Theory Of Operation
WARNING: This page is about a different car, the 2014 Fiat 500c and 2014 Fiat 500. However, it is still accessible from the selected car via links, so may be relevant.
The primary winding of each coil-on-plug Ignition Coil is supplied power via the Fused Automatic Shut Down (ASD) Relay Output circuit. The Powertrain Control Module (PCM) completes the circuit to ground internally (low side driver) allowing the energy that is stored in the magnetic field of the primary coil to be transferred to the spark plug via the secondary coil. The PCM determines spark timing by monitoring engine operating parameters via various sensors and then calculating the appropriate moment to initiate the spark event. The PCM manages spark advance depending on engine RPM, manifold absolute pressure, engine coolant and oil temperature.