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Seat Heater Cannot Be Operated

Trouble symptom: 

Seat heater cannot be operated.

Trouble causes: 

Wiring diagram: 

Seat ventilation system. Refer to WIRING SYSTEM>Seat Ventilation System>WIRING DIAGRAM .

Seat heater system. Refer to WIRING SYSTEM>Seat Heater System>WIRING DIAGRAM .

G13630739Courtesy of SUBARU OF AMERICA, INC.
G13630742Courtesy of SUBARU OF AMERICA, INC.
CAUTION: Before performing diagnosis, refer to "CAUTION" in "General Description". Refer to VENTILATION SEAT (DIAGNOSTICS)>General Description>CAUTION .
  1. CHECK SEAT SPECIFICATION  .

    Check the vehicle specification.

    Is this vehicle equipped with seat ventilation?

    Yes  : Go to  2.

    No  : Perform the inspection according to the [Air Conditioner] diagnosis. Refer to AIR CONDITIONER (DIAGNOSTICS)>Basic Diagnostic Procedure .

    NOTE: For the specification without seat ventilation, the seat heater is controlled by A/C Control Module.
  2. CHECK SEAT VENTILATION SWITCH DISPLAY  .
    1. Turn the ignition switch to ON.
    2. Touch the driver's side and passenger's side seat indicators on the center information display.
    3. Check if the seat ventilation switch is displayed under the seat heater switch.

    Is the seat ventilation switch displayed?

    Yes  : Go to  3.

    No  : Refer to VENTILATION SEAT (DIAGNOSTICS)>Diagnostics with Phenomenon>INSPECTION>SEAT VENTILATION SWITCH IS NOT DISPLAYED .

  3. IDENTIFY SEATS WITH THE SEAT HEATER NOT FUNCTIONING  .
    1. Start the engine.
    2. Operate the driver's side and passenger's side seat heaters.
    3. After a predetermined period of time, check if the seat heater is operating.

    Is the side which is not functioning either one of the driver's side or passenger's side only?

    Yes  : Go to  6.

    No  : When both the driver's side and passenger's side are not functioning, Go to  4.

  4. CHECK DTC  .
    1. Turn the ignition switch to ON.
    2. Read the following DTCs using Subaru Select Monitor. Refer to VENTILATION SEAT (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) . Refer to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) . Refer to AIR CONDITIONER (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) . Refer to COCKPIT CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
    • Ventilation Seat
    • Body Control
    • Air Conditioner
    • Cockpit Control

    Are any DTCs displayed?

    Yes  : Perform the diagnosis for the displayed DTCs. Refer to VENTILATION SEAT (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) . Refer to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) . Refer to AIR CONDITIONER (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) . Refer to COCKPIT CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

    No  : Go to  5.

  5. CHECK CONNECTOR  .
    1. Turn the ignition switch to OFF.
    2. Check malfunctions (terminal bends, connection status, etc.) of the seat ventilation Control Module connector (St41), A/C Control Module connectors (i107) (i108), seat connectors (L57) (R57), coupling connectors (B43) (L51) (R51), and heater connectors (St27) (St28).

    Is the check result OK?

    Yes  : Go to  6.

    No  : Repair the connector.

  6. CHECK HARNESS (OPEN CIRCUIT)  .
    1. Disconnect the driver's side seat connector (L57) and passenger's side seat connector (R57).
    2. Turn the ignition switch to ON.
    3. Using the tester, measure the voltage between terminals.

    Connector & terminal 

    Driver's side 

    (L57) No. 9 (+) - Chassis ground (-):

    Passenger's side 

    (R57) No. 9 (+) - Chassis ground (-):

    Is the voltage 10 V or more?

    Yes  : Go to  7.

    No  : Repair or replace the open circuit of harness.

  7. CHECK HARNESS (OPEN CIRCUIT)  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the A/C Control Module connectors (i107) and (i108).
    3. Using the tester, measure the resistance between terminals.

    Connector & terminal 

    Driver's side 

    (L57) No. 10 - (i108) No. 7:

    (L57) No. 15 - (i108) No. 1:

    (L57) No. 16 - (i107) No. 15:

    Passenger's side 

    (R57) No. 10 - (i108) No. 7:

    (R57) No. 15 - (i108) No. 5:

    (R57) No. 16 - (i107) No. 14:

    Is the resistance less than 5 Ω?

    Yes  : Go to  8.

    No  : Repair or replace the open circuit of harness.

  8. CHECK HARNESS (OPEN CIRCUIT)  .
    1. Disconnect the driver's side heater connector (St28) and passenger's side heater connector (St27).
    2. Using the tester, measure the resistance between terminals.

    Connector & terminal 

    Driver's side 

    (St28) No. 1 - (St2) No. 9:

    (St28) No. 2 - (St2) No. 15:

    (St28) No. 3 - (St2) No. 16:

    (St28) No. 4 - (St2) No. 10:

    Passenger's side 

    (St27) No. 1 - (St1) No. 9:

    (St27) No. 2 - (St1) No. 15:

    (St27) No. 3 - (St1) No. 16:

    (St27) No. 4 - (St1) No. 10:

    Is the resistance less than 5 Ω?

    Yes  : Go to  9.

    No  : Repair or replace the open circuit of harness.

  9. CHECK CENTER INFORMATION DISPLAY  .
    1. Connect all connectors.
    2. Turn the ignition switch to ON.
    3. Touch the seat heater switch on the center information display, and check if the display for seat heater operation mode changes.

    Does the display change?

    Yes  : Go to  10.

    No  : Refer to VENTILATION SEAT (DIAGNOSTICS)>Diagnostics with Phenomenon>INSPECTION>DISPLAY DOES NOT CHANGE ALONG WITH SEAT HEATER SWITCH OPERATION .

  10. CHECK OPERATION MODE  .
    1. Start the engine.
    2. Touch the seat heater switch.
    3. Using the Subaru Select Monitor, check the following items in the [Data monitor] of [Ventilation Seat]. Refer to VENTILATION SEAT (DIAGNOSTICS)>Data Monitor .
    • Seat Heater Operation Steps(Driver's)
    • Seat Heater Operation Steps(Passenger's)

    Does the operation mode change?

    Yes  : Go to  11.

    No  : Refer to VENTILATION SEAT (DIAGNOSTICS)>DIAGNOSTICS WITH PHENOMENON>INSPECTION>SEAT HEATER LEVEL DOES NOT CHANGE (DISPLAY CHANGES, BUT OPERATION DOES NOT CHANGE) .

  11. CHECK SEAT HEATER  .
    1. Activate the seat heater.
    2. After a predetermined period of time, check if the back rest and cushion are both heated.

    Are both the back rest side and cushion side operating?

    Yes  : Even if DTC is displayed, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

    NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.

    No  : Refer to VENTILATION SEAT (DIAGNOSTICS)>DIAGNOSTICS WITH PHENOMENON>INSPECTION>SEAT HEATER ON ONE SIDE (BACK REST SIDE OR CUSHION SIDE) DOES NOT OPERATE .

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