Ignition Coils
WARNING: This page is about a different car, the 2016 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.
Each ignition coil contains a solid state driver module as its primary element. The engine ECM (ECM) signals the coil driver to initiate a firing event by applying ignition control circuit voltage for the appropriate amount of time otherwise known as dwell. When the voltage is removed the coil fires the spark plug.