Ignition Control Module: Description and Operation

Power Transistor:

The power transistor, located on the R.H. side of the intake plenum, is a low current switch. It allows the signal sent from the ECU (very low current) to activate the primary circuit in the ignition coil (much higher current). This induces high voltage in the secondary windings of the ignition coil, providing spark to the distributor cap and plugs.