My 2014 Verano has cut off on me twice without any warning. Had battery changed and alternator tested, everything fine But my voltage keeps going between 14.1 and 12.5 while driving what could be causing this?

Hello, if your voltage is truly fluctuating that much, then you have an alternator or charging system problem. The alternator and wiring harness / connector should be closely checked. 12.5 is basically an inoperative alternator. Your battery reference voltage when charged should be 12.5 or so.