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

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

Problem verification:

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.?

Shorted wire check (T-EVA line to power):

Shorted wire check (T-EVA 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
Test condition	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 T-EVA wire.?


	NO

The T-EVA wire is not shorted. Go to step 3.

Determine possible failure area (climate control unit, others):

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
Test condition	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

Is resistance value within the range?


	YES

Replace the climate control unit.?


	NO

Go to step 4.

Open wire check (T-EVA line):

Open wire check (T-EVA 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 No. 1

Is there continuity?


	YES

The T-EVA wire is OK. Go to step 5.


	NO

Repair an open in the T-EVA wire.?

Open wire check (SENS COM-H line):

Open wire check (SENS COM-H 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 No. 2

Is there continuity?


	YES

Replace the evaporator temperature sensor.?


	NO

Repair an open in the SENS COM-H wire.?