Climate Control
DTC B1231 or DTC indicator G: An Open in the Evaporator Temperature Sensor Circuit1. Clear the DTC with the HDS.
2. Operate the climate control system in several modes.
3. Check for DTCs using the HDS or self-diagnostic.
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 OFF.
5. Remove the evaporator temperature sensor and test it.
Is the evaporator temperature sensor OK?
YES - Go to step 6.
NO - Replace the evaporator temperature sensor.
6. Disconnect the climate control unit 30P connector.
7. Check for continuity between the climate control unit 30P connector No. 7 terminal and the evaporator temperature sensor 2P connector No. 2 terminal.
Is there continuity?
YES - Go to step 8.
NO - Repair open in the wire between the climate control unit and the evaporator temperature sensor.
8. Check for continuity between the climate control unit 30P connector No. 22 terminal and the evaporator temperature sensor 2P connector No. 1 terminal.
Is there continuity?
YES - Check for loose wires or poor connections at the climate control unit 30P 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.
NO - Repair open in the wire between the climate control unit and the evaporator temperature sensor.