A method of operating a plug-in hybrid electric vehicle is provided including the steps of: A) determining whether the plug-in hybrid electric vehicle is receiving power from an external power source; B) disabling the operation of the plug-in hybrid electric vehicle and executing a thermal program if the plug-in hybrid electric vehicle is receiving power from the external power source, wherein the thermal program includes charging a high voltage battery and monitoring the state of charge of the high voltage battery; C) determining if the plug-in hybrid electric vehicle continues to receive power from the external power source; and D) enabling operation of the plug-in hybrid electric vehicle if the plug-in hybrid electric vehicle is no longer receiving power from the external power source.