Ignition Control Module: Description and Operation

EDIS Module:

PURPOSE
The Electronic Distributorless Ignition System (EDIS) module's primary function is to deliver full energy spark at a crank angle targeted by the Electronic Control Assembly (ECA) module and to provide the ECA with crankshaft position information.

CONSTRUCTION
The EDIS ignition module is a twelve pin custom microprocessor-based thick film module. Even though each engine is very different in size and structure, EDIS modules for each engine are very similar. With the exception of some pin assignments, basic operation of the EDIS systems for the different engines is identical.

OPERATION
The EDIS module receives input from the Variable Reluctance Sensor (VRS) style Crankshaft Position Sensor (CKP) in order to identify the passing of the missing tooth on the VRS trigger wheel. The module is said to be "synchronized" when the missing tooth is found. Synchronization is essential to the EDIS module in order to track the angular position of the crankshaft relative to a fixed reference and when it should fire the proper coil.

Profile Ignition Pickup (PIP) output is synthesized by the EDIS module using input from the VRS signal. The PIP signal generated by the EDIS module indicates engine speed and crankshaft position to the ECA. The PIP signal is used by the ECA so that it can enable fuel and spark functions and generate a Spark Angle Word (SAW) signal.


The SAW signal provides spark targeting information to the EDIS module. By decoding the SAW signal and using the information it receives from the VRS, the EDIS module turns the coils "ON" and "OFF" at correct times and in proper sequence. The EDIS system operates at a high data rate so it can fire sparks more accurately.