTROL

MODULE

AET

AEB

AEC

5

7

R

21

43

8

6

1

4

L

2

F87

F96

B255

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

B135

ENGINE

CONTROL

MODULE

B134

B135

A:

:

B:

:

H6

RH4 WO

B136

C:

: LH4

OO

RH4

B:

: RH4 WO

: LH4 RH4 OO

B134

A:

: H6

5 6 7

8

2

1

9

4

3

10

24

22 23

25

11 12 13 14 15

26

27 28

16 17 18 19

20 21

1 2 3 4

10 11 12

19 20 21

13

5

6

14 15

7

8 9

16 17

18

22

1 2 3

4 5 6

7 8 9 10 11 12 13 14

F96

L

:

F96

R

:

1 2 3 4

5 6 7 8 9

10 11 12 13 14 15 16 17 18 19 20

VDC00175

C: B136

3

4

1 2

8 9 10 11 12 13 14

15 16 17 18 19 20

21 22 23 24

5 6

7

: 4 CYLINDER ENGINE RHD MODEL

: 4 CYLINDER ENGINE LHD MODEL

RH4

LH4

: 4 CYLINDER ENGINE

: 6 CYLINDER ENGINE

H4

H6

: RHD MODEL

: LHD MODEL

R

L

: WITHOUT OBD MODEL

: WITH OBD MODEL

OO

WO

VDC-79

VDC (DIAGNOSTICS)

DIAGNOSTICS CHART WITH DIAGNOSIS CONNECTOR

Step

Value

Yes

No

1

CHECK HARNESS/CONNECTOR BETWEEN 
VDCCM AND ECM.
1) Turn ignition switch to OFF.
2) Disconnect connector from VDCCM.
3) Disconnect connector from ECM.
4) Measure resistance between VDCCM con-

nector and ECM.

Connector & terminal

H4 engine RHD without OBD model

(F87) No. 21 — (B136) No. 7:
(F87) No. 43 — (B136) No. 8:
(F87) No. 8 — (B136) No. 2:

H4 engine RHD with OBD model

(F87) No. 21 — (B135) No. 6:
(F87) No. 43 — (B135) No. 5:
(F87) No. 8 — (B135) No. 18:

H4 engine LHD model

(F87) No. 21 — (B136) No. 7:
(F87) No. 43 — (B136) No. 8:
(F87) No. 8 — (B136) No. 2:

H6 engine model

(F87) No. 21 — (B134) No. 12:
(F87) No. 43 — (B134) No. 4:
(F87) No. 8 — (B134) No. 11:

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

0.5 

Ω

Go to step 2.

Repair harness/
connector 
between VDCCM 
and ECM.

2

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

Connector & terminal

(F87) No. 21 — Chassis ground:
(F87) No. 43 — Chassis ground:
(F87) No. 8 — Chassis ground:

Does the measured value exceed the specified 
value?

1 M

Ω

Go to step 3.

Repair harness/
connector 
between VDCCM 
and ECM.

3

CHECK BATTERY SHORT OF HARNESS.
Measure voltage between VDCCM connector 
and chassis ground.

Connector & terminal

(F87) No. 21 (+) — Chassis ground (

−−−−

):

(F87) No. 43 (+) — Chassis ground (

−−−−

):

(F87) No. 8 (+) — Chassis ground (

−−−−

):

Is the measured value less than the specified 
value?

0.5 V

Go to step 4.

Repair harness/
connector 
between VDCCM 
and ECM.

4

CHECK BATTERY SHORT OF HARNESS.
1) Turn ignition switch to ON.
2) Measure voltage between VDCCM connec-

tor and chassis ground.

Connector & terminal

(F87) No. 21 (+) — Chassis ground (

−−−−

):

(F87) No. 43 (+) — Chassis ground (

−−−−

):

(F87) No. 8 (+) — Chassis ground (

−−−−

):

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

1 V

Go to step 5.

Repair harness/
connector 
between VDCCM 
and ECM.