Subaru Impreza 2004 Service Manual page 130

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
1 CHECK OUTPUT SIGNAL FROM ECM.
1)Turn the ignition switch to ON.
2)Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B137) No. 10 (+) — Chassis ground ( − − − − ):
2 CHECK POWER SUPPLY TO IDLE AIR CON-
TROL SOLENOID VALVE.
1)Turn the ignition switch to OFF.
2)Disconnect the connector from idle air con-
trol solenoid valve.
3)Turn the ignition switch to ON.
4)Measure the voltage between idle air control
solenoid valve and engine ground.
Connector & terminal
(E7) No. 2 (+) — Engine ground ( − − − − ):
3 CHECK HARNESS BETWEEN ECM AND
IDLE AIR CONTROL SOLENOID VALVE
CONNECTOR.
1)Turn the ignition switch to OFF.
2)Disconnect the connector from ECM.
3)Measure the resistance of harness between
ECM and idle air control solenoid valve con-
nector.
Connector & terminal
(B137) No. 10 — (E7) No. 1:
4 CHECK HARNESS BETWEEN ECM AND
IDLE AIR CONTROL SOLENOID VALVE
CONNECTOR.
Measure the resistance of harness between
ECM and chassis ground.
Connector & terminal
(B137) No. 10 — Chassis ground:
5 CHECK GROUND CIRCUIT OF IDLE AIR
CONTROL SOLENOID VALVE.
Measure the resistance of harness between
idle air control solenoid valve connector and
engine ground.
Connector & terminal
(E7) No. 3 — Engine ground:
6 CHECK POOR CONTACT.
Check poor contact in ECM and idle air control
solenoid valve connectors.
Check
Is the voltage more than 3 V?
Is the voltage more than 10 V? Go to step 3.
Is the resistance less than 1
Ω?
Is the resistance more than 1
MΩ?
Is the resistance less than 5
Ω?
Is there poor contact in ECM
and idle air control solenoid
valve connectors?
EN(H4DOTC)(diag)-209
ENGINE (DIAGNOSTICS)
Yes
Repair the poor Go to step 2.
contact in ECM
connector.
Repair the har-
ness and connec-
tor.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
idle air control
solenoid valve and
main relay connec-
tor
• Poor contact in
coupling connector
Go to step 4. Repair the har-
ness and connec-
tor.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
ECM and idle air
control solenoid
valve connector
• Poor contact in
coupling connector
Go to step 5. Repair the ground
short circuit in har-
ness between
ECM and idle air
control solenoid
valve connector.
Go to step 6. Repair the open
circuit in harness
between idle air
control solenoid
valve connector
and engine ground
cable.
Repair the poor Replace the idle
contact in ECM air control solenoid
and idle air control valve. <Ref. to
solenoid valve FU(H4DOTC)-36,
connectors. Idle Air Control
Solenoid Valve.>
No