DTC B1431: In-Vehicle (Post Evaporator) Temperature Sensor Circuit Short-Circuit

DTC detecting condition: 

In-vehicle sensor circuit is shorted.

Trouble symptom: 

In-vehicle air temperature is falsely recognized as 25°C (77°F), and the compartment temperature is adjusted.

Wiring diagram: 

Air conditioning system Ref. to WIRING SYSTEM (CROSSTREK MODEL (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 and in-vehicle sensor connector.
   2. Turn the ignition switch to ON.
   3. Read the DTC of [Air Conditioner] using the Subaru Select Monitor. Ref. to AIR CONDITIONER (DIAGNOSTICS) (HEV)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC B1431 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 IN-VEHICLE SENSOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the in-vehicle sensor. Ref. to AIR CONDITIONER (HEV)>IN-VEHICLE SENSOR (AUTO A/C MODEL) .
   3. Turn the ignition switch to ON.
   4. Read the DTC of [Air Conditioner] using the Subaru Select Monitor. Ref. to AIR CONDITIONER (DIAGNOSTICS) (HEV)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC B1430 displayed? (Current malfunction)

   Yes  : Replace the in-vehicle sensor. Ref. to AIR CONDITIONER (HEV)>IN-VEHICLE SENSOR (AUTO A/C MODEL) .

   No  : Go to  3.

3. CHECK HARNESS  .

   Using a tester, measure the voltage between terminals in in-vehicle sensor connector.

   Connector & terminal 

   (i173) No. 1 (+) - (i173) No. 2 (-):

   Is the voltage 4.5 - 5.5 V?

   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  : Go to  4.

4. CHECK HARNESS (SHORTED BETWEEN LINES)  .
   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 terminals in in-vehicle sensor connector.

      Connector & terminal 

      (i173) No. 1 - (i173) No. 2:

   Is there continuity?

   Yes  : Repair or replace the short circuit of the harness.

   No  : Replace the A/C control panel. Ref. to AIR CONDITIONER (HEV)>CONTROL PANEL .