Subaru Impreza 2003 Service Manual page 475

DIAGNOSTICS FOR ENGINE STARTING FAILURE
Step
2 CHECK GROUND CIRCUIT OF ECM.
1)Disconnect the connector from ECM.
2)Measure the resistance of harness between
ECM and chassis ground.
Connector & terminal
(B134) No. 7 — Chassis ground:
(B134) No. 35 — Chassis ground:
(B135) No. 21 — Chassis ground:
(B136) No. 5 — Chassis ground:
(B136) No. 16 — Chassis ground:
(B136) No. 26 — Chassis ground:
(B137) No. 14 — Chassis ground:
(B136) No. 19 — Chassis ground: (MT
model)
3 CHECK INPUT VOLTAGE OF ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B135) No. 9 (+) — Chassis ground (–):
4 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
(B136) No. 10 (+) — Chassis ground (–):
5 CHECK HARNESS BETWEEN ECM AND
MAIN RELAY CONNECTOR.
1)Turn the ignition switch to OFF.
2)Measure the resistance between ECM and
chassis ground.
Connector & terminal
(B136) No. 12 — Chassis ground:
6 CHECK OUTPUT VOLTAGE FROM ECM.
1)Connect the connector to ECM.
2)Turn the ignition switch to ON.
3)Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 12 (+) — Chassis ground (–):
7 CHECK INPUT VOLTAGE OF MAIN RELAY.
Check the voltage between main relay connec-
tor and chassis ground.
Connector & terminal
(B47) No. 2 (+) — Chassis ground (–):
8 CHECK GROUND CIRCUIT OF MAIN RE-
LAY.
1)Turn the ignition switch to OFF.
2)Measure the resistance between main relay
connector and chassis ground.
Connector & terminal
(B47) No. 1 — Chassis ground:
9 CHECK INPUT VOLTAGE OF MAIN RELAY.
Measure the voltage between main relay con-
nector and chassis ground.
Connector & terminal
(B47) No. 5 (+) — Chassis ground ( − − − − ):
(B47) No. 6 (+) — Chassis ground ( − − − − ):
Check
Is the resistance less than 5
Ω?
Is the voltage more than 10 V? Go to step 4.
Is the voltage more than 10 V? Go to step 5.
Is the resistance more than 1
MΩ?
Is the voltage more than 10 V? Go to step 7.
Is the voltage more than 10 V? Go to step 8.
Is the resistance less than 5
Ω?
Is the voltage more than 10 V? Go to step 10.
EN(H4SO)-63
ENGINE (DIAGNOSTICS)
Yes
Go to step 3. Repair open circuit
in harness
between ECM
connector and
engine grounding
terminal.
Repair open or
ground short cir-
cuit of power sup-
ply circuit.
Repair open or
ground short cir-
cuit of power sup-
ply circuit.
Go to step 6. Repair ground
short circuit in har-
ness between
ECM connector
and main relay
connector, then
replace the ECM.
Replace the ECM.
Repair open circuit
in harness
between ECM
connector and
main relay con-
nector.
Go to step 9. Repair open circuit
between main
relay and chassis
ground.
Repair open or
ground short cir-
cuit in harness of
power supply cir-
cuit.
No