Procedure for Automatic Temp Control (ATC) equipped vehicles: With the engine ON and the vehicle stopped set the temp to 75*F. Next hold down the Floor, Mix and Defrost buttons until the ATC display begins to flash. While the display is flashing, the system will run it's tests and calibrations.
When the display stops flashing, the tests and calibrations are complete.
The ATC display can only display one error code at a time. Any stored codes can be scrolled through by pressing the Panel mode button once for each code. DO NOT press any other button or you will have to start the test over. Note the codes and refer to the list below to determine what system is malfunctioning.
Procedure for Manual Temp Control (MTC) equipped vehicles: Set the FAN SPEED knob to anything except OFF.
Set the TEMPERATURE knob all the way into the COLD position.
The MODE knob must be in DEFROST.
The A/C button can be on or off.
Press and hold the EBL (electric back light, a.k.a rear windshield defrost) button until AC00 appears in the odometer display. You will hear a chime and the A/C light will blink.
Release the EBL button and wait for the A/C light to stop blinking.
Codes will display in the odometer in the form ACxx where xx is the actual trouble code. Only one code can be displayed at a time, to scroll through the codes press the A/C button. You will hear a beep every time the button is pushed. When all codes have been displayed, the odometer will return to normal. DO NOT push other buttons or turn any knobs while doing this or the test will be aborted and you will have to start over.
List of Climate Control DTCs:
23: Blend door actuator feedback failure (bad servo)
24: Mode door actuator feedback failure (bad servo)