Subaru Legacy (2005 year). Service manual - part 214

EN(H4SO 2.5)(diag)-141

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 SENSOR OUTPUT.
1) Turn the ignition switch to ON.
2) Read the data of sub throttle sensor signal 
using Subaru Select Monitor.

NOTE:

For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4SO 2.5)(diag)-25, Subaru Select Mon-
itor.>

Is the voltage less than 4.73 
V?

Go to step 3.

Go to step 4.

3

CHECK POOR CONTACT.
Check poor contact in connector between 
ECM and electronic throttle control.

Is there poor contact in con-
nector between ECM and elec-
tronic throttle control?

Repair the poor 
contact.

Temporary poor 
contact occurred, 
but it is normal at 
present.

4

CHECK HARNESS BETWEEN ECM AND 
ELECTRONIC THROTTLE CONTROL.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Disconnect the connectors from electronic 
throttle control.
4) Measure the resistance between ECM con-
nector and electronic throttle control connector.

Connector & terminal

(B136) No. 35 — (E57) No. 3:
(B136) No. 29 — (E57) No. 4:

Is the resistance less than 1 
Ω?

Go to step 5.

Repair the open 
circuit of harness 
connector.

5

CHECK HARNESS BETWEEN ECM AND 
ELECTRONIC THROTTLE CONTROL.
1) Connect the ECM connector.
2) Measure the resistance between electronic 
throttle control connector and engine ground.

Connector & terminal

(E57) No. 3 — Engine ground:

Is the resistance less than 5 
Ω?

Go to step 6.

Repair the poor 
contact in ECM 
connector. 
Replace the ECM 
if defective. <Ref. 
to FU(H4SO 2.5)-
37, Engine Con-
trol Module 
(ECM).>

6

CHECK HARNESS BETWEEN ECM AND 
ELECTRONIC THROTTLE CONTROL.
Measure the voltage between electronic throt-
tle control connector and engine ground.

Connector & terminal

(E57) No. 4 (+) — Engine ground (

−

):

Is the voltage less than 10 V?

Go to step 7.

Repair the battery 
short circuit of har-
ness between 
ECM connector 
and electronic 
throttle control 
connector.

7

CHECK HARNESS BETWEEN ECM AND 
ELECTRONIC THROTTLE CONTROL.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between connector 
terminals.

Connector & terminal

(B136) No. 29 — (B136) No. 16:

Is the resistance more than 1 
M

Ω?

Repair the poor 
contact. Replace 
the electronic 
throttle control.

Sensor power sup-
ply circuit may be 
shorted.

EN(H4SO 2.5)(diag)-142

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AB:DTC P0301 CYLINDER 1 MISFIRE DETECTED

NOTE:
For the diagnostic procedure, refer to DTC P0304. <Ref. to EN(H4SO 2.5)(diag)-143, DTC P0304 CYLIN-
DER 4 MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

AC:DTC P0302 CYLINDER 2 MISFIRE DETECTED

NOTE:
For the diagnostic procedure, refer to DTC P0304. <Ref. to EN(H4SO 2.5)(diag)-143, DTC P0304 CYLIN-
DER 4 MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

AD:DTC P0303 CYLINDER 3 MISFIRE DETECTED

NOTE:
For the diagnostic procedure, refer to DTC P0304. <Ref. to EN(H4SO 2.5)(diag)-143, DTC P0304 CYLIN-
DER 4 MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

EN(H4SO 2.5)(diag)-143

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AE:DTC P0304 CYLINDER 4 MISFIRE DETECTED

DTC DETECTING CONDITION:
• Detects when malfunction occurs in 2 continuous driving cycles.
• Immediately at fault recognition (A misfire which could damage catalyst occurs.)
TROUBLE SYMPTOM:
• Engine stalls.
• Erroneous idling
• Rough driving

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-03456

E6

E17

E5

E16

1 2

1

2

1

2

1

2

1

2

4

5

6

3

42

48

43

44

45

ECM

B136

E5

E16

E6

E17

B21

E2

FUEL INJECTOR

No. 1

FUEL INJECTOR

No. 2

FUEL INJECTOR

No. 3

FUEL INJECTOR

No. 4

BATTERY

SBF-7

B47

MAIN RELAY

1

2

6

3

5

B47

3

4

1

2

5

6

E

B136

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

33 34

29

32

30

31

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

4

EN(H4SO 2.5)(diag)-144

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?

Inspect the rele-
vant 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 OUTPUT SIGNAL FROM ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM con-
nector and chassis ground on faulty cylinders.

Connector & terminal

#1 (B136) No. 6 (+) — Chassis ground (

−

):

#2 (B136) No. 5 (+) — Chassis ground (

−

):

#3 (B136) No. 4 (+) — Chassis ground (

−

):

#4 (B136) No. 3 (+) — Chassis ground (

−

):

Is the voltage more than 10 V? Go to step 8.

Go to step 4.

4

CHECK HARNESS BETWEEN FUEL INJEC-
TOR AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel injector 
on faulty cylinders.
3) Disconnect the connector from ECM.
4) Measure the resistance between ECM con-
nector and engine ground on faulty cylinders.

Connector & terminal

#1 (E5) No. 1 — Engine ground:
#2 (E16) No. 1 — Engine ground:
#3 (E6) No. 1 — Engine ground:
#4 (E17) No. 1 — Engine ground:

Is the resistance more than 1 
M

Ω?

Go to step 5.

Repair the ground 
short circuit of har-
ness between fuel 
injector and ECM 
connector.

5

CHECK HARNESS BETWEEN FUEL INJEC-
TOR AND ECM CONNECTOR.
Measure the resistance of harness connector 
between ECM connector and fuel injector on 
faulty cylinders.

Connector & terminal

#1 (B136) No. 6 — (E5) No. 1:
#2 (B136) No. 5 — (E16) No. 1:
#3 (B136) No. 4 — (E6) No. 1:
#4 (B136) No. 3 — (E17) No. 1:

Is the resistance less than 1 
Ω?

Go to step 6.

Repair the har-
ness and connec-
tor.

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

6

CHECK FUEL INJECTOR.
Measure the resistance between fuel injector 
terminals on faulty cylinder.

Terminals

No. 1 — No. 2:

Is the resistance 5 — 20 

Ω?

Go to step 7.

Replace the faulty 
fuel injector. <Ref. 
to FU(H4SO 2.5)-
32, Fuel Injector.>