Subaru IMPREZA 2004 Service Manual page 742

ENGINE (DIAGNOSTICS)
Step
1 CHECK IGNITION SYSTEM FOR SPARKS.
1)Remove the plug cord cap from each spark
plug.
2)Install new spark plug on the plug cord cap.
CAUTION:
Do not remove the spark plug from engine.
3)Contact the spark plug's thread portion on
engine.
4)While opening the throttle valve fully, crank
engine to check that spark occurs at each cyl-
inder.
2 CHECK POWER SUPPLY CIRCUIT FOR IG-
NITION COIL & IGNITOR ASSY.
1)Turn the ignition switch to OFF.
2)Disconnect the connector from ignition coil &
ignitor ASSY.
3)Turn the ignition switch to ON.
4)Measure the power supply voltage between
ignition coil & ignitor ASSY connector and
engine ground.
Connector & terminal
1.6 L
(E12) No. 1 (+) — Engine ground ( − − − − ):
2.0 L and 2.5 L
(E12) No. 2 (+) — Engine ground ( − − − − ):
3 CHECK HARNESS OF IGNITION COIL & IG-
NITOR ASSY GROUND CIRCUIT.
1)Turn the ignition switch to OFF.
2)Measure the resistance between ignition coil
& ignitor ASSY connector and engine ground.
Connector & terminal
(E12) No. 3 — Engine ground:
4 CHECK IGNITION COIL & IGNITOR ASSY.
1)Remove the spark plug cords.
2)Measure the resistance between spark plug
cord contact portions to check secondary coil.
Terminals
1.6 L
No. 4 — No. 1:
2.0 L and 2.5 L
No. 1 — No. 2:
5 CHECK IGNITION COIL & IGNITOR ASSY.
Measure the resistance between spark plug
cord contact portions to check secondary coil.
Terminals
1.6 L
No. 3 — No. 2:
2.0 L and 2.5 L
No. 3 — No. 4:
Diagnostics for Engine Starting Failure
Does spark occur at each cyl-
inder?
Is the voltage more than 10 V? Go to step 3.
Is the resistance less than 5
Ω?
Is the resistance 10 — 15 Ω?
Is the resistance 10 — 15 Ω?
EN(H4SOw/oOBD)(diag)-46
Check
Check the fuel
pump system.
<Ref. to
EN(H4SOw/
oOBD)(diag)-49,
FUEL PUMP CIR-
CUIT, Diagnostics
for Engine Start-
ing Failure.>
Go to step 4.
Go to step 5.
Go to step 6.
Yes No
Go to step 2.
Repair the har-
ness and connec-
tor.
NOTE:
In this case, repair
the following:
• Open circuit or
ground short in
harness between
ignition coil & igni-
tor ASSY, and igni-
tion switch
connector
• Poor contact in
coupling connector
(B22)
Repair the har-
ness and connec-
tor.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
ignition coil & igni-
tor ASSY connec-
tor and engine
grounding terminal
Replace the igni-
tion coil & ignitor
ASSY.
Replace the igni-
tion coil & ignitor
ASSY.