The low voltage side of the ignition system is known as the primary circuit. This includes the battery, the ignition switch, the primary coil winding, an activation system and a switching device. On the other hand, the high voltage side of the system is known as the secondary circuit. In this is the package of coils and spark plugs. Many ignition components are not used in many engines today. Instead, they use only one package of coils which is above the spark plug. This package transforms the low voltage of the primary circuit into a high secondary voltage which is necessary to activate the plugs.
The coil pack circuit is controlled by the PCM (Powertrain Control Module) who connects or disconnects this circuit and thus activates or deactivates the coil. The PCM establishes diagnostic code P0358 OBD2 when it detects inconsistencies in the electrical circuit of the ignition coil. This code refers to ignition coil number 8.