Subaru Impreza 2004 Service Manual page 154

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)(diag)-48,
Compulsory 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. 30 — No. 31:
4 CHECK FAN RELAY 2.
1)Remove the fan relay 2.
2)Measure the resistance between fan relay 2
terminals.
Terminals
No. 28 — No. 29:
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)(diag)-233
ENGINE (DIAGNOSTICS)
Yes
Even if malfunction Go to step 2.
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
radiator fan relay
control 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