Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Computer Controlled Coil Ignition (C(3)I): Notes
The Computer Controlled Coil Ignition (C(3)I) system, used on 3.8L, eliminates the need for a mechanical distributor. The C(3)I ignition system consists of a coil pack (3 coils), ignition module, camshaft and crankshaft sensors, wiring harness and the Electronic Spark Timing (EST) portion of the PCM.
In the C(3)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 from the Hall Effect 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 PCM to initialize sequential fuel injector timing.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.