Subaru Legacy IV (2008 year). Manual - part 701

4AT(diag)-25

AT OIL TEMP Warning Light Display

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK ATF TEMPERATURE WARNING 
LIGHT.
Turn the ignition switch to ON.

Does the ATF temperature 
warning light illuminate?

Go to step 2.

Perform the self-
diagnosis of com-
bination meter.

2

CHECK ATF TEMPERATURE WARNING 
LIGHT.
After the ignition switch is ON, wait for 2 sec-
onds or more.

Does the ATF temperature 
warning light illuminate?

Go to step 3.

Go to step 4.

3

CHECK ATF TEMPERATURE WARNING 
LIGHT.
Start the engine.

Does the ATF temperature 
warning light go off?

Normal. Go back to 
Basic Diagnostic 
Procedure. <Ref. 
to 4AT(diag)-2, 
Basic Diagnostic 
Procedure.>

Go to step 7.

4

CHECK SUBARU SELECT MONITOR COM-
MUNICATION.
Connect the Subaru Select Monitor to data link 
connector.

Is the communication between 
Subaru Select Monitor and 
TCM normal?

Go to step 5.

Check the power 
supply ground cir-
cuit of TCM and 
Subaru Select 
Monitor communi-
cation. <Ref. to 
4AT(diag)-26, 
Diagnostic Proce-
dure for Subaru 
Select Monitor 
Communication.>

5

CHECK TCM.
Display the current data of TCM using Subaru 
Select Monitor.

Is the “Diagnosis Light” output 
signal “ON”?

Go to step 6.

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

6

CHECK BODY INTEGRATED UNIT.
Display current data of the body integrated unit 
using the Subaru Select Monitor. <Ref. to 
LAN(diag)-12, OPERATION, Subaru Select 
Monitor.>

Is the “ATF Temperature Lamp” 
input signal on “Illuminate”?

Replace the com-
bination meter 
assembly. <Ref. to 
IDI-22, Combina-
tion Meter.>

Check DTC of 
body integrated 
unit. <Ref. to 
LAN(diag)-12, 
OPERATION, Sub-
aru Select Moni-
tor.>

7

CHECK TCM.
Display the current data of TCM using Subaru 
Select Monitor. <Ref. to 4AT(diag)-16, OPERA-
TION, Subaru Select Monitor.>

Is the “Diagnosis Light” output 
signal “ON”?

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

Go to step 8.

8

CHECK BODY INTEGRATED UNIT.
Display current data of the body integrated unit 
using the Subaru Select Monitor. <Ref. to 
LAN(diag)-12, OPERATION, Subaru Select 
Monitor.>

Is the “ATF Temperature Lamp” 
input signal on “Illuminate”?

Check DTC of 
body integrated 
unit. Perform the 
diagnosis accord-
ing to DTC. <Ref. 
to LAN(diag)-12, 
OPERATION, Sub-
aru Select Moni-
tor.>

Perform the self-
diagnosis of com-
bination meter. 
<Ref. to IDI-5, 
INSPECTION,
Combination Meter 
System.>

4AT(diag)-26

Diagnostic Procedure for Subaru Select Monitor Communication

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

11.Diagnostic Procedure for Subaru Select Monitor Communication

A: COMMUNICATION FOR INITIALIZING IMPOSSIBLE

DIAGNOSIS:
Defective harness connector
TROUBLE SYMPTOM:
Subaru Select Monitor communication failure
WIRING DIAGRAM:

B40

16

5

7

4

E

1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16

5

6

7

2

1

3

4

29

10 11 12 13 14 15

25

24

16

30

9

8

17 18 19

20
28

21 22 23

32

31

26 27

33

34 35

No. 13

SBF-6

B40

B55

B11

T4

TCM

25

1

2

8

E

E

B11

1

2

3 4

5

6 7

8

9

13

14 15

20

19

17

16

10

11 12

18

19

20

A:

C:

27

26

B134

8

7

6

5

4

3

2

1

22 23

21

20

19

16

15

14

13

12

11

10

9

34 35

33

32

17
30

18
31

29

28

27

26

25

24

B136

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

33 34

29

32

30

31

35

23

22

20

21

B55

E

B134

A:

B136

C:

ECM

C6

A5

36

B21

1 2 3 4 5 6 7 8 9 10 11

12 13 14 15 16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33

34

35

42

43

36

37

38

39

48

49

50

51

52

53

54

40

41

44

45

46

47

B21

E2

AT-04897

CONTROL VALVE BODY

IGNITION

SWITCH

BATTERY

DATA LINK
CONNECTOR

M/B No.

 12

F/B No.

 12

MAIN  SBF

4AT(diag)-27

Diagnostic Procedure for Subaru Select Monitor Communication

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK INSTALLATION OF TCM CONNEC-
TOR.
Turn the ignition switch to OFF.

Is TCM connector connected to 
TCM?

Go to step 2.

Connect the TCM 
connector to TCM.

2

CHECK SUBARU SELECT MONITOR POW-
ER SUPPLY CIRCUIT.
Measure the voltage between data link connec-
tor and chassis ground.

Connector & terminal

(B40) No. 16 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step 3.

Repair harness 
connector between 
the battery and 
data link connec-
tor, and poor con-
tact of the 
connector.

3

CHECK SUBARU SELECT MONITOR 
GROUND CIRCUIT.
1) Disconnect the connectors from ECM.
2) Measure the resistance of harness between 
data link connector and ECM.

Connector & terminal

(B40) No. 4 — (B136) No. 6:
(B40) No. 5 — (B136) No. 6:

Is the resistance less than 1 

:? Go to step 4.

Repair the open 
circuit of harness 
between data link 
connector and 
ECM.

4

CHECK SUBARU SELECT MONITOR 
GROUND CIRCUIT.
Measure the resistance of harness between 
data link connector and chassis ground.

Connector & terminal

(B40) No. 4 — Chassis ground:
(B40) No. 5 — Chassis ground:

Is the resistance 1 M

: or 

more?

Go to step 5.

Repair the short 
circuit of harness 
between data link 
connector and 
ground terminals.

5

CHECK ENGINE GROUND CIRCUIT.
Check the engine ground circuit.

Is the engine ground circuit nor-
mal?

Go to step 6.

Repair ground cir-
cuit of ECM.

6

CHECK COMMUNICATION OF SUBARU SE-
LECT MONITOR.
1) Turn the ignition switch to ON.
2) Using the Subaru Select Monitor, check 
whether communication to transmission system 
can be executed normally.

Is the name of system dis-
played on Subaru Select Moni-
tor?

Go to step 11.

Go to step 7.

7

CHECK COMMUNICATION OF SUBARU SE-
LECT MONITOR.
1) Turn the ignition switch to OFF.
2) Disconnect the TCM connector.
3) Check whether communication to engine 
system can be executed normally.

Is the name of system dis-
played on Subaru Select Moni-
tor?

Go to step 9.

Go to step 8.

8

CHECK COMMUNICATION OF SUBARU SE-
LECT MONITOR.
1) Turn the ignition switch to OFF.
2) Connect the TCM connector.
3) Disconnect the connectors of TPM control 
unit, airbag control module, body integrated 
unit, and ABSCM&H/U.

CAUTION:
When disconnecting the connector from air-
bag control module, always follow the pre-
cautions on AB section. <Ref. to AB-4,
CAUTION, General Description.>
4) Turn the ignition switch to ON.
5) Check whether communication to transmis-
sion system can be executed normally.

Is the name of system dis-
played on Subaru Select Moni-
tor?

Check each control 
module.

Go to step 9.

4AT(diag)-28

Diagnostic Procedure for Subaru Select Monitor Communication

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

9

CHECK HARNESS CONNECTOR BETWEEN 
EACH CONTROL MODULE AND DATA LINK 
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors of TCM, ECM, 
TPM control unit, airbag control module, body 
integrated unit, and ABSCM&H/U.
3) Measure the resistance between TCM con-
nector and chassis ground.

Connector & terminal

(B40) No. 7 — Chassis ground:

Is the resistance 1 M

: or 

more?

Go to step 10.

Check harness 
and connector 
between each con-
trol module and 
data link connec-
tor.

10

CHECK OUTPUT SIGNAL OF TCM.
1) Turn the ignition switch to ON.
2) Measure the voltage between TCM and 
chassis ground.

Connector & terminal

(B40) No. 7 (+) — Chassis ground (–):

Is the voltage 1 V or more?

Check harness 
and connector 
between each con-
trol module and 
data link connec-
tor.

Go to step 11.

11

CHECK HARNESS CONNECTOR BETWEEN 
TCM AND DATA LINK CONNECTOR.
Measure the resistance between TCM connec-
tor and data link connector.

Connector & terminal

(B55) No. 8 — (B40) No. 7:

Is the resistance less than 1 

:? Go to step 12.

Repair the harness 
and connector 
between TCM and 
data link connec-
tor.

12

CHECK INSTALLATION OF TRANSMISSION 
HARNESS CONNECTOR.

Is the transmission harness 
connector connected to bulk-
head harness connector?

Go to step 13.

Connect the bulk-
head harness con-
nector to 
transmission har-
ness connector.

13

CHECK POOR CONTACT IN CONNECTORS. Is there poor contact in control 

module power supply and data 
link connector?

Repair the poor 
contact.

Go to step 14.

14

CHECK POWER SUPPLY OF TCM.
1) Disconnect the connector from TCM.
2) Turn the ignition switch to ON.
3) Measure the voltage between TCM connec-
tor and chassis ground.

Connector & terminal

(B55) No. 27 (+) — Chassis ground (–):
(B55) No. 26 (+) — Chassis ground (–):
(B55) No. 25 (+) — Chassis ground (–):

Is the voltage 10 — 13 V?

Go to step 16.

Go to step 15.

15

CHECK FUSE (NO. 12).
1) Turn the ignition switch to OFF.
2) Remove the fuse (M/B No. 12).

Is the fuse (No. 12) blown out? Replace the fuse 

(No. 12). If the 
replaced fuse (No. 
12) has blown out 
easily, repair short 
circuit of harness 
between fuse (No. 
12) and TCM.

Repair the open 
circuit of harness 
between fuse (No. 
12) and TCM, or 
fuse (No. 12) and 
battery, and poor 
contact of the con-
nector.

16

CHECK IGNITION POWER SUPPLY CIR-
CUIT.
1) Turn the ignition switch to ON (engine OFF).
2) Measure the ignition power supply voltage 
between TCM connector and chassis ground.

Connector & terminal

(B55) No. 1 (+) — Chassis ground (–):
(B55) No. 2 (+) — Chassis ground (–):

Is the voltage 10 — 13 V?

Go to step 18.

Go to step 17.

Step

Check

Yes

No