DTC Troubleshooting: B1231 (09)
DTC B1231 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 09 indicated?

     
YES
     
     
     
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):

Open wire check (TEVA line)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connectors.
Climate control unit 32P connector
Evaporator temperature sensor 2P connector

?3.
Check for continuity between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
Climate control unit 32P connector: disconnected
Evaporator temperature sensor 2P connector: disconnected
Test point 1
Climate control unit 32P connector No. 18
Test point 2
Evaporator temperature sensor 2P connector No. 2


Is there continuity?

     
YES
     
     
     
The TEVA wire is not open. Go to step 3.
     
NO
     
     
     
Repair an open in the wire between the climate control unit and the evaporator temperature sensor.?
3.
Open wire check (SENSOR COM line):

Open wire check (SENSOR COM line)
?1.
Check for continuity between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
Climate control unit 32P connector: disconnected
Evaporator temperature sensor 2P connector: disconnected
Test point 1
Climate control unit 32P connector No. 30
Test point 2
Evaporator temperature sensor 2P connector No. 1


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 evaporator temperature sensor.?
4.
Shorted wire check (TEVA line to power):

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 32P connector: disconnected
Evaporator temperature sensor 2P connector: disconnected
Test point 1
Climate control unit 32P connector No. 18
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 evaporator temperature sensor.?
     
NO
     
     
     
The TEVA wire is not shorted. Go to step 5.
5.
Evaporator temperature sensor check:

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
     
     
     
     
NO