Computer Controlled Coil Ignition (C3I): Notes

The Computer Controlled Coil Ignition (C3I) system, used on 3.3L and 3.8L, eliminates the need for a mechanical distributor. The C3I ignition system consists of a coil pack (3 coils), ignition module, camshaft and crankshaft (3.8L) or combination (3.3L) sensor, wiring harness and the Electronic Spark Timing (EST) portion of the Electronic Control Module (ECM).

In the C3I system, each cylinder is paired with the cylinder that is opposite it in the firing order. Cylinder No. 1 is paired with 4, 2 with 5, and 3 with 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 from the Hall Effect combination sensor (3.3L) or cam and crank sensors (3.8L) is used by the ignition module to determine when to trigger the appropriate coil pack. On 3.8L, module passes on camshaft sync-pulse signal to the ECM to initialize sequential fuel injector timing.