Computer Controlled Coil Ignition: Notes
The Computer Controlled Coil Ignition (C3 I) system, used on 3.8L, eliminates the need for a mechanical distributor. The C3 I ignition system consists of an ignition coil pack (3 coils), ignition control module, Hall Effect camshaft and crankshaft sensors, necessary wiring, and the ignition control and fuel metering portion of the PCM.
In the C3 I system, each cylinder is paired with the cylinder that is opposite it in the firing order. Cylinder No. 1 is paired with No. 4, No. 2 with No. 5, and No. 3 with No. 6. Spark occurs simultaneously in the cylinder approaching the compression stroke and in the cylinder approaching the exhaust stroke. The cylinder on the exhaust stroke requires less voltage for the spark plug to fire. This leaves the bulk of the available voltage to fire the spark plug for the cylinder on the compression stroke. The process is repeated when the cylinders reverse roles. Each cylinder pair is fired by its own ignition coil.
Input signals from the Hall Effect (3X and 18X) dual crankshaft sensor and Hall Effect camshaft sensor are used by the ignition control module to determine when to trigger the appropriate coil pack. Ignition control module passes on camshaft sync-pulse signal to the PCM to initialize sequential fuel injector timing.