In the self-diagnosis system, the ECU transmits any abnormality that occurs in the indicator, sensors, and actuator to the control panel for display to notify the technician. This system is useful for diagnosis because the self-diagnosis results are stored in memory even after the ignition switch is turned off.
Various checks can be performed with the switch operation as shown in the illustration.
Indicators such as switches, temperature setting display and beep activation can be checked. The indicators of the switches and temperature setting display come on four times and go off.
In some models, beep for operation check may sound.
Past or present failures of the sensors can be checked.
When more than one failure is found, pressing the A/C switch will allow all the failures to be viewed one by one.
When the solar sensor is checked indoors, open circuit may be displayed. Expose the solar sensor to incandescent light (fluorescent light is not effective for the check) indoors, or expose to the sunlight outside to check the solar sensor.
In some models, beep to present failure.
A patterned output is transmitted to the actuator to check its performance.
The technician can check for failure of the actuator by transmitting signals from the ECU and activating the airflow dampers, air inlet damper, air mix damper, compressor, etc.
DTC or other data can be checked by connecting the hand-held tester to the DLC3.