DTC B1231 or DTC indicator G and AUTO: An Open in the Evaporator Temperature Sensor Circuit (Front)

WARNING: This page is about a different car, the 2013 Acura MDX, 2012 Acura MDX, 2011 Acura MDX, and 2010 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

Clear the DTCs with the HDS.
Turn the ignition switch to LOCK (0) and then back to ON (II).
Do the self-diagnostic function with the HDS (see HOW TO USE THE SELF-DIAGNOSTIC FUNCTION WITH THE HDS ) or the climate control unit (see HOW TO USE THE SELF-DIAGNOSTIC FUNCTION WITHOUT THE HDS ).
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 front evaporator temperature sensor circuit.
Turn the ignition switch to LOCK (0).
Remove the front evaporator temperature sensor (see FRONT EVAPORATOR TEMPERATURE SENSOR REPLACEMENT ), and test it (see FRONT EVAPORATOR TEMPERATURE SENSOR TEST ).
Is the front evaporator temperature sensor OK?

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

NO -Replace the front evaporator temperature sensor (see FRONT EVAPORATOR TEMPERATURE SENSOR REPLACEMENT ).
Disconnect climate control unit connector A (40P).
Check for continuity between climate control unit connector A (40P) terminal No. 24 and front evaporator temperature sensor 2P connector terminal No. 2.

Fig 1: Checking For Continuity Between Climate Control Unit Connector A (40P) Terminal No. 24 And Front Evaporator Temperature Sensor 2P Connector Terminal No. 2
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Go to step 9.

NO -Repair an open in the wire between the climate control unit and the front evaporator temperature sensor.
Check for continuity between climate control unit connector A (40P) terminal No. 8 and front evaporator temperature sensor 2P connector terminal No. 1.

Fig 2: Checking For Continuity Between Climate Control Unit Connector A (40P) Terminal No. 8 And Front Evaporator Temperature Sensor 2P Connector Terminal No. 1
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Check for loose wires or poor connections at climate control unit connector A (40P) and at the front 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 (see CLIMATE CONTROL UNIT REMOVAL/INSTALLATION ).

NO -Repair an open in the wire between the climate control unit and the front evaporator temperature sensor.