Ignition Coils
WARNING: This page is about a different car, the 2016 GMC Acadia, 2016 Chevrolet Traverse, and 2016 Buick Enclave. 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.