D21 Hardbody 2WD L4-2389cc 2.4L SOHC MFI (KA24E) (1990)
Power Transistor: Description and Operation
Fig. 34 Power Transistor and Ignition Coil
The power transistor, located on the coil bracket on the left fender apron, 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.