Subaru Impreza 2003 Service Manual page 1411

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.
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(H4DOTC)-49, Com-
pulsory Valve Operation Check Mode.>
Connector & terminal
(B84) No. 17 (+) — Chassis ground ( − − − − ):
(B84) No. 28 (+) — Chassis ground ( − − − − ):
2 CHECK SHORT CIRCUIT IN RADIATOR FAN
RELAY CONTROL CIRCUIT.
1)Turn the ignition switch to OFF.
2)Remove the fan relay 1, fan relay 2 and fan
mode relay.
3)Disconnect the test mode connector.
4)Turn the ignition switch to ON.
5)Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B84) No. 17 (+) — Chassis ground ( − − − − ):
(B84) No. 28 (+) — Chassis ground ( − − − − ):
3 CHECK FAN RELAY 1.
1)Turn the ignition switch to OFF.
2)Remove the fan relay 1.
3)Measure the resistance between fan relay 1
terminals.
Terminals
No. 25 — No. 26:
4 CHECK FAN RELAY 2.
1)Remove the fan relay 2.
2)Measure the resistance between fan relay 2
terminals.
Terminals
No. 23 — No. 24:
5 CHECK POOR CONTACT.
Check poor contact in ECM connector.
Check
Does the voltage change 0 —
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(H4DOTC)-235
ENGINE (DIAGNOSTICS)
Yes
Even if malfunc- Go to step 2.
tion indicator light
lights up, the cir-
cuit has returned
to a normal condi-
tion 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(H4DOTC)-49,
Engine Control
Module (ECM).>
Replace the fan Go to step 4.
relay 1 and ECM.
<Ref. to
FU(H4DOTC)-49,
Engine Control
Module (ECM).>
Replace the fan Go to step 5.
relay 2 and ECM.
<Ref. to
FU(H4DOTC)-49,
Engine Control
Module (ECM).>
Repair the poor Replace the ECM.
contact in ECM <Ref. to
connector. FU(H4DOTC)-49,
Engine Control
Module (ECM).>
No