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

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

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

   YES 

   The failure is duplicated. Go to step 2.

   NO 

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

2. Open wire check (TEVA line)

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

   -2. Disconnect the following connectors.

   Climate control unit connector B (24P)

   Evaporator temperature sensor 2P connector

   -3. Measure the resistance 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 1.0 Ω or less?

   YES 

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

   NO 

   Repair an open in the TEVA wire.

3. Open wire check (SENS-COM line)

   -1. Measure the resistance 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 1.0 Ω or less?

   YES 

   The SENS-COM wire is OK. Go to step 4.

   NO 

   Repair an open in the SENS-COM wire.

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
   	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	Body ground

   Is there any voltage?

   YES 

   Repair a short to power in the TEVA wire.

   NO 

   The TEVA wire is OK. Go to step 5.

5. Evaporator temperature sensor check

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

   -2. Test the evaporator temperature sensor .

   Is the evaporator temperature sensor OK?

   YES 

   Replace the climate control unit .

   NO 

   Replace the evaporator temperature sensor .