Subaru 2009 IMPREZA Service Manual page 492

Step
1 CHECK MAIN RELAY.
1) Turn the ignition switch to OFF.
2) Remove the main relay.
3) Connect the battery to main relay terminals
No. 39 and No. 40.
4) Measure the resistance between main relay
terminals.
Terminals
No. 37 — No. 38:
2 CHECK GROUND CIRCUIT FOR ECM.
1) Disconnect the connectors from ECM.
2) Measure the resistance of harness between
ECM and chassis ground.
Connector & terminal
(B134) No. 5 — Chassis ground:
(B137) No. 1 — Chassis ground:
(B137) No. 2 — Chassis ground:
(B137) No. 3 — Chassis ground:
(B137) No. 7 — Chassis ground:
3 CHECK INPUT VOLTAGE OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B135) No. 5 (+) — Chassis ground (–):
(B135) No. 19 (+) — Chassis ground (–):
4 CHECK INPUT VOLTAGE OF MAIN RELAY.
Measure the voltage between main relay con-
nector and chassis ground.
Connector & terminal
(B220) No. 37 (+) — Chassis ground (–):
(B220) No. 39 (+) — Chassis ground (–):
5 CHECK INPUT VOLTAGE OF ECM.
1) Turn the ignition switch to OFF.
2) Install the main relay.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 7 (+) — Chassis ground (–):
(B135) No. 2 (+) — Chassis ground (–):
6 CHECK INPUT VOLTAGE OF ECM.
1) Turn the ignition switch to OFF.
2) Connect the connector to ECM.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 7 (+) — Chassis ground (–):
(B135) No. 2 (+) — Chassis ground (–):
Diagnostics for Engine Starting Failure
Is the resistance less than 1 ? Go to step 2.
Is the resistance less than 5 ? Go to step 3.
Is the voltage 10 V or more?
Is the voltage 10 V or more?
Is the voltage 10 V or more?
Is the voltage 10 V or more?
EN(H4SO)(diag)-75
Check Yes
Go to step 4.
Go to step 5.
Go to step 6.
Check ignition con-
trol system. <Ref.
to
EN(H4SO)(diag)-
76, IGNITION
CONTROL SYS-
TEM, Diagnostics
for Engine Starting
Failure.>
ENGINE (DIAGNOSTICS)
No
Replace the main
relay. <Ref. to
FU(H4SO)-46,
Main Relay.>
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
• Open circuit of
harness between
ECM and engine
ground
• Poor contact of
coupling connector
Repair the open or
ground short circuit
of power supply
circuit.
Repair the open or
ground short circuit
of harness of
power supply cir-
cuit.
Repair the open or
ground short circuit
of harness
between ECM and
main relay connec-
tor.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and main re-
lay connector
• Poor contact of
main relay connec-
tor