DTC Troubleshooting: B1231 (A-A5), B1231 (09)

DTC B1231 or DTC screen A-A5 or DTC indicator 09  : An open in the evaporator temperature sensor circuit

DTCs (AC)

1. Problem verification

   -1. Clear the DTC with the HDS.

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

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

   -4. Check for DTCs.

   DTC Description	DTC
   B1231 An open in the evaporator temperature sensor circuit

   Is DTC B1231 or Error on the DTC screen A-A5 (climate control panel without display) or 09 (climate control panel with display) indicated?

   YES 

   Go to step 2.

   NO 

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

2. Shorted wire check (TEVA line to power)

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

   -2. Disconnect the following connector.

   Climate control unit connector B (24P)

   -3. Turn the vehicle to the ON mode.

   -4. Measure the voltage between test points 1 and 2.

   Test condition	Vehicle ON mode
   	Climate control unit connector B (24P): disconnected
   Test point 1	Climate control unit connector B (24P) No. 8
   Test point 2	Body ground

   Is there any voltage?

   YES 

   Repair a short to power in the TEVA wire.

   NO 

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

3. Determine possible failure area (climate control unit, others)

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

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

   Test condition	Vehicle OFF (LOCK) mode
   	Climate control unit connector B (24P): disconnected
   Test point 1	Climate control unit connector B (24P) No. 8
   Test point 2	Climate control unit connector B (24P) No. 10

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

   Is resistance value within the range?

   YES 

   Replace the climate control unit .

   NO 

   Go to step 4.

4. Open wire check (TEVA line)

   -1. Disconnect the following connector.

   Evaporator temperature sensor 2P connector

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

   Test condition	Vehicle OFF (LOCK) mode
   	Climate control unit connector B (24P): disconnected
   	Evaporator temperature sensor 2P connector: disconnected
   Test point 1	Climate control unit connector B (24P) No. 8
   Test point 2	Evaporator temperature sensor 2P connector (female terminals) No. 1:

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

   Is there continuity?

   YES 

   The TEVA wire is OK. Go to step 5.

   NO 

   Repair an open in the TEVA wire.

5. Open wire check (SENS-COM line)

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

   Test condition	Vehicle OFF (LOCK) mode
   	Climate control unit connector B (24P): disconnected
   	Evaporator temperature sensor 2P connector: disconnected
   Test point 1	Climate control unit connector B (24P) No. 10
   Test point 2	Evaporator temperature sensor 2P connector (female terminals) No. 2:

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

   Is there continuity?

   YES 

   Replace the evaporator temperature sensor .

   NO 

   Repair an open in the SENS-COM wire.