Subaru 2002 IMPREZA Service Manual page 1485

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 and chassis
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(TURBO)-46, Com-
pulsory Valve Operation Check Mode.>
Connector & terminal
(B137) No. 17 (+) — Chassis ground ( − − − − ):
(B137) No. 28 (+) — Chassis ground ( − − − − ):
2 CHECK SHORT CIRCUIT IN RADIATOR FAN
RELAY CONTROL CIRCUIT.
1)Turn the ignition switch to OFF.
2)Remove the main fan relay and sub fan
relay. (with A/C models)
3)Disconnect the test mode connector.
4)Turn the ignition switch to ON.
5)Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B137) No. 17 (+) — Chassis ground ( − − − − ):
(B137) No. 28 (+) — Chassis ground ( − − − − ):
3 CHECK MAIN FAN RELAY.
1)Turn the ignition switch to OFF.
2)Remove the main fan relay 1 and 2.
3)Measure the resistance between main fan
relay terminals.
Terminal
No. 25 — No. 26 (Main fan relay 1)
No. 23 — No. 24 (Main fan relay 2)
4 CHECK SUB FAN RELAY.
1)Remove the sub fan relay.
2)Measure the resistance between sub fan
relay terminals.
Terminal
No. 7 — No. 8 (Sub fan relay 1)
No. 17 — No. 18 (Sub fan relay 2)
5 CHECK POOR CONTACT.
Check poor contact in ECM connector.
Check
Does the voltage change
between 0 and 10 V?
Is the voltage more than 10 V? Repair the battery
Is the resistance less than 1
Ω?
Is the resistance less than 1
Ω?
Is there poor contact in ECM
connector?
EN(TURBO)-325
ENGINE (DIAGNOSTICS)
Yes
Even if MIL lights Go to step 2.
up, the circuit has
returned to a nor-
mal condition at
this time. In this
case, repair the
poor contact in
ECM connector.
Go to step 3.
short circuit in radi-
ator fan relay con-
trol circuit. After
repair, replace the
ECM. <Ref. to
FU(TURBO)-49,
Engine Control
Module.>
Replace the main Go to step 4.
fan relay and
ECM. <Ref. to
FU(TURBO)-49,
Engine Control
Module.>
Replace the sub Go to step 5.
fan relay and
ECM. <Ref. to
FU(TURBO)-49,
Engine Control
Module.>
Repair the poor Replace the ECM.
contact in ECM <Ref. to
connector. FU(TURBO)-49,
Engine Control
Module.>
No