DTC B1440: Air Mix Door Actuator Circuit Open (Driver)

DTC detecting condition: 

Air mix door actuator potentiometer circuit is open.

Trouble symptom: 

• Temperature cannot be adjusted for model without left/right independent air conditioner.
• Temperature of the driver's side cannot be adjusted for model with left/right independent air conditioner.

Wiring diagram: 

Air conditioning system Ref. to WIRING SYSTEM (IMPREZA MODEL)>AIR CONDITIONING SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>AIR CONDITIONING SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK CONNECTOR  .
   1. Check connecting condition of the A/C control panel connector and air mix door actuator LH connector (with left/right independent air conditioner) or air mix door actuator connector (without left/right independent air conditioner).
   2. Turn the ignition switch to ON.
   3. Read the DTC of [Air Conditioner] using the Subaru Select Monitor. Ref. to AIR CONDITIONER (DIAGNOSTICS) (EXCEPT FOR HEV)>DIAGNOSTIC TROUBLE CODE (DTC) .

      Is DTC B1440 displayed? (Current malfunction)

      Yes:  Go to  2.

      No:  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.
2. CHECK ACTUATOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the air mix door actuator LH (with left/right independent air conditioning function) or air mix door actuator (without left/right independent air conditioning function).
   3. For model with left/right independent air conditioner, short No. 2 and No. 1 of connector i174. For model without left/right independent air conditioner, short No. 2 and No. 3 of connector i175.
   4. Turn the ignition switch to ON.
   5. Read the DTC of [Air Conditioner] using the Subaru Select Monitor. Ref. to AIR CONDITIONER (DIAGNOSTICS) (EXCEPT FOR HEV)>DIAGNOSTIC TROUBLE CODE (DTC) .

      Is DTC B1442 displayed? (Current malfunction)

      Yes:  Replace the air mix door actuator LH (with left/right independent air conditioning function) or air mix door actuator (without left/right independent air conditioning function). Ref. to AIR CONDITIONER (EXCEPT FOR HEV)>AIR MIX DOOR ACTUATOR .

      No:  Go to  3.

3. CHECK HARNESS  .
   1. Turn the ignition switch to OFF.
   2. Restore the temporary shorted lines made in step 2.
   3. Turn the ignition switch to ON.
   4. Using a tester, measure the voltage between terminals in the air mix door actuator LH connector (with left/right independent air conditioning function) or air mix door actuator connector (without left/right independent air conditioning function).

      Connector and terminal 

      With left/right independent air conditioning function

      (1174) No. 3 (+) - (i174) No. 1 (-):

      Without left/right independent air conditioning function

      (1175) No. 1 (+) - (i175) No. 3 (-):

      Is the voltage 4.5 - 5.5 V?

      Yes:  Go to  4.

      No:  Repair or replace the open circuit of harness.

4. CHECK HARNESS (OPEN CIRCUIT)  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from the A/C control panel.
   3. Using a tester, check the continuity between A/C control panel connector and air mix door actuator LH (with left/right independent air conditioning function) or air mix door actuator connector (without left/right independent air conditioning function) terminals.

      Connector and terminal 

      With left/right independent air conditioning function

      (i174) No. 3 - (i88) No. 16:

      (i174) No. 1 - (i88) No. 30:

      (1174) No. 2 - (i88) No. 35:

      Without left/right independent air conditioning function

      (1175) No. 1 - (i88) No. 16:

      (i175) No. 3 - (i88) No. 30:

      (i175) No. 2 - (i88) No. 35:

      Is there continuity?

      Yes:  Replace the A/C control panel. Ref. to AIR CONDITIONER (EXCEPT FOR HEV)>CONTROL PANEL .

      No:  Repair or replace the open circuit of harness.