How To Troubleshoot The Heating and A/C Systems

Control System DTCs

How to Troubleshoot the Heating and A/C Systems

How to Use the Self-Diagnostic Function

The HVAC control unit has a self-diagnostic function for the 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 control dial to OFF, temperature control dial to Max Cool, the VENTILATION button to ON.

3. Press and hold the RECIRCULATION button, then within 10 seconds press and release the REAR WINDOW DEFOGGER/MIRROR DEFOGGER* button five times. Release the RECIRCULATION button.

*: With mirror defogger

4. The recirculation indicator turns on for 2 seconds, then the self-diagnostic function begins.

NOTE:
* The blower motor will run at various speeds when in the self-diagnostic mode.
* Once the self-diagnostic function is finished, the recirculation indicator blinks, and the number of blinks indicates the Diagnostic Trouble Code (DTC) number. If there are multiple DTCs, the indicator blinks each DTC in sequence from the lowest DTC number to the highest.
* The indicator pauses 3 seconds, then repeats the DTC blink sequence.
* If no DTCs are found, the indicator will not blink.
* When the problem is repaired, DTCs will automatically clear.





Example of DTC Indication Pattern (DTC 3)





Example of DTCs Indication Pattern (DTC 2 and 4)









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.

How to check the past DTC's

The HVAC control unit can record DTCs of the past trouble. How to read the past DTC is as follows.

1. Turn the ignition switch to LOCK (0).

2. Set the fan control dial to OFF, temperature control dial to Max Cool, the VENTILATION button to ON.

3. Press and hold both the RECIRCULATION and the VENTILATION buttons, and turn the ignition switch ON (II).

4. The ventilation indicator turns on for 2 seconds, then the past trouble is indicated.

NOTE:
* In the case of multiple problems, the ventilation indicator will blink the lowest number DTC first.
* If no DTCs are found, the indicator will only blink two times.





Example of DTC Indication Pattern (DTC 3)





Example of DTCs Indication Pattern (DTC 2 and 4)









Canceling the read past DTC's

5. Turn the ignition switch to LOCK (0), to cancel the read past DTC's. After completing the repair work, clear the DTCs.

How to clear the past DTC's.

1. Turn the ignition switch to LOCK (0).

2. Set the fan control dial to OFF, temperature control dial to Max Cool, the VENTILATION button to ON.

3. Press and hold both the RECIRCULATION and WINDSHIELD DEFROSTER buttons, then turn the ignition switch to ON (II).

4. After about 5 seconds the windshield defroster indicator starts to blink, release the buttons. The indicator will blink 5 times then stop.

5. Do the display DTC function to verify DTC's have been cleared.