Subaru Legacy III (2000-2003 year). Manual - part 160

EN(H4SO)-252

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

BK:DTC P0741 — TORQUE CONVERTER CLUTCH CIRCUIT PERFORMANCE 

OR STUCK OFF —

• DTC DETECTING CONDITION:

• Two consecutive driving cycles with fault

• TROUBLE SYMPTOM:

• No lock-up (after engine warm-up)
• No shift or excessive tight corner “braking”

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.> .

Step

Value

Yes

No

1

CHECK ANY OTHER DTC ON DISPLAY.
Is any other DTC displayed?

DTC indicated.

Inspect the rele-
vant DTC using 
“List of Diagnostic 
Trouble Code 
(DTC)”. <Ref. to 
EN(H4SO)-83, List 
of Diagnostic 
Trouble Code 
(DTC).>

Go to step 2.

2

CHECK LOCK-UP DUTY SOLENOID CIR-
CUIT.
Check lock-up duty solenoid circuit.
Is there any trouble in lock-up duty solenoid 
circuit?
 <Ref. to AT-96, DTC 77 LOCK-UP DUTY 
SOLENOID, Diagnostic Procedure with Diag-
nostic Trouble Code (DTC).>

There is a fault.

Repair or replace 
lock-up duty sole-
noid circuit.

Go to step 3.

3

CHECK THROTTLE POSITION SENSOR 
CIRCUIT.
Check throttle position sensor circuit. 
Is there any trouble in throttle position sensor 
circuit?
<Ref. to AT-52, DTC 31 THROTTLE POSI-
TION SENSOR, Diagnostic Procedure with 
Diagnostic Trouble Code (DTC).>

There is a fault.

Repair or replace 
throttle position 
sensor circuit.

Go to step 4.

4

CHECK TORQUE CONVERTER TURBINE 
SPEED SENSOR CIRCUIT.
Check torque converter turbine speed sensor 
circuit.
Is there any trouble in torque converter turbine 
speed sensor circuit?
 <Ref. to AT-64, DTC 36 TORQUE CON-
VERTER TURBINE SPEED SENSOR, Diag-
nostic Procedure with Diagnostic Trouble 
Code (DTC).>

There is a fault.

Repair or replace 
torque converter 
turbine speed sen-
sor circuit.

Go to step 5.

5

CHECK ENGINE SPEED INPUT CIRCUIT.
Check engine speed input circuit.
Is there any trouble in engine speed input cir-
cuit?
 <Ref. to AT-42, DTC 11 ENGINE SPEED 
SIGNAL, Diagnostic Procedure with Diagnostic 
Trouble Code (DTC).>

There is a fault.

Repair or replace 
engine speed 
input circuit.

Go to step 6.

EN(H4SO)-253

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

6

CHECK INHIBITOR SWITCH CIRCUIT.
Check inhibitor switch circuit. 
Is there any trouble in inhibitor switch circuit?
<Ref. to AT-132, CHECK INHIBITOR 
SWITCH., Diagnostic Procedure for No-diag-
nostic Trouble Code (DTC).>

There is a fault.

Repair or replace 
inhibitor switch cir-
cuit.

Go to step 7.

7

CHECK BRAKE LIGHT SWITCH CIRCUIT.
Check brake light switch circuit.
Is there any trouble in brake light switch cir-
cuit?
 <Ref. to AT-125, CHECK BRAKE SWITCH., 
Diagnostic Procedure for No-diagnostic Trou-
ble Code (DTC).>

There is a fault.

Repair or replace 
brake light switch 
circuit.

Go to step 8.

8

CHECK ATF TEMPERATURE SENSOR CIR-
CUIT.
Check ATF temperature sensor circuit. 
Is there any trouble in ATF temperature sensor 
circuit?
<Ref. to AT-48, DTC 27 ATF TEMPERATURE 
SENSOR, Diagnostic Procedure with Diagnos-
tic Trouble Code (DTC).>

There is a fault.

Repair or replace 
ATF temperature 
sensor circuit.

Go to step 9.

9

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.

Go to step 10.

10

CHECK MECHANICAL TROUBLE.
Check mechanical trouble in automatic trans-
mission.
Is there any mechanical trouble in automatic 
transmission?

There is mechanical trouble.

Repair or replace 
automatic trans-
mission. <Ref. to 
AT-32, INSPEC-
TION, Road Test.>

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

Step

Value

Yes

No

EN(H4SO)-254

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

BL:DTC P0851 — NEUTRAL SWITCH INPUT CIRCUIT LOW (AT MODEL) —

• DTC DETECTING CONDITION:

• Two consecutive driving cycles with fault

• TROUBLE SYMPTOM:

• Erroneous idling

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-00740

12

INHIBITOR SWITCH

7

P

R

N

D

3

2

1

12

11

T7

T3

B12

B14

B12

T7

1 2 3 4 5 6
7 8 9 10 11 12

21

B136

ECM

STARTER MOTOR

1 2 3 4
5 6 7 8
9 10 11 12

B136

5 6

7

2

1

9

8

4

3

23

21 22

24

10 11 12 13 14

25 26

15 16 17

18 19 20

EN(H4SO)-255

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK ANY OTHER DTC ON DISPLAY.
Is any other DTC displayed?

DTC indicated.

Inspect the rele-
vant DTC using 
“List of Diagnos-
tics Trouble Code 
(DTC)”. <Ref. to 
EN(H4SO)-83, List 
of Diagnostic 
Trouble Code 
(DTC).>

Go to step 2.

2

CHECK INPUT SIGNAL FOR ECM.
1) Turn ignition switch to ON.
2) Measure voltage between ECM and chas-

sis ground.

Connector & terminal

(B136) No. 21 (+) — Chassis ground (

−−−−

):

Is the measured value within the specified 
value at except “N” and “P” position?

4.5 V - 5.5 V

Even if MI lights 
up, the circuit has 
returned to a nor-
mal condition at 
this time.

Go to step 3.

3

CHECK HARNESS BETWEEN ECM AND 
TRANSMISSION HARNESS CONNECTOR.
1) Turn ignition switch to OFF.
2) Disconnect connectors from ECM and 

transmission harness connector (T3).

3) Measure resistance of harness between 

ECM connector and chassis ground.

Connector & terminal

(B136) No. 21 — Chassis ground:

Does the measured value exceed the spec-
ified value?

1 M

Ω

Go to step 4.

Repair ground 
short circuit in har-
ness between 
ECM and trans-
mission harness 
connector.

4

CHECK TRANSMISSION HARNESS CON-
NECTOR.
1) Disconnect connector from inhibitor switch.
2) Measure resistance of harness between 

transmission harness connector and 
engine ground.

Connector & terminal

(T3) No. 12 — Engine ground:

Does the measured value exceed the spec-
ified value?

1 M

Ω

Go to step 5.

Repair ground 
short circuit in har-
ness between 
transmission har-
ness and inhibitor 
switch connector.

5

CHECK INHIBITOR SWITCH.
Measure resistance between inhibitor switch 
connector receptacle's terminals in select lever 
except for “N” position.

Terminals

No. 7 — No. 12:

Does the measured value exceed the specified 
value at except "N" and "P" positions?

1 M

Ω

Go to step 6.

Replace inhibitor 
switch.  <Ref. to 
AT-49, Inhibitor 
Switch.>

6

CHECK SELECTOR CABLE CONNECTION.
Is there any fault in selector cable connection 
to inhibitor switch?

There is a fault.

Repair selector 
cable connection.  
<Ref. to CS-12, 
Select Cable.>

Contact SUBARU 
distributor service.

NOTE:
Inspection by DTM
is required, be-
cause probable
cause is deteriora-
tion of multiple
parts.