Subaru Legacy III (2000-2003 year). Manual - part 158

EN(H4SO)-244

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK OUTPUT SIGNAL FROM ECM.
1) Turn ignition switch to OFF.
2) Connect test mode connector at the lower 

portion of instrument panel (on the driver's 
side), to the side of the center console box.

3) Turn ignition switch to ON.
4) While operating radiator fan relay, measure 

voltage between ECM and chassis ground.

NOTE:

Radiator fan relay operation can be executed
using Subaru Select Monitor. For procedure,
refer to “Compulsory Valve Operation Check
Mode”.<Ref. to EN(H4SO)-48, Compulsory
Valve Operation Check Mode.>  

Connector & terminal

(B134) No. 14 (+) — Chassis ground (

−−−−

):

(B134) No. 13 (+) — Chassis ground (

−−−−

):

Does the measured value change within 
specified range?

0 - 10 V

Even if MI lights 
up, the circuit has 
returned to a nor-
mal condition at 
this time. In this 
case, repair poor 
contact in ECM 
connector.

Go to step 2.

2

CHECK SHORT CIRCUIT IN RADIATOR FAN 
RELAY CONTROL CIRCUIT.
1) Turn ignition switch to OFF.
2) Remove main fan relay and sub fan relay. 

(with A/C models)

3) Disconnect test mode connector.
4) Turn ignition switch to ON.
5) Measure voltage between ECM and chas-

sis ground.

Connector & terminal

(B134) No. 14 (+) — Chassis ground (

−−−−

):

(B134) No. 13 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Repair battery 
short circuit in radi-
ator fan relay con-
trol circuit.

Go to step 3.

3

CHECK MAIN FAN RELAY.
1) Turn ignition switch to OFF.
2) Remove main fan relay.
3) Measure resistance between main fan relay 

terminals.

Terminal

No. 5 — No. 7:

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

1 

Ω

Replace main fan 
relay.

Go to step 4.

4

CHECK SUB FAN RELAY.
1) Remove sub fan relay.
2) Measure resistance between sub fan relay 

terminals.

Terminal

No. 22 — No. 24

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

1 

Ω

Replace sub fan 
relay.

Go to step 5.

5

CHECK POOR CONTACT.
Check poor contact in ECM connector.
Is there poor contact in ECM connector?

There is poor contact.

Repair poor con-
tact in ECM con-
nector.

Replace ECM.  
<Ref. to 
FU(H4SO)-45, 
Engine Control 
Module.>

EN(H4SO)-245

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

MEMO:

EN(H4SO)-246

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

BF:DTC P0703 — TORQUE CONVERTER/BRAKE SWITCH “B” CIRCUIT —

• DTC DETECTING CONDITION:

• Two consecutive driving cycles with fault

CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode<Ref. to EN(H4SO)-47, OPER-
ATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4SO)-40, OPERATION, Inspection 
Mode.> .
• WIRING DIAGRAM:

EN-01136

B64

B65

B64

1 2

3

2

2

*

1

BRAKE LIGHT

SWITCH

:

B65

3 4

1 2

B55

12

B55

TCM

N

O. 1

6

SBF-2

SBF-1

BATTERY

TO STOP LIGHTS

*

: WITH CRUISE CONTROL

*

1 2 3 4

10 11 12
19 20 21

13

5 6

14 15

7

8

9

16

17

18

22

23

24

EN(H4SO)-247

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK OPERATION OF BRAKE LIGHT.
Does brake light come on when depressing the 
brake pedal?

Brake light comes on.

Go to step 2.

Repair or replace 
brake light circuit.

2

CHECK HARNESS BETWEEN TCM AND 
BRAKE LIGHT SWITCH CONNECTOR.
1) Disconnect connectors from TCM and 

brake light switch.

2) Measure resistance of harness between 

TCM and brake light switch connector.

Connector & terminal

(B55) No. 12 — (B64) No. 2:
(B55) No. 12 — (B65) No. 3 (With cruise 
control):

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

1 

Ω

Go to step 3.

Repair or replace 
harness and con-
nector.

NOTE:
In this case, repair
the following:
• Open circuit in 
harness between 
TCM and brake 
light switch con-
nector
• Poor contact in 
TCM connector
• Poor contact in 
brake light switch 
connector

3

CHECK HARNESS BETWEEN TCM AND 
BRAKE LIGHT SWITCH CONNECTOR.
Measure resistance of harness between TCM 
and chassis ground.

Connector & terminal

(B55) No. 12 — Chassis ground:

Does the measured value exceed the specified 
value?

1 M

Ω

Go to step 4.

Repair ground 
short circuit in har-
ness between 
TCM and brake 
light switch con-
nector.

4

CHECK INPUT SIGNAL FOR TCM.
1) Connect connectors to TCM and brake light 

switch.

2) Measure voltage between TCM and chas-

sis ground.

Connector & terminal

(B55) No. 12 (+) — Chassis ground (

−−−−

):

Is the measured value less than the speci-
fied value when releasing the brake pedal?

1 V

Go to step 5.

Adjust or replace 
brake light switch. 
<Ref. to LI-8, Stop 
Light System.>

5

CHECK INPUT SIGNAL FOR TCM.
Measure voltage between TCM and chassis 
ground.

Connector & terminal

(B55) No. 12 (+) — Chassis ground (

−−−−

):

Is the measured value less than the specified 
value when depressing the brake pedal?

10 V

Go to step 6.

Adjust or replace 
brake light switch.  
<Ref. to LI-8, Stop 
Light System.>

6

CHECK POOR CONTACT.
Check poor contact in TCM connector.
Is there poor contact in TCM connector?

There is poor contact.

Repair poor con-
tact in TCM con-
nector.

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