Seat Heater Does Not Operate According To The Last Memory

Trouble symptom:

The ignition switch was turned from ON to OFF while the seat heater was in operation, and then was turned from OFF to ON. However, the operation does not start in the operating condition the same as before turning the ignition switch OFF.

Trouble causes:

Seat ventilation control module failure
A/C control module failure
Seat ventilation circuit failure
Seat heater circuit failure
Center information display failure
Cockpit control module failure
Heater failure

Wiring diagram:

Seat heater system Ref. to WIRING SYSTEM>SEAT HEATER SYSTEM>WIRING DIAGRAM .

Seat ventilation system Ref. to WIRING SYSTEM>SEAT VENTILATION SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

Courtesy of SUBARU OF AMERICA, INC.

CAUTION: Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to VENTILATION SEAT (DIAGNOSTICS)>General Description>CAUTION .

CHECK OPERATION CONDITION .
1. Turn the ignition switch to ON.
2. Activate the seat heater.
3. Turn the ignition switch to OFF with the seat heater ON.
4. Turn the ignition switch to ON again.
  NOTE: When turning the ignition switch to ON using the telematics, check that seat heater operation commands are not issued.
  
  Is the seat heater operation condition the same as before turning the ignition switch OFF?
  
  Yes: The circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.
  
  No: Go to 2 .
CHECK DTC .
1. Turn the ignition switch to ON.
2. Read the following DTCs using Subaru Select Monitor. Ref. to Ventilation Seat (Diagnostics)>Diagnostic Trouble Code (DTC) . Ref. to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) . Ref. to AIR CONDITIONER (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) . Ref. to COCKPIT CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) . Ref. to TELEMATICS SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
  - Ventilation Seat
  - Body Control
  - Air Conditioner
  - Cockpit Control
  - Telematics
  Are any DTCs displayed?
  
  Yes: Perform the diagnosis for the displayed DTCs. Ref. to Ventilation Seat (Diagnostics)>Diagnostic Trouble Code (DTC) . Ref. to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) . Ref. to AIR CONDITIONER (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) . Ref. to COCKPIT CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) . Ref. to TELEMATICS SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
  
  No: Go to 3 .
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) (i 108), seat connectors (L57) (R57), coupling connectors (B43) (L51) (R51), and heater connectors (St27) (St28).
  Is the check result OK?
  
  Yes: Go to 4 .
  
  No: Repair the connector.
CHECK CAN COMMUNICATION LINE .
Inspect LAN system. Ref. to LAN SYSTEM (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .

Is the check result OK?

Yes: Go to 5 .

No: Perform the inspection according to the diagnosis for LAN system. Ref. to LAN SYSTEM (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .
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 and 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 6 .
  
  No: Repair or replace the open circuit of harness.
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 and 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 7 .
  
  No: Repair or replace the open circuit of harness.
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 and 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 8 .
  
  No: Repair or replace the open circuit of harness.
CHECK CENTER INFORMATION DISPLAY .
1. Connect all connectors.
2. Turn the ignition switch to ON.
3. Start the engine.
4. Touch the seat heater switch, and check if the display for seat heater operation mode changes.
  Does the display change?
  
  Yes: Go to 9 .
  
  No: Ref. to VENTILATION SEAT (DIAGNOSTICS)>DIAGNOSTICS WITH PHENOMENON>INSPECTION>DISPLAY DOES NOT CHANGE ALONG WITH SEAT HEATER SWITCH OPERATION .
CHECK OPERATION MODE .
1. Touch the seat heater switch.
2. Using the Subaru Select Monitor, check the following items in the [Data monitor] of [Ventilation Seat]. Ref. 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 10 .
  
  No: Ref. to VENTILATION SEAT (DIAGNOSTICS)>DIAGNOSTICS WITH PHENOMENON>INSPECTION>SEAT HEATER LEVEL DOES NOT CHANGE (DISPLAY CHANGES, BUT OPERATION DOES NOT CHANGE) .
CHECK SEAT HEATER .
1. Start the engine.
2. Activate the seat heater.
3. After a predetermined period of time, check if the backrest and cushion are both heated.
  Are both the backrest 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: Ref. to VENTILATION SEAT (DIAGNOSTICS)>DIAGNOSTICS WITH PHENOMENON>INSPECTION>SEAT HEATER ON ONE SIDE (BACKREST SIDE OR CUSHION SIDE) DOES NOT OPERATE .