Subaru Legacy (2005 year). Manual - part 145

EN(H4SO 2.0)(diag)-169

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

9

CHECK POOR CONTACT.
Check poor contact in transmission harness 
connector.

Is there poor contact in trans-
mission harness connector?

Repair the poor 
contact in trans-
mission harness 
connector.

Replace the ECM. 
<Ref. to FU(H4SO 
2.0)-34, Engine 
Control Module 
(ECM).>

Step

Check

Yes

No

EN(H4SO 2.0)(diag)-170

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

BA:DTC P0852 PARK/NEUTRAL SWITCH INPUT CIRCUIT HIGH

1. AT MODEL

DTC DETECTING CONDITION:
Detects when malfunction occurs in 2 continuous driving cycles.
TROUBLE SYMPTOM:
Erroneous idling

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4SO 2.0)(diag)-
38, OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4SO 2.0)(diag)-32, PRO-
CEDURE, Inspection Mode.>.
WIRING DIAGRAM:

B12

T3

B14

T7

INHIBITOR SWITCH

NEUTRAL
POSITION
SWITCH

STARTER MOTOR

P

R

N

D

3

2

1

7

12

11

12

B135

ECM

12

B12

T7

1 2 3 4 5 6
7 8 9 10 11 12

1 2 3 4
5 6 7 8
9 10 11 12

E

1

B25

T2

T2

B25

2

MT

AT

EN-03485

M

36

B135

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

29 30 31

32 33

34 35

B21

1 2 3 4

12 13 14 15

5 6 7 8

16 17 18 19

9 10 11

20 21 22

23 24 25 26 27 28 29 30 31 32 33

35

34

37

36

39

38

41

40

43

42

44

45

47

46

49

48

51

50

53

52

54

B25

1 2

1 2 3 4
5 6 7 8

B83    : RHD

B122   : LHD

*

: TERMINAL No. RANDOM ARRANGEMENT

B83

B122 : LHD

: RHD

 E2

B21

*

*

EN(H4SO 2.0)(diag)-171

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK ANY OTHER DTC ON DISPLAY.

Is any other DTC displayed?

Check DTC using 
“List of Diagnostic 
Trouble Code 
(DTC)”. <Ref. to 
EN(H4SO 
2.0)(diag)-64, List 
of Diagnostic Trou-
ble Code (DTC).>

Go to step 2.

2

CHECK INPUT SIGNAL OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM and 
chassis ground with select lever at “N” and “P” 
range.

Connector & terminal

(B135) No. 12 (+) — Chassis ground (

−

):

Is the voltage less than 1 V?

Go to step 3.

Go to step 5.

3

CHECK INPUT SIGNAL OF ECM.
Measure the voltage between ECM and chas-
sis ground with select lever at other than “N” 
and “P” range.

Connector & terminal

(B135) No. 12 (+) — Chassis ground (

−

):

Is the voltage more than 10 V? Go to step 4.

Go to step 5.

4

CHECK POOR CONTACT.
Check poor contact in ECM connector.

Is there poor contact in ECM 
connector?

Repair the poor 
contact in ECM 
connector.

Replace the ECM. 
<Ref. to FU(H4SO 
2.0)-34, Engine 
Control Module 
(ECM).>

5

CHECK INPUT SIGNAL OF ECM.
Measure the voltage between ECM and chas-
sis ground.

Connector & terminal

(B135) No. 12 (+) — Chassis ground (

−

):

Is the voltage more than 10 V? Repair the battery 

short circuit of har-
ness between 
ECM and inhibitor 
switch connector.

Go to step 6.

6

CHECK HARNESS BETWEEN ECM AND IN-
HIBITOR SWITCH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and 
inhibitor switch.
3) Measure the resistance of harness 
between ECM and inhibitor switch connector.

Connector & terminal

(B135) No. 12 — (T7) No. 7:

Is the resistance less than 1 
Ω?

Go to step 7.

Repair the har-
ness and connec-
tor.

NOTE:
In this case, repair
the following item:
• Open circuit of 
harness between 
ECM and inhibitor 
switch connector
• Poor contact in 
coupling connector
• Poor contact in 
inhibitor switch 
connector
• Poor contact in 
ECM connector

EN(H4SO 2.0)(diag)-172

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

7

CHECK INHIBITOR SWITCH GROUND LINE.
Measure the resistance of harness between 
inhibitor switch connector and engine ground.

Connector & terminal

(T7) No. 12 — Engine ground:

Is the resistance less than 5 
Ω?

Go to step 8.

Repair the open 
circuit of harness 
between inhibitor 
switch connector 
and ground line.

NOTE:
In this case, repair
the following item:
• Open circuit of 
harness between 
inhibitor switch 
connector and 
ground line

8

CHECK INHIBITOR SWITCH.
Measure the resistance between inhibitor 
switch connector receptacle’s terminals with 
select lever at “N” and “P” range.

Terminals

(T7) No. 7 — No. 12:

Is the resistance less than 1 
Ω?

Go to step 9.

Replace the inhibi-
tor switch. <Ref. to 
4AT-51, Inhibitor 
Switch.>

9

CHECK SELECT CABLE CONNECTION.

Is there any fault in select 
cable connection to inhibitor 
switch?

Repair the select 
cable connection. 
<Ref. to CS-29, 
INSPECTION, 
Select Cable.>

Replace the ECM. 
<Ref. to FU(H4SO 
2.0)-34, Engine 
Control Module 
(ECM).>

Step

Check

Yes

No