Subaru Legacy (2005 year). Manual - part 225

EN(H4SO 2.5)(diag)-185

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

8

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

Connector & terminal

(B137) No. 9 — (B25) No. 2:

Is the resistance less than 1 
Ω?

Go to step 9.

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

9

CHECK HARNESS BETWEEN ECM AND 
NEUTRAL POSITION SWITCH CONNEC-
TOR.
Measure the resistance of harness between 
ECM and transmission harness connector.

Connector & terminal

(B25) No. 1 — Engine ground:

Is the resistance less than 5 
Ω?

Go to step 10.

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

10

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 
2.5)-37, Engine 
Control Module 
(ECM).>

Step

Check

Yes

No

EN(H4SO 2.5)(diag)-186

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

BB:DTC P0852 PARK/NEUTRAL POSITION 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, conduct Clear Memory Mode <Ref. to EN(H4SO 2.5)(diag)-
40, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4SO 2.5)(diag)-33, Inspection Mode.>.
WIRING DIAGRAM:
• EC, EK, EH, ER and K4 model

• KA and KS model

NOTE:
Fuel injection system for KA and KS model is the same as 2.0 L model. Refer to EN(H4SO 2.0) section.

EN-03515

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

B137

5

6

7

8

2

1

9

4

3

10

22 23

11 12 13 14 15

24 25

26

16 17

18 19 20 21

27

28 29

30 31

B25

1 2

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

1 2 3 4
5 6 7 8

B122

B138

B12

T3

T7

P

R

N

D

3

2

1

12

7

12

11

B137

9

E

E

1

B25

T2

T2

B25

2

AT

MT

E2

B21

B138

*

*

36

B122

LHD :

RHD :

INHIBITOR SWITCH

ECM

NEUTRAL
POSITION
SWITCH

*

: TERMINAL No. RANDOM ARRANGEMENT

EN(H4SO 2.5)(diag)-187

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK OPTION CODE.

Is the option code EC, EK, EH, 
ER or K4?

Go to step 2.

Refer to EN(H4SO 
2.0) section. <Ref. 
to EN(H4SO 
2.0)(diag)-64, List 
of Diagnostic Trou-
ble Code (DTC).>

NOTE:
Fuel injection sys-
tem for KA and KS
model is the same
as 2.0 L model.

2

CHECK ANY OTHER DTC ON DISPLAY.

Is any other DTC displayed?

Check DTC using 
“List of Diagnostic 
Trouble Code 
(DTC)”. <Ref. to 
EN(H4SO 
2.5)(diag)-69, List 
of Diagnostic Trou-
ble Code (DTC).>

Go to step 3.

3

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

(B137) No. 9 (+) — Chassis ground (

−

):

Is the voltage less than 1 V?

Go to step 4.

Go to step 6.

4

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

(B137) No. 9 (+) — Chassis ground (

−

):

Is the voltage more than 10 V? Go to step 5.

Go to step 6.

5

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 
2.5)-37, Engine 
Control Module 
(ECM).>

6

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

Connector & terminal

(B137) No. 9 (+) — 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 7.

7

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

(B137) No. 9 — (T7) No. 12:

Is the resistance less than 1 
Ω?

Go to step 8.

Repair the har-
ness and connec-
tor.

NOTE:
In this case, repair
the following:
• 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 2.5)(diag)-188

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

8

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

Connector & terminal

(T7) No. 7 — Engine ground:

Is the resistance less than 5 
Ω?

Go to step 9.

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

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

9

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 10.

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

10

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 
2.5)-37, Engine 
Control Module 
(ECM).>

Step

Check

Yes

No