Ignition Control Module: Description and Operation

PURPOSE/OPERATION
The power transistor controls ignition current by interrupting the ignition coil primary ground causing secondary circuit discharge. The engine control module controls ignition timing through the power transistor. The power transistor is a type of switch that allows a very low Voltage (from the engine control module) to control a larger amount of Voltage (negative side of coil). It is actually two power transistors combined into one unit, controlling each circuit of the dual ignition coil. During engine cranking, the ignition timing is fixed at 5°BTDC.