Subaru 2002 IMPREZA Service Manual page 637

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK OUTPUT SIGNAL FROM ECM.
1)Turn the ignition switch to OFF.
2)Connect the test mode connector at the
lower portion of instrument panel (on the
driver's side).
3)Turn the ignition switch to ON.
4)While operating the radiator fan relay, mea-
sure the voltage between ECM terminal and
ground.
NOTE:
Radiator fan relay operation can be executed
using the Subaru Select Monitor. For proce-
dure, refer to "Compulsory Valve Operation
Check Mode".<Ref. to EN-34, Subaru Select
Monitor.>
Connector & terminal
(B134) No. 3 (+) — Chassis ground ( − − − − ):
2 CHECK GROUND SHORT CIRCUIT IN RADI-
ATOR MAIN FAN RELAY CONTROL CIR-
CUIT.
1)Turn the ignition switch to OFF.
2)Disconnect the connectors from ECM.
3)Measure the resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B134) No. 3 — Chassis ground:
3 CHECK POWER SUPPLY FOR RELAY.
1)Remove the main fan relay from A/C relay
holder.
2)Turn the ignition switch to ON.
3)Measure the voltage between fuse and relay
box (F/B) connector and chassis ground.
Connector & terminal
(F66) No. 28 (+) — Chassis ground ( − − − − ):
4 CHECK MAIN FAN RELAY.
1)Turn the ignition switch to OFF.
2)Measure the resistance between main fan
relay terminals.
Terminal
No. 28 — No. 27:
5 CHECK OPEN CIRCUIT IN MAIN FAN RE-
LAY CONTROL CIRCUIT.
Measure the resistance of harness between
ECM and main fan relay connector.
Connector & terminal
(B134) No. 3 — (F66) No. 27:
6 CHECK POOR CONTACT.
Check poor contact in ECM or main fan relay
connector.
Check
Does voltage change between
0 and 10 V?
Is the resistance less than 10
Ω?
Is the voltage more than 10 V? Go to step 4.
Is the resistance between 87
and 107 Ω?
Is the resistance less than 1
Ω?
Is there poor contact in ECM or
main fan relay connector?
EN-205
ENGINE (DIAGNOSTICS)
Yes
Repair the poor Go to step 2.
contact in ECM
connector.
Repair the ground Go to step 3.
short circuit in radi-
ator main fan relay
control circuit.
Repair the open
circuit in harness
between ignition
switch and fuse
and relay box (F/B)
connector.
Go to step 5. Replace the main
fan relay.
Go to step 6. Repair the har-
ness and connec-
tor.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
ECM and main fan
relay connector
• Poor contact in
coupling connector
(F45)
Repair the poor Contact with your
contact in ECM or Subaru distributor
main fan relay service.
connector.
No