Ignition Coil Primary/Secondary Circuit Malfunction
What does P0350 mean?
The P0350 code means the vehicle's onboard diagnostic system has detected: Ignition Coil Primary/Secondary Circuit Malfunction. This is a moderate severity code.
Common Symptoms
- Engine misfires on one or more cylinders
- Rough idle and vibration
- Check Engine Light illuminated
- Reduced power and acceleration
- Poor fuel economy
Probable Causes (Ranked by Likelihood)
- Faulty ignition coil Very High
- Damaged coil connector or wiring High
- Worn or fouled spark plug causing coil overload High
- PCM ignition coil driver circuit failure Moderate
- Poor engine ground affecting coil circuit Low
Step-by-Step Diagnostic Procedure
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Check for companion misfire codes (P0301-P0312) to identify the affected cylinder
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Measure ignition coil primary resistance -- should be 0.4-2.0 ohms; secondary resistance should be 6,000-15,000 ohms
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Swap the suspect coil with a known-good coil from another cylinder -- if the misfire follows, the coil is bad
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Inspect the coil connector for corrosion, melted plastic, or damaged pins
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Check the spark plug condition -- a worn or fouled plug can cause premature coil failure
Frequently Asked Questions
Can I drive with code P0350?
You can drive short distances. The engine will misfire and run rough. Prolonged driving with a misfiring cylinder can damage the catalytic converter.
Should I replace all ignition coils at once?
It is not strictly necessary, but if one coil has failed and the others are the same age with high mileage, replacing them as a set can prevent future failures and save on repeat labor.
Can a bad spark plug kill an ignition coil?
Yes. A worn or gapped-too-wide spark plug forces the coil to produce higher voltage, which can overheat and burn out the coil prematurely. Always replace spark plugs at recommended intervals.