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.
Ignition System - C3I: Testing
The C(3)I ignition system is an integral part of the engine's computerized engine control system. Refer to 3800 ECM TESTS/CODES article in the COMPUTERIZED ENGINE CONTROLS section for appropriate testing and diagnosis information.
If engine cranks but will not run or if it stalls, CHART A-3 must be used to determine if failure is in the C(3)I ignition system or fuel injection system.
If either Code 41 or Code 42 (E041 or E042 on some models) is set, use appropriate chart for proper diagnosis. If symptom is an engine miss and the C(3)I ignition system is suspected, CHART C-4F must be used.
Use the Manual With the Right Hardware
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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.