The General Motors full automatic temperature control (FATC) air conditioning controller contains a self-diagnosis function to aid in finding any problem with the system. If the ATC detects some errors it will blink the temperature display screen for 5 seconds when the ignition switch is ON.
To enter the diagnostic mode, perform the following procedure.
- Turn ON the ignition.
- Set the temperature control to 26°C (79°F).
- Within 3 seconds, push the AUTO and the OFF switches simultaneously, more that 3 times.
- Inspect the diagnostic trouble code (DTC) in the temperature indicator screen blinks. If there are no DTCs set the screen will display 00.
- When the FATC controller indicates a DTC, proceed to the table for the DTC.
- Push the OFF switch to return the control to its normal function.
Fault Safety Function
ATC air conditioner not only performs self-diagnosis but also has safety function against faults. If there is open or short in the sensors or potentiometer of temperature door some specific value will be substitute.
Item | DTC | Fault Safety Function |
|---|---|---|
In-Car Sensor | 1 | 25°C will be substituted as temperature of inside of vehicle |
Ambient Temperature Sensor | 2 | 25°C will be substituted as ambient temperature |
Coolant Temperature Sensor | 3 | Sensor ON 100°C will be substituted as coolant temperature |
Sun Sensor | 5 | Zero will be substituted as sun load |
If no DTCs are present, refer to Symptoms - HVAC Systems - Automatic .
