Subaru Forester 2004 Service Manual page 176

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 2.5)-27, Subaru
Select Monitor.>
Connector & terminal
(B135) No. 24 (+) — Chassis ground (
(B135) No. 25 (+) — Chassis ground (
2 CHECK GROUND SHORT CIRCUIT IN RADI-
ATOR FAN RELAY CONTROL CIRCUIT.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness
between ECM connector and chassis ground.
Connector & terminal
(B135) No. 24 — Chassis ground:
(B135) No. 25 — Chassis ground:
3 CHECK POWER SUPPLY FOR RELAY.
1) Remove the main fan relay and sub 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
(F27) No. 27 (+) — Chassis ground (
(F27) No. 32 (+) — Chassis ground (
4 CHECK FAN RELAY.
1) Turn the ignition switch to OFF.
2) Measure the resistance between fan relay
terminals.
Terminals
No. 32 — No. 34 (Main fan relay)
No. 25 — No. 27 (Sub fan relay)
5 CHECK OPEN CIRCUIT IN FAN RELAY
CONTROL CIRCUIT.
Measure the resistance of harness between
ECM and fan relay connector.
Connector & terminal
(B135) No. 24 — (F27) No. 27:
(B135) No. 25 — (F27) No. 32:
6 CHECK POOR CONTACT.
Check poor contact in ECM or fan relay connector.
Check
Does the voltage vary between
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 less than 1
Ω?
Is there poor contact in ECM or
fan relay connector?
EN(H4DOTC 2.5)-175
ENGINE (DIAGNOSTIC)
Yes
Repair the poor Go to step 2.
contact in ECM
connector.
Go to step 3. Repair ground
short circuit in
radiator fan relay
control circuit.
Repair open circuit
in harness
between ignition
switch and fuse
and relay box (F/B)
connector.
Replace the fan
relay.
Go to step 6. 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
Repair the poor Contact the SUB-
contact in ECM or ARU dealer.
fan relay connector.
No