Subaru Legacy III (2000-2003 year). Service manual — part 502

EN(H4DOSTC)-178

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

AP:DTC P0852 — NEUTRAL SWITCH INPUT CIRCUIT HIGH (MT 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(H4DOSTC)-35,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOSTC)-33, OPERATION,
Inspection Mode.> .
• WIRING DIAGRAM:

EN-01004

2

1

8

B134

ECM

NEUTRAL
POSITION
SWITCH

B128

T9

T9

B128

B22

E3

16

B128

B22

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

B134

3 4

1 2

1 2 3 4

10 11 12

19 20 21

13

5

6

14 15

7

8 9

16 17

18

22

EN(H4DOSTC)-179

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

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

sis ground.

Connector & terminal

(B134) No. 8 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value in neutral position?

5 V

Go to step 2.

Go to step 4.

2

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

Connector & terminal

(B134) No. 8 (+) — Chassis ground (

−−−−

):

Is the measured value less than the specified
value at except neutral position?

1 V

Go to step 3.

Go to step 5.

3

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.

Contact SUBARU
distributor service.

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

4

CHECK NEUTRAL POSITION SWITCH.
Measure resistance between transmission har-
ness connector terminals.

Connector & terminal

(T9) No. 1 — No. 2:

Is the measured value less than the specified
value at except neutral position?

1

Ω

Go to step 5.

Repair open circuit
in transmission
harness or replace
neutral position
switch.

5

CHECK HARNESS BETWEEN ECM AND
NEUTRAL POSITION SWITCH CONNEC-
TOR.
1) Disconnect connector from ECM.
2) Measure resistance of harness between

ECM and transmission harness connector.

Connector & terminal

(B134) No. 8 — (B128) No. 1:

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

1

Ω

Go to step 6.

Repair open circuit
in harness
between ECM and
transmission har-
ness connector.

6

CHECK HARNESS BETWEEN ECM AND
NEUTRAL POSITION SWITCH CONNEC-
TOR.
Measure resistance of harness between trans-
mission harness connector and engine ground.

Connector & terminal

(B128) No. 2 — Engine ground:

Is the measured value less than the specified
value?

5

Ω

Go to step 7.

Repair harness
and connector.

NOTE:
In this case, repair
the following:
• Open circuit in
harness between
transmission har-
ness connector
and engine
grounding terminal
• Poor contact in
coupling connector

EN(H4DOSTC)-180

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

7

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

There is poor contact.

Repair poor con-
tact in transmis-
sion harness
connector.

Contact SUBARU
distributor service.

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

Step

Value

Yes

No

EN(H4DOSTC)-181

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

AQ:DTC P1110 — ATMOSPHERIC PRESSURE SENSOR CIRCUIT MALFUNC-

TION (LOW INPUT) —

CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H4DOSTC)-35,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOSTC)-33, Inspection
Mode.> .

Step

Value

Yes

No

1

CHECK ANY OTHER DTC ON DISPLAY.
Does the Subaru Select Monitor indicate DTC
P1110?

DTC P1110 indicated.

Replace the ECM.
<Ref. to
FU(H4DOSTC)-
40, Engine Con-
trol Module.>

NOTE:
Atmospheric pres-
sure sensor is built
into ECM.

It is not necessary
to inspect DTC
P1110.