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 BLOWER CONTROL dial to OFF, the TEMPERATURE CONTROL dial to Max Cool, the VENT 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.

*: With mirror defogger

4.
The recirculation indicator blinks two times, then the self-diagnostic function begins.

NOTE:
The blower motor will run at various speeds when in the self-diagnostic mode.
If there is any problem in the system, the recirculation indicator blinks Diagnostic Trouble Code (DTC) number 1 through 13.
If there are multiple DTCs, the recirculation indicator blinks each DTC in sequence from the lowest DTC number to the highest.
If there are no problems detected, the indicator will not blink.

Example of DTC Indication Pattern (DTC 3)

Example of DTCs Indication Pattern (DTC 2 and 4)
DTC (Recirculation Indicator blinks)
Detection Item
1
An open in the air mix control motor circuit
2
A short in the air mix control motor circuit
3
A problem in the air mix control motor circuit, linkage, door, or motor
4
An open in the mode control motor circuit
5
A short in the mode control motor circuit
6
A problem in the mode control motor circuit, linkage, door, or motor
7
An open in the recirculation control motor circuit
8
A short in the recirculation control motor circuit
9
A problem in the recirculation control motor circuit, linkage, door, or motor
10
A problem in the blower motor circuit
11
HVAC control unit internal error
12
An open in the evaporator temperature sensor circuit
13
A short in the evaporator temperature sensor circuit

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 for History DTCs
The HVAC control unit can record history DTCs. To read the history DTCs, do the following:

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

2.
Set the BLOWER CONTROL dial to OFF.

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

4.
The VENT indicator blinks two times, then the history DTCs are indicated.

NOTE:
If there is any problem in the system, the VENT indicator blinks Diagnostic Trouble Code (DTC) number 1 through 13.
If there are multiple DTCs, the VENT indicator blinks each DTC in sequence from the lowest DTC number to the highest.
If there are no problems detected, the indicator will not blink.

Example of DTC Indication Pattern (DTC 3)

Example of DTCs Indication Pattern (DTC 2 and 4)
DTC (Ventilation Indicator blinks)
Detection Item
1
An open in the air mix control motor circuit
2
A short in the air mix control motor circuit
3
A problem in the air mix control motor circuit, linkage, door, or motor
4
An open in the mode control motor circuit
5
A short in the mode control motor circuit
6
A problem in the mode control motor circuit, linkage, door, or motor
7
An open in the recirculation control motor circuit
8
A short in the recirculation control motor circuit
9
A problem in the recirculation control motor circuit, linkage, door, or motor
10
A problem in the blower motor circuit
11
HVAC control unit internal error
12
An open in the evaporator temperature sensor circuit
13
A short in the evaporator temperature sensor circuit

How to Cancel Reading History DTCs
5.
Turn the ignition switch to LOCK (0), to cancel the read history DTCs. After completing the repair work, clear the DTCs.
How to Clear History DTCs
1.
Turn the ignition switch to LOCK (0).

2.
Set the BLOWER CONTROL dial to OFF, the TEMPERATURE CONTROL dial to Max Cool.

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 defrost indicator starts to blink, release the buttons. The indicator will blink 5 times then stop.

5.
Do the How to Check for History DTCs to verify DTCs have been cleared.