DTC B1225 (A and AUTO)

DTC B1225 or DTC indicator A and AUTO  : An Open in the In-Car Temperature Sensor Circuit

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 climate control unit.

   - 4. Check for DTCs.

   DTC Description	DTC
   B1225 An open in the in-car temperature sensor circuit

   Is DTC B1225 or A and AUTO indicated?

   YES 

   Go to step 2.

   NO 

   Intermittent failure. Check for loose wires or poor connections on the in-car temperature sensor circuit.

2. Open wire check (SENS TR line)

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

   - 2. Disconnect the following connectors.

   Climate control unit connector C (12P)

   Humidity/in-car temperature sensor 4P connector

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

   Test condition	Vehicle OFF (LOCK) mode
   	Climate control unit connector C (12P): disconnected
   	Humidity/in-car temperature sensor 4P connector: disconnected
   Test point 1	Climate control unit connector C (12P) No. 8 - Refer to: Climate Control Unit Connector For Inputs and Outputs (2019 2020 2021), or Climate Control Unit Connector For Inputs and Outputs (2016 2017 2018)
   Test point 2	Humidity/in-car temperature sensor 4P connector No. 1

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

   Is there continuity?

   YES 

   The SENS TR wire is not open. Go to step 3.

   NO 

   Repair an open in the wire between the climate control unit and the humidity/in-car temperature sensor.

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

   - 1. Disconnect the following connector.

   Climate control unit connector A (32P)

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

   Test condition	Vehicle OFF (LOCK) mode
   	Climate control unit connector A (32P): disconnected
   	Climate control unit connector C (12P): disconnected
   	Humidity/in-car temperature sensor 4P connector: disconnected
   Test point 1	Climate control unit connector A (32P) No. 18 - Refer to: Climate Control Unit Connector For Inputs and Outputs (2019 2020 2021), or Climate Control Unit Connector For Inputs and Outputs (2016 2017 2018)
   Test point 2	Humidity/in-car temperature sensor 4P connector No. 2

   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 climate control unit and the humidity/in-car temperature sensor.

4. Shorted wire check (SENS TR 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 A (32P): disconnected
   	Climate control unit connector C (12P): disconnected
   	Humidity/in-car temperature sensor 4P connector: disconnected
   Test point 1	Climate control unit connector C (12P) No. 8 - Refer to: Climate Control Unit Connector For Inputs and Outputs (2019 2020 2021), or Climate Control Unit Connector For Inputs and Outputs (2016 2017 2018)
   Test point 2	Body ground

   Is there any voltage?

   YES 

   Repair a short to power in the wire between the climate control unit and the humidity/in-car temperature sensor.

   NO 

   The SENS TR wire is not shorted. Go to step 5.

5. In-car temperature sensor check

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

   - 2. Test the in-car temperature sensor.

   Is the in-car temperature sensor OK?

   YES 

   Replace the climate control unit .

   NO 

   Replace the humidity/in-car temperature sensor .