Subaru Legacy III (2000-2003 year). Manual - part 597

AT-122

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE FOR NO-DIAGNOSTIC TROUBLE CODE (DTC)

B: CHECK FWD SWITCH.

DIAGNOSIS:
• LED does not come on even if FWD switch is ON.
• FWD switch circuit is open or shorted.
WIRING DIAGRAM:

AT-00786

BATTERY

LH RH

No.5

IGNITION

RELAY

FWD

i10

i1

B36

A:

B55

B:

B56

TCM

C:

C:

i12

F67

COMBINATION
METER

E

FWD
SWITCH

36
35

B55

B56

1 2 3 4

10 11 12
19 20 21

13

5 6

14 15

7

8

9

16

17

18

22

23

24

1 2 3 4

10 11 12
19 20 21

13

5 6

14 15

7

8

9

16

17

18

22

23

24

E

C3

A16

O5

F45

B62

6

8

C2

B20

i10

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

i12

1 2 3

4 5 6

7 8 9 10 11 12 13 14

B36

B4 B5 B6

A4 A5 A6

C5 C6

F6

D4 D5 D6

F1

H1

C4

G6

G1

C2

K1

M1 M2

K6

L1

D1 D2

A1 A2
B1 B2

I6

J6

L2

I1

J1

H6

M4 M5 M6

L4 L5 L6 

N5 N6

O4 O5 O6

N4

P4 P5

N2

O1 O2

P1 P2

N3

O3

P3

P6

A3

B3

C3

E4 E5 E6

E1 E2

1

2

3

4

31

30

34

33

32

28

25

27

26

29

21

20

24

23

22

6

5

7

8
9

18

15

17

16

19

11

10

35

36

F67

14

13

12

: LHD MODEL

LH

: RHD MODEL

RH

1

2 3

4 5 6 7 8

F45

RHD

:

LHD

:

F45

1 2 3

4 5 6 7

8 9 10 11 12 13 14 15 16

AT-123

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE FOR NO-DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK FWD SWITCH.
When fuse is inserted to FWD switch, does 
LED light up?

LED lights up.

Go to step CHECK 
BRAKE 
SWITCH.<Ref. to 
AT-125, CHECK 
BRAKE SWITCH., 
Diagnostic Proce-
dure for No-diag-
nostic Trouble 
Code (DTC).>

Go to step 2.

2

CHECK FWD INDICATOR LIGHT.
1) Turn ignition switch to OFF.
2) Remove combination meter.
3) Remove FWD indicator light bulb from 

combination meter.
Is FWD indicator light bulb OK?

Bulb is normal.

Go to step 3.

Replace FWD indi-
cator light bulb. 
<Ref. to IDI-14, 
Combination 
Meter Assembly.>

3

CHECK HARNESS CONNECTOR BETWEEN 
TCM AND FWD SWITCH.
1) Turn ignition switch to OFF.
2) Disconnect connector from TCM and FWD 

switch.

3) Measure resistance of harness between 

TCM and FWD switch connector.

Connector & terminal

(B55) No. 20 — (F67) No. 36:

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

1 

Ω

Go to step 4.

Repair open circuit 
in harness 
between TCM and 
FWD switch con-
nector.

4

CHECK HARNESS CONNECTOR BETWEEN 
TCM AND FWD SWITCH.
Measure resistance of harness connector 
between TCM and body to make sure that cir-
cuit does not short.

Connector & terminal

(B55) No. 20 — Chassis ground:

Does the measured value exceed the specified 
value?

1 M

Ω

Go to step 5.

Repair short circuit 
in harness 
between TCM and 
FWD switch con-
nector.

5

CHECK HARNESS CONNECTOR BETWEEN 
FWD SWITCH AND CHASSIS GROUND.
Measure resistance of harness between FWD 
switch and chassis ground.

Connector & terminal

(F67) No. 35 — Chassis ground:

Is the measured value less than the specified 
value?

1 

Ω

Go to step 6.

Repair open circuit 
in harness 
between FWD 
switch connector 
and chassis 
ground.

6

CHECK INPUT SIGNAL FOR TCM.
1) Turn ignition switch to OFF.
2) Connect connector to TCM and FWD 

switch.

3) Turn ignition switch to ON.
4) Measure signal voltage for TCM while 

installing the fuse to FWD switch connec-
tor.

Connector & terminal

(B55) No. 20 (+) — Chassis ground (

−−−−

):

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

1 V

Go to step 7.

Go to step 11.

AT-124

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE FOR NO-DIAGNOSTIC TROUBLE CODE (DTC)

7

CHECK INPUT SIGNAL FOR TCM.
Measure signal voltage for TCM while remov-
ing the fuse from FWD switch connector.

Connector & terminal

(B55) No. 20 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the specified 
value?

9 V 

Go to step 8.

Replace TCM. 
<Ref. to AT-76, 
Transmission Con-
trol Module 
(TCM).>

8

CHECK HARNESS CONNECTOR BETWEEN 
TCM AND COMBINATION METER.
1) Turn ignition switch to OFF.
2) Disconnect connector from TCM and com-

bination meter.

3) Measure resistance of harness between 

TCM and diagnosis connector.

Connector & terminal

(B56) No. 2 — (i10) No. 16:

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

1 

Ω

Go to step 9.

Repair open circuit 
in harness 
between TCM and 
combination meter 
and poor contact 
in coupling con-
nector.

9

CHECK HARNESS CONNECTOR BETWEEN 
TCM AND COMBINATION METER.
Measure resistance of harness connector 
between TCM and chassis ground to make 
sure that circuit does not short.

Connector & terminal

(B56) No. 2 — Chassis ground:

Does the measured value exceed the specified 
value?

1 M

Ω

Go to step 10.

Repair short circuit 
in harness 
between TCM and 
combination meter 
connector.

10

CHECK OUTPUT SIGNAL EMITTED FROM 
TCM.
1) Turn ignition switch to OFF.
2) Connect connector to TCM and combina-

tion meter.

3) Turn ignition switch to ON.
4) Measure signal voltage for TCM while 

installing and removing the fuse to FWD 
switch connector.

Connector & terminal

(B56) No. 2 — Chassis ground:

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

1 V

Go to step 11.

Go to step 12.

11

CHECK OUTPUT SIGNAL EMITTED FROM 
TCM.
Measure signal voltage for TCM while remov-
ing the fuse from FWD switch connector.

Connector & terminal

(B56) No. 2 — Chassis ground:

Does the measured value exceed the specified 
value?

9 V

Go to step 12.

Replace TCM. 
<Ref. to AT-76, 
Transmission Con-
trol Module 
(TCM).>

12

CHECK POOR CONTACT.
Is there poor contact in FWD switch circuit?

There is poor contact.

Repair poor con-
tact.

Replace TCM. 
<Ref. to AT-76, 
Transmission Con-
trol Module 
(TCM).>

Step

Value

Yes

No

AT-125

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE FOR NO-DIAGNOSTIC TROUBLE CODE (DTC)

C: CHECK BRAKE SWITCH.

D: CHECK ABS SWITCH.

E: CHECK CRUISE CONTROL SWITCH.

Step

Value

Yes

No

1

CHECK BRAKE SWITCH.
When the brake pedal is depressed, does LED 
light up?

LED lights up.

Go to step CHECK 
ABS SWITCH. 
<Ref. to AT-125, 
CHECK ABS 
SWITCH., Diag-
nostic Procedure 
for No-diagnostic 
Trouble Code 
(DTC).>

Check brake 
switch circuit. 
<Ref. to WI-92, A/
T Control Sys-
tem.>

Step

Value

Yes

No

1

CHECK ABS SWITCH.
Does the LED of ABS switch light up?

LED lights up.

Check ABS switch 
circuit. <Ref. to 
ABS-118, DTC 44 
ABS-AT CON-
TROL (NON CON-
TROLLED), 
Diagnostics Chart 
with Subaru Select 
Monitor.> and 
<Ref. to ABS-120, 
DTC 44 ABS-AT 
CONTROL (CON-
TROLLED), Diag-
nostics Chart with 
Subaru Select 
Monitor.>

Go to step CHECK 
CRUISE CON-
TROL SWITCH. 
<Ref. to AT-125, 
CHECK CRUISE 
CONTROL 
SWITCH., Diag-
nostic Procedure 
for No-diagnostic 
Trouble Code 
(DTC).>

Step

Value

Yes

No

1

CHECK CRUISE CONTROL SWITCH.
When cruise control is set, does LED light up?

LED lights up.

Go to step CHECK 
KICK-DOWN 
SWITCH. <Ref. to 
AT-126, CHECK 
KICK–DOWN 
SWITCH., Diag-
nostic Procedure 
for No-diagnostic 
Trouble Code 
(DTC).>

Check cruise con-
trol. <Ref. to CC-
12, Diagnostics 
Chart with Symp-
tom.>