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
  

1.
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.?
2.
Shorted wire check (TEVA line to power):

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):

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


Is resistance value within the range?

     
YES
     
     
     
     
NO
     
     
     
Go to step 4.
4.
Open wire check (TEVA line):

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:


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):

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:


Is there continuity?

     
YES
     
     
     
     
NO
     
     
     
Repair an open in the SENS-COM wire.?