Ignition Control Module: Description and Operation

Ignition Coil And Power Transistor Location:

LOCATION
The power transistor is located on the intake manifold under the ignition coils.

PURPOSE
The power transistor controls ignition current by interrupting the ignition coil primary ground causing secondary circuit discharge.

OPERATION
The ECM controls ignition timing through the power transistor. The power transistor is a type of switch that allows a very low voltage (from the ECM) to control a larger amount of voltage (negative side of coil).

It is actually three power transistors combined into one module, controlling each circuit of the triple ignition coil. During engine cranking, the ignition timing is fixed at 5°BTDC.