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

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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:

Turn the ignition switch to LOCK (0), and then back to ON (II).
Set the FAN speed to ON with the ON/OFF button, and the FRONT TEMPERATURE CONTROL dial to Max Cool.
Set the FAN speed to OFF with the ON/OFF button, and the FRONT MODE CONTROL button to VENT.

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)
3	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
4	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
5	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
8	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

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.