Ignition Control Module: Description and Operation

Ignition Coil And Power Transistor:

The power transistor, in-line between the ignition coil and ECM, is the switch that triggers the coil. By calculating various inputs, the ECM controls ignition timing through its control of the power transistor. The ECM considers input from the crank angle sensor, throttle valve switch, coolant temperature sensor, air flow sensor, knock sensor and vehicle speed sensor when calculating ignition timing.