Subaru Legacy III (2000-2003 year). Manual — part 375

EN(H6DO)-302

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

CE:DTC P0865 — TCM COMMUNICATION CIRCUIT LOW —

• DTC DETECTING CONDITION:

• Two consecutive driving cycles with fault

CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H6DO)-54, OP-
ERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)-47, OPERATION, Inspec-
tion Mode.>.
• WIRING DIAGRAM:

EN-01099

B56

B135

20

21

B135 ECM

TCM

B56

1 2

7

8

9

5 6

3 4

10 11 12
19 20 21

13

14 15

16

17

18

22

23

24

5 6

7 8

2

1

9

4

3

10

24

22

23

25

11 12 13 14 15

26 27 28

16 17 18 19

20 21

EN(H6DO)-303

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK HARNESS BETWEEN ECM AND
TCM CONNECTOR.
1) Turn ignition switch to ON.
2) Measure voltage between ECM and chas-

sis ground.

Connector & terminal

(B135) No. 20 (+) — Chassis ground (

−−−−

):

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

1 V

Go to step 2.

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

NOTE:
In this case, repair
the following:
• Poor contact in
ECM connector
• Poor contact in
TCM connector

2

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

ECM and chassis ground.

Connector & terminal

(B135) No. 20 — Chassis ground:

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

10

Ω

Repair ground
short circuit in har-
ness between
ECM and TCM
connector.

Go to step 3.

3

CHECK OUTPUT SIGNAL FOR ECM.
1) Connect connector to ECM.
2) Turn ignition switch to ON.
3) Measure voltage between ECM and chas-

sis ground.

Connector & terminal

(B135) No. 20 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

5 V

Go to step 4.

Repair poor con-
tact in ECM con-
nector.

4

CHECK TROUBLE CODE FOR AUTOMATIC
TRANSMISSION.
Read trouble code for automatic transmission.
<Ref. to AT-24, Read Diagnostic Trouble Code
(DTC).>
Does trouble code appear for automatic trans-
mission?

Trouble code for automatic
transmission is indicated.

Inspect trouble
code for auto-
matic transmis-
sion.

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

EN(H6DO)-304

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

CF:DTC P0866 — TCM COMMUNICATION CIRCUIT HIGH —

• DTC DETECTING CONDITION:

• Two consecutive driving cycles with fault

CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H6DO)-54, OP-
ERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)-47, OPERATION, Inspec-
tion Mode.>.
• WIRING DIAGRAM:

EN-01099

B56

B135

20

21

B135 ECM

TCM

B56

1 2

7

8

9

5 6

3 4

10 11 12
19 20 21

13

14 15

16

17

18

22

23

24

5 6

7 8

2

1

9

4

3

10

24

22

23

25

11 12 13 14 15

26 27 28

16 17 18 19

20 21

EN(H6DO)-305

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK HARNESS BETWEEN ECM AND
TCM CONNECTOR.
1) Turn ignition switch to ON.
2) Measure voltage between ECM and chas-

sis ground.

Connector & terminal

(B135) No. 20 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Repair battery
short circuit in har-
ness between
ECM and TCM
connector.

Go to step 2.

2

CHECK HARNESS BETWEEN ECM AND
TCM CONNECTOR.
Measure voltage between ECM connector and
chassis ground.

Connector & terminal

(B135) No. 20 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the specified
value?

4 V

Go to step 5.

Go to step 3.

3

CHECK HARNESS BETWEEN ECM AND
TCM CONNECTOR.
Measure voltage between ECM connector and
chassis ground.

Connector & terminal

(B135) No. 20 (+) — Chassis ground (

−−−−

):

Is the measured value less than the specified
value?

1 V

Repair poor con-
tact in ECM con-
nector.

Go to step 4.

4

CHECK OUTPUT SIGNAL FROM ECM.
Measure voltage between ECM and chassis
ground.

Connector & terminal

(B135) No. 20 (+) — Chassis ground (

−−−−

):

Does the measured value change within the
specified range?

1 V — 4 V

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

NOTE:
In this case, repair
the following:
• Poor contact in
ECM connector
• Poor contact in
TCM connector

Contact SUBARU
distributor service.

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

5

CHECK HARNESS BETWEEN ECM AND
TCM CONNECTOR.
Measure voltage between TCM and chassis
ground.

Connector & terminal

(B56) No. 21 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the specified
value?

4 V

Go to step 6.

Repair open circuit
in harness
between ECM and
TCM connector.

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.

Check TCM power
supply line and
grounding line.