Reading and Clearing Diagnostic Trouble Codes

Self Test System



The control head has a self test feature that aids in locating trouble in the EATC system. To get reliable results the following procedure must be followed. Turn On the ignition and set the control head to 90, OFF. Wait 40 seconds. If the vacuum fluorescent display (VFD) begins to flash, then there is a malfunction in the blend actuator wiring, the actuator itself or the control head. If the light emitting diode (LED) begins to flash then there is a malfunction in one or more of the other actuators' wiring, the actuator (mode, PAN/DEF, or FA/REC) or the control assembly. If no flashing occurs, set the control assembly to 60, DEF. Wait 40 seconds, look for a flashing VFD. or LED. If no flashing occurs, then no malfunctions in the actuator drive or feedback circuits have been detected. Whether or not flashing has occurred, the self test mode should now be entered for further diagnostic information. To ensure accurate self test results the above procedure must be followed before entering the self test mode.

To enter the self test mode push the OFF and DEFROST mode buttons simultaneously. Within two seconds, push the AUTO mode button. If an 88 is displayed, no malfunctions have been detected by the control assembly. Refer to. Diagnosis in this Section. If a control assembly detectable malfunction has occurred the appropriate error code will be displayed. Refer to Self Test-Error Code. The error code sequence will continue until the cooler button is pushed. When the cooler button is pushed the system will revert to the AUTO mode at a temperature setting one less than the setting before entering the self test mode. Always exit the self test mode by pushing the cooler button before turning Off the ignition. This procedure will ensure the proper resetting of the control assembly when the Ignition is turned On.