Subaru Legacy IV (2008 year). Service manual — part 768

5AT(diag)-87

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

AD:DTC P0958 BACKUP LIGHT RELAY CIRCUIT HIGH

DTC DETECTING CONDITION:
Output circuit of the back-up light relay is open or shorted
TROUBLE SYMPTOM:
Back-up light does not illuminate in “R” range.
WIRING DIAGRAM:

13

B55

B226

TCM

IG2 RELAY

No.1

8

E

1

3

2

4

B226

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

10
11

6

5

1

4

2

3

8 9

7

MAIN SBF

SBF-8

B

A

TTER

Y

BACK-UP LIGHT RELAY

BACK-UP LIGHT SYSTEM

AT-04365

5AT(diag)-88

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK DTC OF TCM.

Is DTC of Transmission Range
Sensor Circuit (PRNDL Input)
detected?

Perform the diag-
nosis according to
DTC.

Go to step 2.

2

CHECK HARNESS CONNECTOR BETWEEN
TCM AND BACK-UP LIGHT RELAY.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from TCM and
back-up light relay.
3) Measure the resistance of harness between
TCM connector and back-up light relay connec-
tor.

Connector & terminal

(B55) No. 13 — (B226) No. 4:

Is the resistance less than 1

:? Go to step 3.

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

3

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

Connector & terminal

(B55) No. 13 — 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.

4

CHECK TCM OUTPUT SIGNAL.
1) Turn the ignition switch to ON. (engine OFF)
2) Shift the select lever to “P” range.
3) Measure the voltage between TCM connec-
tor and chassis ground.

Connector & terminal

(B55) No. 13 (+) — Chassis ground (–):

Is the voltage 8 V or more?

Go to step 5.

Replace the TCM.
<Ref. to 5AT-60,
Transmission Con-
trol Module
(TCM).>

5

CHECK TCM OUTPUT SIGNAL.
1) Set the select lever to “R” range.
2) Measure the voltage between TCM connec-
tor and chassis ground.

Connector & terminal

(B55) No. 13 (+) — Chassis ground (–):

Is the voltage 1 V or less?

Go to step 6.

Replace the TCM.
<Ref. to 5AT-60,
Transmission Con-
trol Module
(TCM).>

6

CHECK INPUT VOLTAGE FOR BACK-UP
LIGHT RELAY.
Measure the voltage between back-up light
relay and chassis ground.

Is the voltage 10 — 13 V?

Replace the back-
up light relay.

Check open or
short circuit of har-
ness between fuse
(No. 18) and back-
up light relay.

5AT(diag)-89

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

AE:DTC P1706 AT VEHICLE SPEED SENSOR CIRCUIT MALFUNCTION

(REAR WHEEL)

DTC DETECTING CONDITION:
Input signal circuit of TCM is open or shorted.
TROUBLE SYMPTOM:
• Shifting quality malfunction
• Tight corner braking phenomenon occurs.
WIRING DIAGRAM:

Step

Check

Yes

No

1

CHECK TCM I/O SIGNAL.
Check the power supply and ground I/O signals.
<Ref. to 5AT(diag)-14, ELECTRICAL SPECIFI-
CATION, Transmission Control Module (TCM) I/
O Signal.>

Is TCM I/O signal OK?

Go to step 2.

Repair the open or
short circuit for
power supply and
ground.

2

CHECK TCM AND TRANSMISSION HAR-
NESS CONNECTOR.
1) Disconnect the connectors from TCM and
transmission.
2) Measure the resistance of harness between
TCM connector and transmission connector.

Connector & terminal

(B54) No. 23 — (B12) No. 5:
(B54) No. 27 — (B11) No. 7:
(B54) No. 16 — (B11) No. 2:

Is the resistance less than 1

:? Go to step 3.

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

3

CHECK TCM AND TRANSMISSION HAR-
NESS CONNECTOR.
Measure the resistance of harness between
TCM connector and chassis ground.

Connector & terminal

(B54) No. 23 — Chassis ground:
(B54) No. 27 — Chassis ground:
(B54) No. 16 — 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-04366

B54

27

7

AT4

TCM

16

2

B11

23

5

1 2

5

6 7

8

13

14 15

16

9 10

11 12

3 4

17 18

19 20

AT4

1

3

1

2

B54

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

B11

T4

B12

T3

B12

8

7

6

5

4

3

2

1

2 3

REAR VEHICLE SPEED SENSOR

5AT(diag)-90

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

4

CHECK TCM POWER SUPPLY OUTPUT.
1) Connect the connector to the TCM. (Trans-
mission connector is disconnected)
2) Turn the ignition switch to ON. (engine OFF)
3) Measure the voltage between transmission
connector and chassis ground.

Connector & terminal

(B11) No. 7 (+) — Chassis ground (–):

Is the voltage 10 — 13 V?

Go to step 5.

Replace the TCM.
<Ref. to 5AT-60,
Transmission Con-
trol Module
(TCM).>

5

CHECK INPUT CIRCUIT OF TCM TURBINE
SPEED SENSOR.
Measure the voltage variation between TCM
connector terminals.

Connector & terminal

(B12) No. 5 (+) — (B11) No. 2 (–):

Is the voltage 4 — 6 V?

Go to step 7.

Go to step 6.

6

CHECK HARNESS ASSEMBLY (TURBINE
SPEED SENSOR GROUND).
Check the installing condition of ground con-
necting harness (used for both of turbine speed
sensor 1, rear vehicle speed sensor).

Is the ground connecting har-
ness installed to transmission
body correctly, or the harness
and connector terminals not
damaged?

Go to step 7.

When the poor
installation of
ground connecting
harness, install it
securely.
Replace the trans-
mission assembly
when the harness
is damaged. <Ref.
to 5AT-39, Auto-
matic Transmis-
sion Assembly.>

7

CHECK INPUT SIGNAL FOR TCM USING
SUBARU SELECT MONITOR.
1) Connect all connectors.
2) Lift up the vehicle.

NOTE:
Raise all wheels off the floor.
3) Start the engine, and drive the vehicle.
4) Read the current data of rear wheel speed
using Subaru Select Monitor. <Ref. to
5AT(diag)-18, OPERATION, Subaru Select
Monitor.>

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 value of the rear
wheel speed depending on the
acceleration and deceleration
of the vehicle?

Even if the AT OIL
TEMP light blinks,
the system is in
normal condition.
A temporary poor
contact of connec-
tor or harness may
be the cause.
Repair poor con-
tact of harness in
ATF temperature
sensor and trans-
mission connector.

Replace the trans-
mission harness.

Step

Check

Yes

No