How to Use the HVAC Control Unit Self-Diagnostic Function Without the HDS

The HVAC control unit has a self-diagnostic function for heating, ventilation, and air conditioning system. To run the self-diagnostic function, do the following:

1. Turn the ignition switch to LOCK (0), and then back to ON (II).
2. Set the FAN speed to ON with the ON/OFF button, and the FRONT TEMPERATURE CONTROL dial to Max Cool.
3. Set the FAN speed to OFF with the ON/OFF button, and the FRONT MODE CONTROL button to VENT.
4. Press and hold the RECIRCULATION CONTROL button, then within 10 seconds press and release the REAR WINDOW DEFOGGER/MIRROR DEFOGGER button five times. Release the RECIRCULATION CONTROL button; the recirculation indicator blinks two times, then the self-diagnosis begins.
   NOTE:

   • The self-diagnostic test could take up to two minutes to run.
   • The blower motor should run at various speeds regardless of what the panel is displaying.
   • If there is any problem in the system after the self-diagnostic function is finished, the recirculation indicator blinks Diagnostic Trouble Code (DTC) 1 through 8. In the case of multiple problems, the recirculation indicator blinks in order with the lowest number DTC repeatedly.
   • If no DTCs are found, the indicator does not blink.
     Fig 1: Identifying HVAC Control Unit Buttons

     Courtesy of AMERICAN HONDA MOTOR CO., INC.

   Example of DTC Indication Pattern (DTC 3) 

   Fig 2: DTC Indication Pattern (DTC 3)

   Courtesy of AMERICAN HONDA MOTOR CO., INC.

   Example of DTC Indication Pattern (DTC 2 and 4) 

   Fig 3: DTC Indication Pattern (DTC 2 And 4)

   Courtesy of AMERICAN HONDA MOTOR CO., INC.
   DTC REFERENCE CHART
   
   

   DTC (Recirculation Indicator Blinks)	Detection Item
   1	A problem in the blower motor circuit (front)
   2	An open in the air mix control motor circuit (front)
   	A short in the air mix control motor circuit (front) (see DTC B1234 OR DTC INDICATOR 2: A SHORT IN THE AIR MIX CONTROL MOTOR CIRCUIT (FRONT)  )
   	A problem in the air mix control motor circuit, linkage, door, or motor (front) (see DTC B1235 OR DTC INDICATOR 2: A PROBLEM IN THE AIR MIX CONTROL MOTOR CIRCUIT, LINKAGE, DOOR, OR MOTOR (FRONT)  )
   3	An open or short in the mode control motor circuit (front)
   	A problem in the mode control motor circuit, linkage, door, or motor (front) (see DTC B1240 OR DTC INDICATOR 3: A PROBLEM IN THE MODE CONTROL MOTOR CIRCUIT, LINKAGE, DOOR, OR MOTOR (FRONT)  )
   4	An open in the evaporator temperature sensor circuit
   	A short in the evaporator temperature sensor circuit (see DTC B1232 OR DTC INDICATOR 4: A SHORT IN THE EVAPORATOR TEMPERATURE SENSOR CIRCUIT  )
   5	An open in the A/C pressure sensor circuit
   	A short in the A/C pressure sensor circuit (see DTC B2980 OR DTC INDICATOR 5: A SHORT IN THE A/C PRESSURE SENSOR CIRCUIT  )
   8	An open or short in the recirculation control motor circuit
   	A problem in the recirculation control linkage, door, or motor circuit (see DTC B2983 OR DTC INDICATOR 8: A PROBLEM IN THE RECIRCULATION CONTROL MOTOR CIRCUIT, LINKAGE, DOOR, OR MOTOR  )

   Canceling the Self-Diagnostic Function 

5. Turn the ignition switch to LOCK (0), to cancel the self-diagnostic function. After completing the repair work, run the self-diagnostic function again to make sure that there are no other DTCs.