Subaru Legacy IV (2008 year). Manual - part 707

4AT(diag)-49

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

F: DTC P0720 OUTPUT SPEED SENSOR CIRCUIT

DTC DETECTING CONDITION:
• The vehicle speed signal is abnormal.
• The harness connector between TCM and front vehicle speed sensor is shorted or open.
TROUBLE SYMPTOM:
Driving performance is poor.
WIRING DIAGRAM:

Step

Check

Yes

No

1

CHECK HARNESS CONNECTOR BETWEEN 
TCM AND TRANSMISSION.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from TCM and 
transmission.
3) Measure the resistance of harness between 
TCM connector and transmission connector.

Connector & terminal

(B54) No. 27 — (B11) No. 14:

Is the resistance less than 1 

:? Go to step 2.

Repair the open 
circuit of harness 
between TCM and 
transmission con-
nector.

2

CHECK HARNESS CONNECTOR BETWEEN 
TCM AND TRANSMISSION.
Measure the resistance of harness between 
TCM connector and transmission connector.

Connector & terminal

(B54) No. 16 — (B11) No. 18:

Is the resistance less than 1 

:? Go to step 3.

Repair the open 
circuit of harness 
between TCM and 
transmission con-
nector, and poor 
contact of the con-
nector.

3

CHECK HARNESS CONNECTOR BETWEEN 
TCM AND TRANSMISSION.
Measure the resistance of harness between 
TCM connector and transmission connector.

Connector & terminal

(B54) No. 27 — Chassis ground:

Is the resistance 1 M

: or 

more?

Go to step 4.

Repair the short 
circuit of harness 
between TCM and 
transmission con-
nector.

AT-04332

18

14

B11

T4

27

B11

TCM

B54

B53

16

B53

*

*

*

B54

*

1 2

5

6 7

8

13

14 15

16

9 10

11 12

3 4

17 18

19 20

9

8

7

6

5

4

3

2

1

10

11 12 13 14 15 16 17 18 19 20

16

10 11 12 13 14 15

25

24

30

9

8

7

17 18 19 20
28

21 22 23

29

32

31

1

2

3

4

5

6

27

26

33 34 35

JOINT
CONNECTOR

: TERMINAL No. OPTIONAL 
  ARRANGEMENT 
  AMONG 1, 11  AND 12

FRONT VEHICLE
SPEED SENSOR

4AT(diag)-50

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

4

CHECK HARNESS CONNECTOR BETWEEN 
TCM AND TRANSMISSION.
Measure the resistance of harness between 
TCM connector and transmission connector.

Connector & terminal

(B54) No. 16 — Chassis ground:

Is the resistance 1 M

: or 

more?

Go to step 5.

Repair the short 
circuit of the har-
ness between 
TCM and transmis-
sion connector, 
and poor contact of 
connector.

5

CHECK FRONT VEHICLE SPEED SENSOR.
Measure the resistance between transmission 
connector receptacle’s terminals.

Connector & terminal

(T4) No. 14 — No. 18:

Is the resistance 450 — 650 

:? Go to step 6.

Replace the front 
vehicle speed sen-
sor. <Ref. to 4AT-
49, Front Vehicle 
Speed Sensor.>

6

CHECK INPUT SIGNAL FOR TCM USING 
SUBARU SELECT MONITOR.
1) Connect all connectors.
2) Connect the Subaru Select Monitor to data 
link connector.
3) Lift up the vehicle.
4) Turn the ignition switch to ON and run the 
Subaru Select Monitor.
5) Start the engine.
6) Read the data of “Front Wheel Speed” using 
Subaru Select Monitor.
• Compare the speedometer with Subaru 
Select Monitor indications.
• Vehicle speed is indicated in “km/h” or “MPH”
7) Slowly increase the vehicle speed to 60 km/
h (37 MPH).

NOTE:
The speed difference between front and rear
wheels may illuminate the ABS warning light,
but this does not indicate a malfunction. When
AT control diagnosis is finished, perform the
ABS or VDC clear memory of on-board diag-
nostics system. <Ref. to ABS(diag)-20, Clear
Memory Mode.> <Ref. to VDC(diag)-23, Clear
Memory Mode.>

Does the speedometer indica-
tion increase as the Subaru 
Select Monitor front wheel 
speed data increases?

Even if the ATF 
temperature warn-
ing light blinks, the 
circuit is in normal 
condition at this 
time. A temporary 
poor contact of 
connector or har-
ness may be the 
cause. Repair the 
harness in of front 
vehicle speed sen-
sor circuit.

Go to step 7.

7

CHECK POOR CONTACT.

Is there poor contact in front 
vehicle speed sensor circuit?

Repair the poor 
contact.

Replace the TCM. 
<Ref. to 4AT-61, 
Transmission Con-
trol Module 
(TCM).>

Step

Check

Yes

No

4AT(diag)-51

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

G: DTC P0724 BRAKE SWITCH CIRCUIT HIGH

DTC DETECTING CONDITION:
Brake switch malfunction, open input signal circuit
TROUBLE SYMPTOM:
Gear is not shifted down when driving a down hill.
WIRING DIAGRAM:

1

*

2

*

B159

2

1

3 4
8 9

7

6

5

B280

B281

C:

B:

B159

B280

B:

B281

C:

C23

B20

B30

3

5

9

M

AIN SBF

SBF-2

N

o

.8

E

18

17

TCM

B54

B365

2

4

3

B65

1

2

3

4

B65

B365

9

8

7

6

5

4

3

2

1

10

11 12 13 14 15 16 17 18 19

B225

1

*

2

*

1

*

2

*

7.5A

B54

B225

13
14

15 16

17

27

24

25
26

20

21
22

23

29
30

31

28

32

35

33
34

37
38

39

36

40

8

9

10

11 12

1

2

5

3

4

7

6

19

18

CAN JOINT 
CONNECTOR

20

5

4

6 7

8

2

1

9

3

10

22

23

11 12 13 14 15

24 25

26 27

16 17 18

28 29

19 20

21

30

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

16

10 11 12 13 14 15

25

24

30

9

8

7

17 18 19 20
28

21 22 23

29

32

31

1

2

3

4

5

6

27

26

33 34 35

AT-04331

: TERMINAL No. OPTIONAL 
  ARRANGEMENT 
  AMONG 1, 2, 3, 11, 12  AND 13
: TERMINAL No. OPTIONAL 
  ARRANGEMENT 
  AMONG 8, 9, 10, 18, 19  AND 20

BODY INTEGRATED UNIT

FUSE & RELAY 
BOX (F/B)

FUSE
(RELAY BLOCK)

B

A

TTER

Y

STOP LIGHT 
SWITCH

(BLACK)

4AT(diag)-52

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK DTC.

Is DTC of CAN communication 
displayed?

Perform the diag-
nosis according to 
DTC.

Go to step 2.

2

CHECK BODY INTEGRATED UNIT.
1) Turn the ignition switch to OFF.
2) Connect the Subaru Select Monitor to data 
link connector.
3) Turn the ignition switch to ON. (engine OFF)
4) Run the Subaru Select Monitor.
5) Read the data of “Stop Light Switch” using 
Subaru Select Monitor. <Ref. to LAN(diag)-12, 
OPERATION, Subaru Select Monitor.>

Is OFF displayed?

Go to step 3.

Go to step 4.

3

CHECK TCM.
Read the data of “Stop Light Switch” using Sub-
aru Select Monitor. <Ref. to 4AT(diag)-16, 
OPERATION, Subaru Select Monitor.>

Is OFF displayed?

A temporary poor 
contact of connec-
tor or harness may 
be the cause. 
Check the poor 
contact.

Replace the TCM. 
<Ref. to 4AT-61, 
Transmission Con-
trol Module 
(TCM).>

4

CHECK BODY INTEGRATED UNIT INPUT 
SIGNAL.
1) Disconnect the harness connector of body 
integrated unit.
2) Measure the voltage of harness between 
body integrated unit and stop light switch.

Connector & terminal

(B281) No. 23 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step 5.

Go to step 7.

5

CHECK STOP LIGHT SWITCH.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from stop light 
switch.
3) Measure the resistance of harness between 
stop light switch connectors.

Terminals

No. 2 — No. 3:

Is the resistance 1 M

: or 

more?

Go to step 6.

Replace the stop 
light switch.

6

CHECK HARNESS CONNECTOR BETWEEN 
BODY INTEGRATED UNIT AND STOP LIGHT 
SWITCH.
1) Turn the ignition switch to ON.
2) Measure the voltage of harness between 
the body integrated unit and chassis ground.

Connector & terminal

(B281) No. 23 (+) — Chassis ground (–):

Is the voltage less than 1 V?

Go to step 7.

Repair the short 
circuit of harness 
between TCM and 
stop light switch.

7

CHECK POOR CONTACT.

Is there poor contact in input 
signal of brake switch?

Repair the poor 
contact.

Check the body 
integrated unit.