Subaru Impreza 2003 Service Manual page 1407

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 voltage between ECM terminal and
ground.
NOTE:
Radiator fan relay operation can be executed
using Subaru Select Monitor. For procedure,
refer to "Compulsory Valve Operation Check
Mode". <Ref. to EN(H4DOTC)-32, Subaru Se-
lect Monitor.>
Connector & terminal
(B84) No. 17 (+) — Chassis ground ( − − − − ):
(B84) No. 28 (+) — Chassis ground ( − − − − ):
2 CHECK GROUND SHORT CIRCUIT IN RADI-
ATOR FAN RELAY CONTROL CIRCUIT.
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
(B84) No. 17 — Chassis ground:
(B84) No. 28 — Chassis ground:
3 CHECK POWER SUPPLY FOR RELAY.
1)Remove the fan relay 1 and fan relay 2 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
(F27) No. 27 (+) — Chassis ground ( − − − − ):
(F27) No. 22 (+) — Chassis ground ( − − − − ):
4 CHECK FAN RELAY 1.
1)Turn the ignition switch to OFF.
2)Measure the resistance between fan relay 1
terminals.
Terminals
No. 27 — No. 28:
5 CHECK FAN RELAY 2.
1)Turn the ignition switch to OFF.
2)Measure the resistance between fan relay 2
terminals.
Terminals
No. 22 — No. 21:
6 CHECK OPEN CIRCUIT IN FAN RELAY
CONTROL CIRCUIT.
Measure the resistance of harness between
ECM and fan relay connector.
Connector & terminal
(B84) No. 17 — (F27) No. 28:
(B84) No. 28 — (F27) No. 21:
Check
Does the voltage change 0 —
10 V?
Is the resistance more than 1
MΩ?
Is the voltage more than 10 V? Go to step 4.
Is the resistance 87 — 107 Ω? Go to step 5.
Is the resistance 87 — 107 Ω? Go to step 6.
Is the resistance less than 1
Ω?
EN(H4DOTC)-231
ENGINE (DIAGNOSTICS)
Yes
Repair poor con- Go to step 2.
tact in ECM con-
nector.
Go to step 3. Repair ground
short circuit in radi-
ator fan relay con-
trol circuit.
Repair open circuit
in harness
between ignition
switch and fuse
and relay box (F/
B) connector.
Replace the fan
relay 1.
Replace the fan
relay 2.
Go to step 7. Repair harness
and connector.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
ECM and fan relay
connector
• Poor contact in
coupling connector
No