Ignition Control Module (ICM)

Ignition Control Module:

The Ignition Control Module (ICM) is mounted on the ignition coil and is controlled by the Electronic Control Unit (ECU). Based on information received from various sensors, the ECU calculates the precise ignition timing for all engine operating conditions. As timing is calculated, the ECU provides the ICM with a signal to trigger the ignition coil. This signal is received by the ICM in the form of a 5 volt square wave. As the leading edge of the wave contacts the ignition circuitry in the module, the module charges the coil primary windings. When coil saturation occurs, the module circuitry opens the primary windings to collapse the magnetic field in the windings. This induces a high voltage in the coil secondary windings, which is transferred through to the coil wire, rotor, distributor cap, and plug wire to the spark plug.