Flash: HVAC Diagnostic and System Improvements
This bulletin involves reprogramming the Heating Ventilation Air Conditioning (HVAC) Module with the latest available software.
Some customers may notice one of the following:The Defrost button has to be pressed twice to activate the system.
The Automatic Temperature Control (ATC)/ Manual Temperature Control (MTC) controller may lose its configuration. This condition can happen when the battery is disconnected or becomes low. This condition could also happen if CAN bus communication was lost. The software was changed to monitor the configuration every two secondsand updated it if the last data saved in memory is different from what is being received on the CAN bus to correct this issue (2011 Only).
