Electronic Ignition (EI) System

The Electronic Ignition (EI) system consists of the following components and wiring circuits:
^ The Ignition Control (IC) module
^ The ignition coils
^ The Powertrain Control Module (PCM)
^ The 24X Crankshaft Position (CKP) Sensor
^ The 7X CKP sensor
^ The Camshaft Position (CMP) sensor

The EI wiring circuits listed here use the following service common names. Between the IC module and the PCM:
^ Low resolution engine speed signal
^ IC timing control
^ IC timing signal
^ Low reference

Between the 7X CKP sensor and the IC module:
^ CKP sensor (1) signal
^ Low reference

Between the 24X CKP sensor and the PCM:
^ Medium resolution engine speed signal
^ 12-volt reference
^ Low reference

Between the CMP and the PCM:
^ CMP sensor signal
^ Low reference
^ 12-volt reference.

The IC module also receives power and chassis ground through the following circuits:
^ Ignition voltage
^ Ground

Purpose
The EI system is responsible for producing and controlling a high energy secondary spark. This spark is used to ignite the compressed air/fuel mixture at precisely the correct time to provide optimal performance, fuel economy, and control of exhaust emissions.

Operation
In this El system there is one coil for each pair of cylinders. Each pair is at Top Dead Center (TDC) at the same time, and are known as companion cylinders. The cylinder that is at TDC the compression stroke is called the event cylinder. The cylinder that is at TDC of the exhaust stroke is called the waste cylinder. When the coil is triggered, both plugs fire at the same time, completing a series circuit. Because the lower pressure inside the waste cylinder offers very little resistance, the event cylinder uses most of the available voltage producing a very high energy spark. This is known as waste spark ignition.