DTC B1231 or DTC indicator 4: An Open in the Evaporator Temperature Sensor Circuit
- 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 HVAC control unit (see HOW TO USE THE HVAC CONTROL UNIT SELF-DIAGNOSTIC FUNCTION WITHOUT THE HDS ).
- Check for DTCs.
Is DTC B1231 or 4 indicated?
YES -Go to step 5.
NO -Intermittent failure. Check for loose wires or poor connections on the evaporator temperature sensor circuit.
- Turn the ignition switch to LOCK (0).
- Remove the evaporator temperature sensor (see EVAPORATOR TEMPERATURE SENSOR REPLACEMENT
), and test it (see EVAPORATOR TEMPERATURE SENSOR TEST
).
Is the evaporator temperature sensor OK?
YES -With the evaporator temperature sensor disconnected, go to step 7.
NO -Replace the evaporator temperature sensor (see EVAPORATOR TEMPERATURE SENSOR REPLACEMENT ).
- Disconnect the HVAC control unit 28P connector.
- Check for continuity between HVAC control unit 28P connector terminal No. 22 and evaporator temperature sensor 2P connector terminal No. 2.Fig 1: Checking Continuity Between HVAC Control Unit 28P Connector Terminal No. 22 And 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 HVAC control unit and the evaporator temperature sensor.
- Check for continuity between HVAC control unit 28P connector terminal No. 13 and evaporator temperature sensor 2P connector terminal No. 1.Fig 2: Checking Continuity Between HVAC Control Unit 28P Connector Terminal No. 13 And 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 the HVAC control unit 28P connector and at the evaporator temperature sensor 2P connector. If the connections are good, substitute a known-good HVAC control unit, and recheck. If the symptom/indication goes away, replace the original HVAC control unit (see HVAC CONTROL UNIT REMOVAL/INSTALLATION ).
NO -Repair an open in the wire between the HVAC control unit and the evaporator temperature sensor.