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DTC P0481: Fan 2 Control Circuit: Notes

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 .

G16390503Courtesy of SUBARU OF AMERICA, INC.
G16390504Courtesy 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 .
  1. 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 in harness between ECM connector and sub fan motor connector, and between ECM connector and radiator fan control module (sub) connector.

      Connector & terminal 

      (B61) No. 41 - (Fr52) No. 1:

      (B61) No. 41 - (Fr34) No. 2:

    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
    • Open circuit in harness between ECM connector and radiator fan control module (sub) connector
    • Poor contact of ECM connector
    • Poor contact of sub fan motor connector
    • Poor contact of radiator fan control module (sub) connector
    • Poor contact of coupling connector
  2. CHECK HARNESS OF SUB FAN MOTOR DIAGNOSTIC SIGNAL (SHORT TO POWER SUPPLY)  .
    1. Turn the ignition switch to ON.
    2. Measure the voltage of harness between ECM connector and engine ground.

      Connector & terminal 

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

    Is the voltage less than 1 V?

    Yes  : Go to  3.

    No  : Repair the following item.

    • Short circuit to power supply in harness between ECM connector and sub fan motor connector
    • Short circuit to power supply in harness between ECM connector and radiator fan control module (sub) connector
  3. CHECK HARNESS BETWEEN RADIATOR FAN CONTROL MODULE (SUB) AND SUB FAN MOTOR (MOTOR DOWNSTREAM) (OPEN)  .
    1. Turn the ignition switch to OFF.
    2. Measure the resistance of harness between radiator fan control module (sub) connector and sub fan motor connector.

      Connector & terminal 

      (Fr34) No. 1 - (Fr52) No. 2:

    Is the resistance less than 1 Ω?

    Yes  : Go to  4.

    No  : Repair the following item.

    • Open circuit in harness between radiator fan control module (sub) connector and sub fan motor connector
    • Poor contact of radiator fan control module (sub) connector
    • Poor contact of sub fan motor connector
    • Poor contact of coupling connector
  4. CHECK HARNESS BETWEEN RADIATOR FAN CONTROL MODULE (SUB) AND SUB FAN MOTOR (MOTOR DOWNSTREAM) (SHORT TO POWER SUPPLY)  .
    1. Turn the ignition switch to ON.
    2. Measure the voltage of harness between radiator fan control module (sub) connector and engine ground.

      Connector & terminal 

      (Fr34) No. 1 (+) - Engine ground (-):

    Is the voltage less than 1 V?

    Yes  : Go to  5.

    No  : Repair the short circuit to power supply in harness between radiator fan control module (sub) connector and sub fan motor connector.

  5. CHECK HARNESS BETWEEN RADIATOR FAN CONTROL MODULE (SUB) AND CHASSIS GROUND (OPEN)  .
    1. Turn the ignition switch to OFF.
    2. Measure the resistance of harness between radiator fan control module (sub) connector and engine ground.

      Connector & terminal 

      (Fr33) No. 1 - Engine ground:

    Is the resistance less than 1 Ω?

    Yes  : Go to  6.

    No  : Repair the following item.

    • Open circuit in harness between radiator fan control module (sub) connector and engine ground
    • Poor contact of radiator fan control module (sub) connector
    • Poor contact of engine ground
    • Poor contact of coupling connector
  6. CHECK HARNESS OF SUB FAN MOTOR DRIVE SIGNAL CIRCUIT (SHORT TO POWER SUPPLY)  .
    1. Turn the ignition switch to ON.
    2. Measure the voltage of harness between ECM connector and engine ground.

      Connector & terminal 

      (B61) No. 27 (+) - Engine ground (-):

    Is the voltage less than 1 V?

    Yes  : Replace the radiator fan control module (sub). Ref. to COOLING (H4DOTC)>RADIATOR FAN AND FAN MOTOR ASSEMBLY .

    No  : Repair the short circuit to power supply in harness between ECM connector and radiator fan control module (sub) connector.

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