Subaru Legacy (2005 year). Manual - part 137

EN(H4SO 2.0)(diag)-137

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

22

GROUP OF #1 AND #2 CYLINDERS

Are there any faults in #1 and 
#2 cylinders?

Repair or replace 
faulty parts.

NOTE:
(1) Check the fol-
lowing items.

• Spark plug
• Fuel injector
• Ignition coil
• Compres-
sion ratio

(2) If no abnormal 
is discovered, 
check for “IGNI-
TION CONTROL 
SYSTEM” of #1 
and #2 cylinders 
side. <Ref. to 
EN(H4SO 
2.0)(diag)-56, 
IGNITION CON-
TROL SYSTEM, 
Diagnostics for 
Engine Starting 
Failure.>

Go to DTC P0171. 
<Ref. to EN(H4SO 
2.0)(diag)-123, 
DTC P0171 SYS-
TEM TOO LEAN 
(BANK 1), Diag-
nostic Procedure 
with Diagnostic 
Trouble Code 
(DTC).>

23

GROUP OF #3 AND #4 CYLINDERS

Are there any faults in #3 and 
#4 cylinders?

Repair or replace 
faulty parts.

NOTE:
(1) Check the fol-
lowing items.

• Spark plug
• Fuel injector
• Ignition coil

(2) If no abnormal 
is discovered, 
check for “16. D: 
IGNITION CON-
TROL SYSTEM” 
of #3 and #4 cylin-
ders side. <Ref. to 
EN(H4SO 
2.0)(diag)-56, 
IGNITION CON-
TROL SYSTEM, 
Diagnostics for 
Engine Starting 
Failure.>

Go to DTC P0171. 
<Ref. to EN(H4SO 
2.0)(diag)-123, 
DTC P0171 SYS-
TEM TOO LEAN 
(BANK 1), Diag-
nostic Procedure 
with Diagnostic 
Trouble Code 
(DTC).>

24

GROUP OF #1 AND #3 CYLINDERS

Are there any faults in #1 and 
#3 cylinders?

Repair or replace 
faulty parts.

NOTE:
Check the follow-
ing items.
• Spark plug
• Fuel injector
• Skipping timing 
belt teeth

Go to DTC P0171. 
<Ref. to EN(H4SO 
2.0)(diag)-123, 
DTC P0171 SYS-
TEM TOO LEAN 
(BANK 1), Diag-
nostic Procedure 
with Diagnostic 
Trouble Code 
(DTC).>

Step

Check

Yes

No

EN(H4SO 2.0)(diag)-138

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

25

GROUP OF #2 AND #4 CYLINDERS

Are there any faults in #2 and 
#4 cylinders?

Repair or replace 
faulty parts.

NOTE:
Check the follow-
ing items.
• Spark plug
• Fuel injector
• Compression 
ratio
• Skipping timing 
belt teeth

Go to DTC P0171. 
<Ref. to EN(H4SO 
2.0)(diag)-123, 
DTC P0171 SYS-
TEM TOO LEAN 
(BANK 1), Diag-
nostic Procedure 
with Diagnostic 
Trouble Code 
(DTC).>

26

CYLINDER AT RANDOM

Is the engine idle rough?

Go to DTC P0171. 
<Ref. to EN(H4SO 
2.0)(diag)-123, 
DTC P0171 SYS-
TEM TOO LEAN 
(BANK 1), Diag-
nostic Procedure 
with Diagnostic 
Trouble Code 
(DTC).>

Repair or replace 
faulty parts.

NOTE:
Check the follow-
ing items.
• Spark plug
• Fuel injector
• Compression 
ratio

Step

Check

Yes

No

EN(H4SO 2.0)(diag)-139

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AE:DTC P0327 KNOCK SENSOR 1 CIRCUIT LOW (BANK 1 OR SINGLE SEN-

SOR)

DTC DETECTING CONDITION:
Immediately at fault recognition
TROUBLE SYMPTOM:
• Poor driving performance
• Knocking occurs.

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:

EN-03480

23

12

KNOCK

SENSOR

13

2

ECM

B136

B20

E1

E14

E14

B20

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

1 2

1 2 3 4
5 6 7 8
9 10 11 12

14

13

15 16

EN(H4SO 2.0)(diag)-140

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK HARNESS BETWEEN KNOCK SEN-
SOR AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM har-
ness connector and chassis ground.

Connector & terminal

(B136) No. 23 — Chassis ground:

Is the resistance more than 
700 k

Ω?

Go to step 2.

Repair the har-
ness and connec-
tor.

NOTE:
In this case, repair
the following item:
• Open circuit of 
harness between 
knock sensor and 
ECM connector
• Poor contact in 
knock sensor con-
nector
• Poor contact in 
coupling connector

2

CHECK KNOCK SENSOR.
1) Disconnect the connector from knock sen-
sor.
2) Measure the resistance between knock 
sensor connector terminal and engine ground.

Terminals

No. 2 — Engine ground:

Is the resistance more than 
700 k

Ω?

Go to step 3.

Repair the har-
ness and connec-
tor.

NOTE:
In this case, repair
the following item:
• Poor contact in 
knock sensor con-
nector

3

CHECK INSTALLATION CONDITION OF 
KNOCK SENSOR.

Is the knock sensor installation 
bolt tightened securely?

Replace the knock 
sensor. <Ref. to 
FU(H4SO 2.0)-23, 
Knock Sensor.>

Tighten the knock 
sensor installation 
bolt securely.