DTC B1231 (1)

DTC B1231 or DTC indicator 1  : An Open in the Evaporator Temperature Sensor Circuit (Front)

DTC (AC)

1. Problem verification

   - 1. Clear the DTC with the HDS.

   - 2. Turn the vehicle to the OFF (LOCK) mode then the ON mode.

   - 3. Do the Self-Diagnostic Function with the HDS or the HVAC control unit.

   - 4. Check for DTCs.

   DTC Description	DTC
   B1231 An open in the evaporator temperature sensor circuit (front)

   Is DTC B1231 or 1 indicated?

   YES 

   Go to step 2.

   NO 

   Intermittent failure. Check for loose wires or poor connections on the front evaporator temperature sensor circuit.

2. Open wire check (TEVA line)

   - 1. Turn the vehicle to the OFF (LOCK) mode.

   - 2. Disconnect the following connectors.

   HVAC control unit connector C (12P)

   Front evaporator temperature sensor 2P connector

   - 3. Check for continuity between test points 1 and 2.

   Test condition	Vehicle OFF (LOCK) mode
   	HVAC control unit connector C (12P): disconnected
   	Front evaporator temperature sensor 2P connector: disconnected
   Test point 1	HVAC control unit connector C (12P) No. 11
   Test point 2	Front evaporator temperature sensor 2P connector No. 2

   Courtesy of HONDA, U.S.A., INC.

   Is there continuity?

   YES 

   The TEVA wire is not open. Go to step 3.

   NO 

   Repair an open in the wire between the HVAC control unit and the front evaporator temperature sensor.

3. Open wire check (SENSOR(COM) line)

   - 1. Disconnect the following connector.

   HVAC control unit connector A (32P)

   - 2. Check for continuity between test points 1 and 2.

   Test condition	Vehicle OFF (LOCK) mode
   	HVAC control unit connector A (32P): disconnected
   	HVAC control unit connector C (12P): disconnected
   	Front evaporator temperature sensor 2P connector: disconnected
   Test point 1	HVAC control unit connector A (32P) No. 18
   Test point 2	Front evaporator temperature sensor 2P connector No. 1

   Courtesy of HONDA, U.S.A., INC.

   Is there continuity?

   YES 

   The SENSOR(COM) wire is OK. Go to step 4.

   NO 

   Repair an open in the wire between the HVAC control unit and the front evaporator temperature sensor.

4. Shorted wire check (TEVA line to power)

   - 1. Turn the vehicle to the ON mode.

   - 2. Measure the voltage between test points 1 and 2.

   Test condition	Vehicle ON mode
   	HVAC control unit connector A (32P): disconnected
   	HVAC control unit connector C (12P): disconnected
   	Front evaporator temperature sensor 2P connector: disconnected
   Test point 1	HVAC control unit connector C (12P) No. 11
   Test point 2	Body ground

   Is there any voltage?

   YES 

   Repair a short to power in the wire between the HVAC control unit and the front evaporator temperature sensor.

   NO 

   The TEVA wires OK. Go to step 5.

5. Front evaporator temperature sensor check

   - 1. Turn the vehicle to the OFF (LOCK) mode.

   - 2. Test the front evaporator temperature sensor.

   Is the front evaporator temperature sensor OK?

   YES 

   Replace the HVAC control unit .

   NO 

   Replace the front evaporator temperature sensor - Refer to: Evaporator Temperature Sensor Removal, Installation, and Test, or Rear Evaporator Temperature Sensor Removal, Installation, and Test .