ENGINE (DIAGNOSTICS)(H4DO) > Diagnostic Procedure with Diagnostic Trouble Code (DTC)

DTC DETECTING CONDITION:

Detected when two consecutive driving cycles with fault occur.

TROUBLE SYMPTOM:

• Radiator fan does not operate properly.

• Overheating

CAUTION:

After repairing or replacing the defective part, perform the Clear Memory Mode and Inspection Mode .

WIRING DIAGRAM:

STEP	CHECK	YES	NO
1.CHECK OUTPUT SIGNAL OF 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) Measure the voltage between ECM terminal and chassis ground while operating the radiator fan relay. NOTE: The radiator fan relay can be operated using the Subaru Select Monitor. Regarding the procedures, refer to “Compulsory Valve Operation Check Mode”. Connector & terminal (B135) No. 19 (+) — Chassis ground (−):	Is the voltage 0 — 10 V?	Repair the poor contact of ECM connector.
2.CHECK GROUND SHORT CIRCUIT OF RADIATOR MAIN FAN RELAY CONTROL. 1) Turn the ignition switch to OFF. 2) Disconnect the connectors from the ECM. 3) Measure the resistance of harness between ECM connector and chassis ground. Connector & terminal (B135) No. 19 — Chassis ground:	Is the resistance less than 10 Ω?	Repair the ground short circuit of the radiator main fan relay control.
3.CHECK POWER SUPPLY TO RELAY. 1) Remove the main fan relay from the A/C relay holder. 2) Turn the ignition switch to ON. 3) Measure the voltage between fuse & relay box (F/B) connector and chassis ground. Connector & terminal (F27) No. 34 (+) — Chassis ground (−):	Is the voltage 10 V or more?		Repair the open circuit of harness between ignition switch and fuse & relay box (F/B) connector.
4.CHECK MAIN FAN RELAY. 1) Turn the ignition switch to OFF. 2) Measure the resistance between main fan relay terminals. Terminals No. 32 — No. 34:	Is the resistance between 87 — 107 Ω?		Replace the main fan relay.
5.CHECK OPEN CIRCUIT OF MAIN FAN RELAY CONTROL. Measure the resistance of harness between ECM and main fan relay connector. Connector & terminal (B135) No. 19 — (F27) No. 32:	Is the resistance less than 1 Ω?		Repair the harness and connector. NOTE: In this case, repair the following item: • Open circuit of harness between ECM and main fan relay connector • Poor contact of coupling connector
6.CHECK POOR CONTACT. Check poor contact of ECM or main fan relay connector.	Is there poor contact in ECM or main fan relay connector?	Repair poor contact in ECM or main fan relay connector.	Contact your SUBARU distributor service.