B1231
DTC B1231 or DTC indicator G: An Open in the Evaporator Temperature Sensor Circuit1. Clear the DTC by turning the ignition switch OFF, and then ON (II).
2. Operate the climate control system in several modes.
3. Check for DTCs using the self-diagnostic or HDS.
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.
Does the evaporator temperature sensor test OK?
YES - Go to step 6.
NO - Replace the evaporator temperature sensor.
6. Disconnect climate control unit connector A (20P).
7. Check for continuity between the No. 18 terminal of climate control unit connector A (20P) and the No. 1 terminal of the evaporator temperature sensor 2P connector.
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 No. 5 terminal of climate control unit connector A (20P) and the No. 2 terminal of the evaporator temperature sensor 2P connector.
Is there continuity?
YES - Check for loose wire or poor connections at climate control unit connector A (20P) 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.