Ignition System: Description and Operation

Circuit Description
As the crankshaft turns, the engine control module (ECM) receives input signals from the crankshaft and camshaft position sensor. Based on these inputs and other sensor signals, the engine control module (ECM) controls the current through the ignition coil by turning the power transistor (built -in the ECM) on and off.

When current flow through the primary winding is stopped, a high voltage is induced in the secondary winding of the ignition coil. The high voltage is applied to the spark plug.