P0351: Ignition Coil A Primary Control Circuit/Open
Do not keep driving
Expect a rough engine and lost power. Stop if the warning light is flashing. If plugs have not been changed in a long time, mention it — old plugs cause coil failures rather than merely accompanying them.
What this code means
A fault in coil A, which on almost all engines serves cylinder 1. This is the code that makes the classic swap test worthwhile: move the coil to an adjacent cylinder, clear the code, and see whether the fault follows it. If it does, the coil is proven faulty without buying anything; if it stays put, the fault is in the wiring or the module driver.
A worn spark plug is a genuine cause rather than a coincidence — a widened gap raises the voltage the coil must produce, and coils fail from being asked to work beyond their design. Replacing a coil without replacing the plug that killed it invites the same failure again.
Likely causes
Start here
- Faulty ignition coil · easy
- Worn or fouled spark plugs · easy
- Corroded or loose connector · easy
- Damaged spark plug wire or boot · easy
Less common
- Open circuit in coil wiring · moderate
- Oil or coolant contamination in plug well · moderate
Rare
- Control module driver failure · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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