B1231

DTC Troubleshooting: B1231 (G and AUTO)

DTC B1231 or DTC indicator G and AUTO:

An Open in the Evaporator Temperature Sensor Circuit

1. Clear the DTCs with the HDS.

2. Turn the ignition switch to LOCK (0) and then back to ON (II).

3. Do the self-diagnostic function with the HDS or the climate control unit.

4. Check for DTCs.

Is DTC B1231 or G and AUTO indicated?

YES -

Go to step 5.

NO -

Intermittent failure, check for loose wires or poor connections in the evaporator temperature sensor circuit.

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

6. Remove the evaporator temperature sensor Service and Repair, and test it Testing and Inspection.

Is the evaporator temperature sensor OK?

YES -

With the evaporator temperature sensor disconnected, go to step 7.

NO -

Replace the evaporator temperature sensor Service and Repair.

7. Disconnect the climate control unit 36P connector.

8. Check for continuity between climate control unit 36P connector terminal No. 23 and evaporator temperature sensor 2P connector terminal No. 1.





Is there continuity?

YES -

Go to step 9.

NO -

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

9. Check for continuity between climate control unit 36P connector terminal No. 1 and evaporator temperature sensor 2P connector terminal No. 2.





Is there continuity?

YES -

Check for loose wires or poor connections at the climate control unit 36P connector and at the evaporator temperature sensor 2P connector. If the connections are good, substitute a known-good climate control unit, 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.