DTC P0481: Fan 2 Control Circuit: Notes

1. -

DTC detecting condition:

Detected when two consecutive driving cycles with fault occur.

Trouble symptom:

The radiator fan keeps rotating.

Wiring diagram:

Engine Electrical System Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM

Courtesy of SUBARU OF AMERICA, INC.

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD

NOTE:

After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE

CHECK HARNESS OF RADIATOR SUB FAN DIAGNOSTIC SIGNAL (OPEN) .
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Disconnect the connector from the sub fan motor.
4. Disconnect the connector from radiator fan control module (sub).
5. Measure the resistance between ECM connector and sub fan motor connector.
  Connector & terminal
  
  (B61) No. 41 - (Fr52) No. 1:
Is the resistance less than 1 Ω?

Yes : Go to 2.

No : Repair the following item.
- Open circuit in harness between ECM connector and sub fan motor connector
- Poor contact of coupling connector
CHECK HARNESS OF RADIATOR SUB FAN DIAGNOSTIC SIGNAL (SHORT TO GROUND) .
Measure the resistance between the ECM connector and engine ground.

Connector & terminal

(B61) No. 41 (+) - Engine ground (-):

Is the resistance 1 MΩ or more?

Yes : Go to 3.

No : Repair the short circuit to ground in harness between ECM connector and sub fan motor or radiator fan control unit (sub) connector.
CHECK SUB FAN RELAY .
1. Remove the sub fan relay from M/B.
2. Check the sub fan relay. Ref. to COOLING (H4DOTC)>RADIATOR FAN RELAY>INSPECTION
Is the check result OK?

Yes : Go to 4.

No : Replace the sub fan relay. Ref. to COOLING (H4DOTC)>RADIATOR FAN RELAY
CHECK POWER SUPPLY FOR RADIATOR FAN CONTROL UNIT (SUB) .
1. Connect the connector to ECM.
2. Turn the ignition switch to ON.
3. Measure the voltage between the sub fan relay and engine ground.
  Terminals
  
  No. 1 (+) - Engine ground (-):
  
  No. 2 (+) - Engine ground (-):
Is the voltage 10 V or more?

Yes : Go to 5.

No : Repair the following item.
- Open circuit or short circuit to ground in harness between M/B and sub fan relay
- Blown out of fuse
- Poor contact of MB-IG relay
CHECK POWER SUPPLY FOR RADIATOR FAN CONTROL UNIT (SUB) .
1. Turn the ignition switch to OFF.
2. Install the sub fan relay.
3. Turn the ignition switch to ON.
4. Measure the voltage between radiator fan control unit (sub) connector and engine ground.
  Connector & terminal
  
  (Fr33) No. 1 (+) - Engine ground (-):
Is the voltage 10 V or more?

Yes : Go to 6.

No : Repair the following item.
- Open circuit or short circuit to ground in harness between the sub fan relay and radiator fan control module (sub) connector
- Open circuit or short circuit to ground in harness between the sub fan relay and ECM connector
- Poor contact of coupling connector
- Poor contact of sub fan relay
CHECK HARNESS OF ECM AND RADIATOR FAN CONTROL UNIT (SUB) (SHORT TO POWER SUPPLY) .
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Measure the voltage between ECM connector and engine ground.
  Connector & terminal
  
  (B61) No. 27 (+) - Engine ground (-):
Is the voltage 10 V or more?

Yes : Repair the power supply short circuit of harness between ECM and radiator fan control unit (sub) connector.

No : Replace the radiator fan control module (sub). Ref. to COOLING (H4DOTC)>RADIATOR FAN CONTROL UNIT