Stepper Motor Diagnostics

Fault diagnosis on the heater stepper motors falls into two main groups:

• Electrical fault: A diagnostic trouble code (DTC) will be raised and logged in the automatic temperature control (ATC) module memory.
• Mechanical fault: The programmed de-frost light emitting diode (LED) will blink to indicate the automatic temperature control (ATC) module is attempting to carry out a calibration routine.

A calibration routine will be initiated by the automatic temperature control (ATC) module if any of the following occur:

• One or more of the stepper motors is replaced.
• The automatic temperature control (ATC) module is replaced.
• A foreign object enters the system and causes a stepper motor to stall.

Stepper motor related diagnostic trouble code (DTC)s are stored in the automatic temperature control (ATC) module memory and can be retrieved using T4. Refer to Climate Control System information.