With Climate Control

DTC Troubleshooting: B1231 (G)

DTC B1231 or DTC indicator G:

An Open in the Evaporator Temperature Sensor Circuit

1. Clear the DTC with the HDS.

2. Operate the climate control system in several modes.

3. Check for DTCs using the HDS or the self-diagnostic function.

Is DTC B1231 or G indicated?

YES -

Go to step 4.

NO -

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

4. Turn the ignition switch to LOCK (0).

5. Remove the evaporator temperature sensor Service and Repair, and test it Evaporator Temperature Sensor Test.

Is the evaporator temperature sensor OK?

YES -

With the evaporator temperature sensor disconnected, go to step 6.

NO -

Replace the evaporator temperature sensor Service and Repair.�

6. Disconnect the climate control unit 30P connector.

7. Check for continuity between climate control unit 30P connector terminal No. 7 and evaporator temperature sensor 2P connector terminal No. 2.





Is there continuity?

YES -

Go to step 8.

NO -

Repair an open in the wire between the climate control unit and the evaporator temperature sensor.�

8. Check for continuity between climate control unit 30P connector terminal No. 22 and evaporator temperature sensor 2P connector terminal No. 1.





Is there continuity?

YES -

Check for loose wires or poor connections at the climate control unit 30P connector and the evaporator temperature sensor 2P connector. If the connections are good, substitute a known-good climate control unit Climate Control Unit Removal/Installation, and recheck. If the symptom/indication goes away, replace the original climate control unit Climate Control Unit Removal/Installation.�

NO -

Repair an open in the wire between the climate control unit and the evaporator temperature sensor.�