Climate Control Unit

DTC Troubleshooting: B1231 (G)

DTC B1231 or DTC indicator G:

An Open in the Evaporator Temperature Sensor Circuit

NOTE: If DTC B1231 is detected with HDS, it is not necessary to do step 1.

1. Check the sensor input display mode, and select "evaporator temperature sensor" according to the table.

NOTE: This indication by segment lit on digital segments is assigned for 2 failure causes that it is necessary to decide which one is a true cause. If there is a failure in the sensor or motor, a value correspondent to the sensor or motor in the Sensor Input Display Mode is displayed as "Er", which serves to specify which is a true cause.

Is Er indicated?

YES -

Go to step 2

NO -

Go to troubleshooting DTC indicator G HVAC System

2. Clear the DTC with the HDS.

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

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

5. Check for DTCs.

Is DTC B1231 or G indicated?

YES -

Go to step 6.

NO -

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

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

7. Test the evaporator temperature sensor Testing and Inspection.

Is the evaporator temperature sensor OK?

YES -

With the evaporator temperature sensor disconnected, go to step 8.

NO -

Replace the evaporator temperature sensor Service and Repair.

8. Disconnect climate control unit connector A (24P).

9. Check for continuity between climate control unit connector A (24P) terminal No. 13 and evaporator temperature sensor 2P connector terminal No. 2.





Is there continuity?

YES -

Go to step 10.

NO -

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

10. Check for continuity between climate control unit connector A (24P) terminal No. 18 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 connector A (24P) 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.