Subaru 2009 IMPREZA Service Manual page 1297

ENGINE (DIAGNOSTICS)
Step
1 CHECK SPARK PLUG CONDITION.
1) Remove the spark plug. <Ref. to
IG(H4DOTC)-4, REMOVAL, Spark Plug.>
2) Check the spark plug condition. <Ref. to
IG(H4DOTC)-5, INSPECTION, Spark Plug.>
2 CHECK IGNITION SYSTEM FOR SPARKS.
1) Connect the spark plug to ignition coil.
2) Release the fuel pressure. <Ref. to
FU(H4DOTC)-60, RELEASING OF FUEL
PRESSURE, PROCEDURE, Fuel.>
3) Contact the spark plug thread portion to
engine.
4) While opening the throttle valve fully, crank
the engine to check that spark occurs at each
cylinder.
3 CHECK POWER SUPPLY CIRCUIT OF IGNI-
TION COIL.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ignition coil.
3) Turn the ignition switch to ON.
4) Measure the power supply voltage between
ignition coil connector and engine ground.
Connector & terminal
(E31) No. 3 (+) — Engine ground (–):
(E32) No. 3 (+) — Engine ground (–):
(E33) No. 3 (+) — Engine ground (–):
(E34) No. 3 (+) — Engine ground (–):
4 CHECK HARNESS OF IGNITION COIL
GROUND CIRCUIT.
1) Turn the ignition switch to OFF.
2) Measure the resistance between ECM and
ignition coil connector.
Connector & terminal
(E31) No. 2 — (B137) No. 6:
(E32) No. 2 — (B137) No. 6:
(E33) No. 2 — (B137) No. 6:
(E34) No. 2 — (B137) No. 6:
(E31) No. 2 — (B137) No. 26:
(E32) No. 2 — (B137) No. 26:
(E33) No. 2 — (B137) No. 26:
(E34) No. 2 — (B137) No. 26:
5 CHECK HARNESS BETWEEN ECM AND IG-
NITION COIL CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
ignition coil.
3) Measure the resistance of harness between
ECM and ignition coil connector.
Connector & terminal
(B137) No. 18 — (E31) No. 1:
(B137) No. 19 — (E32) No. 1:
(B137) No. 20 — (E33) No. 1:
(B137) No. 21 — (E34) No. 1:
Diagnostics for Engine Starting Failure
Is the spark plug condition nor-
mal?
Does spark occur at each cylin-
der?
Is the voltage 10 V or more?
Is the resistance less than 1 ? Go to step 5.
Is the resistance less than 1 ? Go to step 6.
EN(H4DOTC)(diag)-76
Check Yes
Go to step 2.
Check fuel pump
system. <Ref. to
EN(H4DOTC)(diag)
-78, FUEL PUMP
CIRCUIT, Diagnos-
tics for Engine
Starting Failure.>
Go to step 4.
No
Replace the spark
plug. <Ref. to
IG(H4DOTC)-4,
Spark Plug.>
Go to step 3.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ignition coil con-
nector and ignition
switch connector
• Poor contact of
coupling connector
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
• Open circuit of
harness between
ECM and ignition
coil connector
• Poor contact of
coupling connector
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
• Open circuit of
harness between
ECM and ignition
coil connector
• Poor contact of
coupling connector