Subaru Legacy IV (2008 year). Manual - part 712

4AT(diag)-69

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

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

(B55) No. 6 — (B11) No. 7:

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 the harness connec-
tor between TCM connector and chassis 
ground.

Connector & terminal

(B55) No. 6 — Chassis ground:

Is the resistance 1 M

: or 

more?

Go to step 3.

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

3

CHECK HIGH CLUTCH DUTY SOLENOID.
Measure the resistance between transmission 
connector receptacle’s terminals.

Connector & terminal

(T4) No. 7 — No. 20:

Is the resistance 2.0 — 6.0 

:? Go to step 4.

Go to step 7.

4

CHECK OUTPUT SIGNAL FROM TCM US-
ING SUBARU SELECT MONITOR.
1) Connect the connectors to TCM and trans-
mission.
2) Lift up the vehicle.
3) Connect the Subaru Select Monitor to data 
link connector.
4) Start the engine, and run the Subaru Select 
Monitor.
5) Start the engine and warm up the engine 
until the ATF temperature exceeds 80°C 
(176°F).

NOTE:
If the ambient temperature is below 0°C (32°F),
drive the vehicle until the ATF reaches its oper-
ating temperature.
6) Read the data of “High Clutch Duty” using 
Subaru Select Monitor.
• High clutch duty solenoid is indicated in “%”.
7) Shift the select lever to “D”, and slowly 
increase vehicle speed to measure at 3rd or 
4th.

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.>

Is the measured value 0%?

Go to step 5.

Go to step 6.

4AT(diag)-70

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

5

CHECK OUTPUT SIGNAL FROM TCM US-
ING SUBARU SELECT MONITOR.
Return the engine to idling speed and shift the 
select lever to “N” range.

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.>

Is the measured value 100%?

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 or con-
nector in TCM and 
transmission.

Go to step 6.

6

CHECK POOR CONTACT.

Is there poor contact in high 
clutch duty solenoid circuit?

Repair the poor 
contact.

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

7

CHECK HIGH CLUTCH DUTY SOLENOID (IN 
TRANSMISSION).
1) Remove the transmission connector from 
bracket.
2) Drain the automatic transmission fluid.

CAUTION:
Do not drain ATF until it cools down.
3) Remove the oil pan, and disconnect the 
control valve body connector.
4) Measure the resistance between high clutch 
duty solenoid connector and transmission 
ground.

Connector & terminal

(AT2) No. 3 — Transmission ground:

Is the resistance 2.0 — 6.0 

:? Go to step 8.

Replace the con-
trol valve body. 
<Ref. to 4AT-56, 
Control Valve 
Body.>

8

CHECK HARNESS CONNECTOR BETWEEN 
HIGH CLUTCH DUTY SOLENOID AND 
TRANSMISSION.
Measure the resistance of harness between 
high clutch duty solenoid and transmission con-
nector.

Connector & terminal

(T4) No. 7 — (AT2) No. 3:

Is the resistance less than 1 

:? Go to step 9.

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

9

CHECK HARNESS CONNECTOR BETWEEN 
HIGH CLUTCH DUTY SOLENOID AND 
TRANSMISSION.
Measure the resistance of harness between 
transmission connector and transmission 
ground.

Connector & terminal

(T4) No. 7 — Transmission ground:

Is the resistance 1 M

: or 

more?

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 or con-
nector in high 
clutch duty sole-
noid and transmis-
sion.

Repair the short 
circuit of harness 
between high 
clutch duty sole-
noid and transmis-
sion connector.

Step

Check

Yes

No

4AT(diag)-71

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

T: DTC P0768 SHIFT SOLENOID “D” ELECTRICAL

DTC DETECTING CONDITION:
The output signal circuit of low & reverse duty solenoid is open or shorted.
TROUBLE SYMPTOM:
Gear is not changed.
WIRING DIAGRAM:

AT-04773

B11

1

2

3 4

5

6 7

8

9

13

14 15

20

19

17

16

10

11 12

18

5

B55

B11

AT 2

T4

6

1

B55

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

AT2

10

9

8

7

6

5

4

3

2

1

TCM

CONTROL VALVE BODY

LOW & 
REVERSE
DUTY
SOLENOID

4AT(diag)-72

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

Step

Check

Yes

No

1

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

Connector & terminal

(B55) No. 5 — (B11) No. 6:

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 CHASSIS GROUND.
Measure the resistance of harness between 
TCM connector and chassis ground.

Connector & terminal

(B55) No. 5 — Chassis ground:

Is the resistance 1 M

: or 

more?

Go to step 3.

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

3

CHECK LOW & REVERSE DUTY SOLENOID.
Measure the resistance between transmission 
connector terminals.

Connector & terminal

(T4) No. 6 — No. 20:

Is the resistance 2.0 — 6.0 

:? Go to step 4.

Go to step 7.

4

CHECK OUTPUT SIGNAL FROM TCM US-
ING SUBARU SELECT MONITOR.
1) Connect all connectors.
2) Connect the Subaru Select Monitor to data 
link connector.
3) Start the engine, and run the Subaru Select 
Monitor.
4) Warm up the transmission until the ATF 
temperature exceeds approximately 80°C 
(176°F).

NOTE:
If the ambient temperature falls below 0°C
(32°F), drive the vehicle until the ATF reaches
its operating temperature.
5) Stop the engine and turn the ignition switch 
to ON (with engine OFF).
6) Shift the select lever to “N” range.
7) Read the data of “L&R/B Duty” using Sub-
aru Select Monitor.
• Low & reverse duty solenoid is indicated in 
“%”.

Is the measured value 100%?

Go to step 5.

Go to step 6.

5

CHECK OUTPUT SIGNAL FROM TCM US-
ING SUBARU SELECT MONITOR.
1) Lift up the vehicle.
2) Shift the select lever to manual mode, and 
then hold it on 1st. Slowly increase the vehicle 
speed up to 15 km/h (9 MPH), and then return 
the accelerator pedal.

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.>
3) Read the data of “L&R/B Duty”.

Is the measured value 55%?

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 or con-
nector in TCM and 
transmission.

Go to step 6.