Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 270

EN(H4DOTC)(diag)-304

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK OUTPUT SIGNAL OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground.

Connector & terminal

(B135) No. 3 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step

2.

Go to step

3.

2

CHECK FOR POOR CONTACT.
Check for poor contact of ECM connector.

Is there poor contact of ECM
connector?

Repair the poor
contact of ECM
connector.

Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:

In this case, tem-
porary open or
short circuit of har-
ness or temporary
poor contact of
connector may be
the cause.

3

CHECK POWER SUPPLY TO PRESSURE
CONTROL SOLENOID VALVE ASSEMBLY.
Measure the voltage between the pressure con-
trol solenoid valve assembly and chassis
ground.

Connector & terminal

(R68) No. 1 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step

4.

Repair the power
supply circuit.

4

CHECK HARNESS BETWEEN ECM AND
PRESSURE CONTROL SOLENOID VALVE
ASSEMBLY CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the ECM
and pressure control solenoid valve assembly.
3) Measure the resistance between the pres-
sure control solenoid valve assembly connector
and chassis ground.

Connector & terminal

(R68) No. 2 — Chassis ground:

Is the resistance 1 MΩ or
more?

Go to step

5.

Repair the short
circuit to ground in
harness between
ECM connector
and pressure con-
trol solenoid valve
assembly connec-
tor.

5

CHECK HARNESS BETWEEN ECM AND
PRESSURE CONTROL SOLENOID VALVE
ASSEMBLY CONNECTOR.
Measure the resistance of harness between
ECM connector and pressure control solenoid
valve assembly connector.

Connector & terminal

(B135) No. 3 — (R68) No. 2:

Is the resistance less than 1 Ω? Go to step

6.

Repair the harness
and connector.
NOTE:

In this case, repair
the following item:
• Open circuit in
harness between
ECM

connector

and pressure con-
trol solenoid valve
assembly connec-
tor
• Poor contact of
coupling connector

EN(H4DOTC)(diag)-305

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

6

CHECK PRESSURE CONTROL SOLENOID
VALVE ASSEMBLY.
Measure the resistance between terminals of
pressure control solenoid valve assembly.

Terminals

No. 1 — No. 2:

Is the resistance 10 — 100 Ω? Repair the pres-

sure control sole-
noid valve
assembly connec-
tor for poor con-
tact.

Replace the pres-
sure control sole-
noid valve
assembly. <Ref. to
EC(STI)-16, Pres-
sure Control Sole-
noid Valve
Assembly.> <Ref.
to EC(w/o STI)-17,
Pressure Control
Solenoid Valve
Assembly.>

Step

Check

Yes

No

EN(H4DOTC)(diag)-306

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

DM:DTC P1410 SECONDARY AIR INJECTION SYSTEM SWITCHING VALVE

STUCK OPEN

DTC DETECTING CONDITION:

• Immediately at fault recognition

• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-209, DTC P1410 SECONDARY AIR INJECTION SYS-

TEM SWITCHING VALVE STUCK OPEN, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:

After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-63,

OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-49, PROCE-

DURE, Inspection Mode.>.

Step

Check

Yes

No

1

CHECK SECONDARY AIR COMBINATION
VALVE.
1) Remove the secondary air combination
valve. <Ref. to EC(STI)-29, Secondary Air
Combination Valve.> <Ref. to EC(w/o STI)-30,
Secondary Air Combination Valve.>
2) Blow in air from the secondary air combina-
tion valve air inlet, and check whether there are
leaks at the pipe connections.

Are there air leaks from the pipe
connections?

Replace the sec-
ondary air combi-
nation valve on the
side with the air
leak. <Ref. to
EC(STI)-29, Sec-
ondary Air Combi-
nation Valve.>
<Ref. to EC(w/o
STI)-30, Second-
ary Air Combina-
tion Valve.>

Perform the diag-
nostic procedure of
DTC P2440. <Ref.
to
EN(H4DOTC)(diag)
-446, DTC P2440
SECONDARY AIR
INJECTION SYS-
TEM SWITCHING
VALVE STUCK
OPEN (BANK1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>

EN(H4DOTC)(diag)-307

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

DN:DTC P1420 FUEL TANK PRESSURE CONTROL SOL. VALVE CIRCUIT HIGH

DTC DETECTING CONDITION:

• Detected when 2 consecutive driving cycles with fault occur.

• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-211, DTC P1420 FUEL TANK PRESSURE CONTROL

SOL. VALVE CIRCUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:

After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-63,

OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-49, PROCE-

DURE, Inspection Mode.>.

WIRING DIAGRAM:

• Engine electrical system, without SI-DRIVE <Ref. to WI-32, WITHOUT SI-DRIVE, WIRING DIAGRAM,

Engine Electrical System.>

• Engine electrical system, with SI-DRIVE <Ref. to WI-48, WITH SI-DRIVE, WIRING DIAGRAM, Engine

Electrical System.>

ECM

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

B135

B:

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

B137

D:

B21

1 2 3 4 5 6 7 8 9 10 11

12 13 14 15 16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33

34 35
42 43

36 37 38 39

48 49 50 51 52 53 54

40 41

44 45

46 47

E52

E4

1 2

B3

D15

D6

E2

B21

44

11

4

8

E4

2

1

E52

2

1

R68

2

1

B135

B:

R57

R15

10

11

R1

B97

R2

B98

7

10

R68

1 2

B220

13
14

15 16

17

27

24

25
26

20

21
22

23

29
30

31

28

32 35

33
34

37
38

39

36

40

8

9

10

11 12

1

2

5

3

4

7

6

19

18

R57

B97

1 2

3 4 5

6 7 8 9 10 11 12

EN-09251

B98

2 3 4 5

6 7 8 9

11 12 13 14

17 18 19 20

1

10

15 16

B220

24

23

22

21

B220

4

3

B137

D:

SBF-7

E

FUSE

(RELAY BLOCK)

MAIN RELAY

BATTERY

PRESSURE CONTROL

SOLENOID VALVE ASSY

PURGE CONTROL

SOLENOID VALVE 2

PURGE CONTROL

SOLENOID VALVE 1