Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual - part 308

EN(H4DOTC)(diag)-456

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

CHECK HARNESS BETWEEN FUSE BOX
AND SECONDARY AIR COMBINATION
VALVE LH CONNECTOR.
1) Remove the secondary air combination
valve fuse (10 A) from the fuse box.
2) Disconnect the connector from the second-
ary air combination valve LH.
3) Measure the resistance between the sec-
ondary air combination valve fuse and second-
ary air combination valve LH connector, and
chassis ground.

Connector & terminal

Models without SI-DRIVE

(F9) No. 5 — Chassis ground:
(E40) No. 2 — Chassis ground:

Models with SI-DRIVE

(F9) No. 5 — Chassis ground:
(E40) No. 6 — Chassis ground:

Is the resistance 1 MΩ or
more?

Replace the fuse
with a new part,
and connect the
secondary air com-
bination valve LH
connector.
Go to step

Repair the ground
short circuit of har-
ness between the
fuse box and the
secondary air com-
bination valve LH
connector.

CHECK SECONDARY AIR COMBINATION
VALVE LH OPERATION.
1) Connect the delivery (test) mode connector.
2) Turn the ignition switch to ON.
3) Perform operation check for the secondary
air combination valve LH using the Subaru
Select Monitor.
NOTE:

Refer to “Compulsory Valve Operation Check
Mode” for more operation procedures. <Ref. to
EN(H4DOTC)(diag)-64, Compulsory Valve Op-
eration Check Mode.>

Does the secondary air combi-
nation valve LH repeatedly
switch to ON and OFF?

Go to step

CHECK DUCT BETWEEN SECONDARY AIR
PUMP AND SECONDARY AIR COMBINA-
TION VALVE LH.
Check the duct between the secondary air
pump and secondary air combination valve LH.

Is there damage, clog or dis-
connection of the duct?

Replace, clean or
connect the duct.

Go to step

CHECK PIPE BETWEEN SECONDARY AIR
COMBINATION VALVE LH AND CYLINDER
HEAD.
Check the pipe between the secondary air com-
bination valve LH and cylinder head.

Is there damage, clog or dis-
connection of the pipe?

Replace, clean or
connect the pipe.

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  poor  con-
tact  of  connector,
temporary open or
short circuit of har-
ness  may  be  the
cause.

Step

Check

Yes

EN(H4DOTC)(diag)-457

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

CHECK POWER SUPPLY TO SECONDARY
AIR COMBINATION VALVE LH.
1) Disconnect the connector from the second-
ary air combination valve LH.
2) In the condition of step 3, measure the volt-
age between secondary air combination valve
LH connector and chassis ground.

Connector & terminal

Models without SI-DRIVE

(E40) No. 2 (+) — Chassis ground (–):

Models with SI-DRIVE

(E40) No. 6 (+) — Chassis ground (–):

Does the voltage repeatedly
change between 10 V and 0 V?

Replace the sec-
ondary air combi-
nation valve LH.
<Ref. to EC(STI)-
29, Secondary Air
Combination
Valve.> <Ref. to
EC(w/o STI)-30,
Secondary Air
Combination
Valve.>

Go to step

CHECK HARNESS BETWEEN SECONDARY
AIR COMBINATION VALVE LH AND CHAS-
SIS GROUND.
Measure the resistance between the secondary
air combination valve LH connector and chassis
ground.

Connector & terminal

Models without SI-DRIVE

(E40) No. 1 — Chassis ground:

Models with SI-DRIVE

(E40) No. 4 — Chassis ground:

Is the resistance less than 5 Ω? • Models without

SI-DRIVE: Go to
step

• Models with SI-
DRIVE: Go to step
14.

Repair the open
circuit in harness
between second-
ary air combination
valve LH connec-
tor and chassis
ground.

CHECK HARNESS BETWEEN SECONDARY
AIR COMBINATION VALVE RELAY 2 AND
SECONDARY AIR COMBINATION VALVE
LH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Remove the secondary air combination
valve relay 2 from the relay box.
3) Measure the resistance of the harness
between the secondary air combination valve
relay 2 and secondary air combination valve LH
connector.

Connector & terminal

(F9) No. 8 — (E40) No. 2:

Is the resistance less than 1 Ω? Go to step

Repair the harness
and connector.
NOTE:

In this case, repair
the following item:
• Open  circuit  in
harness  between
secondary air com-
bination  valve  re-
lay  2  connector
and  secondary  air
combination  valve
LH connector
• Poor  contact  of
coupling connector

CHECK SECONDARY AIR COMBINATION
VALVE RELAY 2.
1) Connect the battery to terminals No. 10 and
No. 9 of the secondary air combination valve
relay 2.
2) Measure the resistance between the sec-
ondary air combination valve relay 2 terminals.

Terminals

No. 7 — No. 8:

Is the resistance less than 1 Ω? Go to step

10.

Replace the sec-
ondary air combina-
tion valve relay 2.
<Ref. to
EN(H4DOTC)(diag)
-9, Electrical Com-
ponent Location.>

CHECK SECONDARY AIR COMBINATION
VALVE RELAY 2.
Measure the resistance between the secondary
air combination valve relay 2 terminals with the
battery disconnected.

Terminals

No. 7 — No. 8:

Is the resistance 1 MΩ or
more?

Go to step

11.

Replace the sec-
ondary air combina-
tion valve relay 2.
<Ref. to
EN(H4DOTC)(diag)
-9, Electrical Com-
ponent Location.>

Step

Check

Yes

EN(H4DOTC)(diag)-458

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

CHECK SECONDARY AIR COMBINATION
VALVE RELAY 2 POWER SUPPLY.
1) Turn the ignition switch to ON.
2) Measure the voltage between the second-
ary air combination valve relay 2 connector and
chassis ground.

Connector & terminal

(F9) No. 7 (+) — Chassis ground (–):
(F9) No. 10 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step

12.

Repair the open or
ground short circuit
of power supply
circuit.

CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 2 CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the ECM connector.
3) Measure the resistance of harness between
ECM connector and secondary air combination
valve relay 2 connector.

Connector & terminal

(B135) No. 20 — (F9) No. 9:

Is the resistance less than 1 Ω? Go to step

13.

Repair the harness
and connector.
NOTE:

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

connector

and  secondary  air
combination  valve
relay 2 connector
• Poor  contact  of
coupling connector

CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 2 CONNECTOR.
Measure the resistance between the secondary
air combination valve relay 2 connector and
chassis ground.

Connector & terminal

(F9) No. 9 — Chassis ground:

Is the resistance 1 MΩ or
more?

Repair the poor
contact of ECM
connector.

Repair the short
circuit to ground in
harness between
ECM connector
and secondary air
combination valve
relay 2 connector.

CHECK HARNESS BETWEEN SECONDARY
AIR COMBINATION VALVE RELAY 1 AND
SECONDARY AIR COMBINATION VALVE
LH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Remove the secondary air combination
valve relay 1 from the relay box.
3) Measure the resistance of the harness
between the secondary air combination valve
relay 1 and secondary air combination valve LH
connector.

Connector & terminal

(F9) No. 3 — (E40) No. 6:

Is the resistance less than 1 Ω? Go to step

15.

Repair the harness
and connector.
NOTE:

In this case, repair
the following item:
• Open  circuit  in
harness  between
secondary air com-
bination  valve  re-
lay  1  connector
and  secondary  air
combination  valve
LH connector
• Poor  contact  of
coupling connector

CHECK SECONDARY AIR COMBINATION
VALVE RELAY 1.
1) Connect the battery to terminals No. 1 and
No. 2 of the secondary air combination valve
relay 1.
2) Measure the resistance between the sec-
ondary air combination valve relay 1 terminals.

Terminals

No. 3 — No. 4:

Is the resistance less than 1 Ω? Go to step

16.

Replace the sec-
ondary air combina-
tion valve relay 1.
<Ref. to
EN(H4DOTC)(diag)
-9, Electrical Com-
ponent Location.>

Step

Check

Yes

EN(H4DOTC)(diag)-459

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

FN:DTC P2443 SECONDARY AIR INJECTION SYSTEM SWITCHING VALVE

STUCK CLOSED (BANK2)

NOTE:

For the diagnostic procedure, refer to DTC P2442. <Ref. to EN(H4DOTC)(diag)-453, DTC P2442 SECOND-

ARY AIR INJECTION SYSTEM SWITCHING VALVE STUCK OPEN (BANK2), Diagnostic Procedure with

Diagnostic Trouble Code (DTC).>

CHECK SECONDARY AIR COMBINATION
VALVE RELAY 1.
Measure the resistance between the secondary
air combination valve relay 1 terminals with the
battery disconnected.

Terminals

No. 3 — No. 4:

Is the resistance 1 MΩ or
more?

Go to step

17.

Replace the sec-
ondary air combina-
tion valve relay 1.
<Ref. to
EN(H4DOTC)(diag)
-9, Electrical Com-
ponent Location.>

CHECK SECONDARY AIR COMBINATION
VALVE RELAY 1 POWER SUPPLY.
1) Turn the ignition switch to ON.
2) Measure the voltage between the second-
ary air combination valve relay 1 connector and
chassis ground.

Connector & terminal

(F9) No. 4 (+) — Chassis ground (–):
(F9) No. 1 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step

18.

Repair the open or
ground short circuit
of power supply
circuit.

CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 1 CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the ECM connector.
3) Measure the resistance of harness between
ECM connector and secondary air combination
valve relay 1 connector.

Connector & terminal

(B135) No. 8 — (F9) No. 2:

Is the resistance less than 1 Ω? Go to step

19.

Repair the harness
and connector.
NOTE:

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

connector

and  secondary  air
combination  valve
relay 1 connector
• Poor  contact  of
coupling connector

CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 1 CONNECTOR.
Measure the resistance between the secondary
air combination valve relay 1 connector and
chassis ground.

Connector & terminal

(F9) No. 2 — Chassis ground:

Is the resistance 1 MΩ or
more?

Repair the poor
contact of ECM
connector.

Repair the short
circuit to ground in
harness between
ECM connector
and secondary air
combination valve
relay 1 connector.

Step

Check

Yes

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