Subaru 2002 IMPREZA Service Manual page 501

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
(B136) No. 21 — Chassis ground:
(B136) No. 22 — Chassis ground:
(B134) No. 27 — Chassis ground:
(B134) No. 8 — Chassis ground:
(B134) No. 7 — Chassis ground:
(B134) No. 34 — Chassis ground:
(B134) No. 35 — Chassis ground:
(B135) No. 25 — Chassis ground: (MT
vehicle)
(B135) No. 6 — Chassis ground: (AT
vehicle)
3 CHECK INPUT VOLTAGE OF ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) 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
(B135) No. 7 (+) — 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
(B135) No. 19 — 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
(B135) No. 19 (+) — 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-69
ENGINE (DIAGNOSTICS)
Yes
Go to step 3. Repair the open
circuit in harness
between ECM
connector and
engine grounding
terminal.
Repair the open or
ground short cir-
cuit of power sup-
ply circuit.
Repair the open or
ground short cir-
cuit of power sup-
ply circuit.
Go to step 6. Repair the ground
short circuit in har-
ness between
ECM connector
and main relay
connector, then
replace the ECM.
Replace the ECM.
Repair the open
circuit in harness
between ECM
connector and
main relay con-
nector.
Go to step 9. Repair the open
circuit between
main relay and
chassis ground.
Repair the open or
ground short cir-
cuit in harness of
power supply cir-
cuit.
No