P0351

Universal

Ignition Coil A Primary/Secondary Circuit Malfunction

Definition source: General OBD-II reference catalog
Definition verification: Not independently verified for display.
Time: Varies by diagnosis and vehicle | Diagnostic difficulty: Medium
Medium Severity

The ignition coil helps create the spark that ignites the air-fuel mixture. P0351 means the vehicle detected a fault in the primary or secondary electrical circuit associated with ignition Coil A. Depending on the vehicle, this may cause a misfire, reduced performance, or no noticeable symptoms. The code does not by itself prove the coil needs replacement.

Report an error with this code

⚠️ Before You Begin (Safety First)

If the engine is shaking severely, losing power, or the check-engine light is flashing, stop driving when safe and arrange diagnosis; an active misfire can damage the catalytic converter. Avoid touching ignition components while the engine is running. Have a qualified technician perform tests that require specialized electrical equipment or procedures.

Common Symptoms

  • Engine misfire, rough idle, or shaking if the affected circuit interrupts spark.
  • Hesitation or reduced power, especially when the engine is under load, if spark is inconsistent.
  • Check-engine light; it may flash if the engine is misfiring severely.
  • Hard starting or stalling may occur if the fault significantly disrupts ignition.
  • Reduced fuel economy or increased exhaust emissions may result from incomplete combustion.
  • No obvious symptoms are possible if the fault is intermittent or does not noticeably affect engine operation.

Common Causes

  • An ignition coil fault affecting its primary or secondary circuit.
  • A loose, damaged, corroded, or contaminated coil connector.
  • Damaged wiring or a poor electrical connection in the coil circuit.
  • A problem with the circuit’s power supply or ground.
  • A fault in the engine computer’s coil-control circuit.
  • A related ignition component or secondary-circuit problem that affects coil operation.

Diagnostic Steps

  1. Record the stored codes and any available freeze-frame information before clearing anything; related codes and operating conditions can help narrow the cause.
  2. With the engine off and cool, visually inspect the Coil A connector and nearby wiring for looseness, corrosion, damaged insulation, or signs of heat or moisture.
  3. Check that the connector is seated securely, but do not pull on wires or probe terminals without the correct vehicle-specific information.
  4. If the vehicle’s service information identifies an accessible coil or boot inspection, check for visible damage or contamination; do not handle ignition components with the engine running.
  5. If the engine is running roughly, losing power, or the check-engine light is flashing, avoid further driving and arrange professional diagnosis.
  6. Do not replace the coil based only on this code; use model-, year-, and engine-specific service information or seek qualified electrical testing.

When to Call a Professional

Confirm the code and review related codes and misfire data before replacing parts. Inspect the coil connector and wiring, then use the vehicle-specific wiring diagram to test the circuit and coil as appropriate. Further checks may include verifying power, ground, the control signal, and the coil’s secondary circuit. Follow model-, year-, and engine-specific service information.

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Commonly Asked Questions

Does P0351 mean the ignition coil must be replaced?

No. The code identifies a detected fault in Coil A’s primary or secondary circuit. The coil, its connector or wiring, its power or ground, or the control circuit may need investigation.

Can I drive with P0351?

It depends on how the engine is running. If there is severe shaking, power loss, or a flashing check-engine light, stop driving when safe and arrange diagnosis because a severe misfire can damage the catalytic converter.

Why might there be no noticeable symptoms?

A circuit fault can be intermittent or may not disrupt ignition enough to cause obvious changes. A stored code still warrants diagnosis, particularly if it returns.

What should be checked before replacing parts?

Check related codes and misfire information, inspect the coil connector and wiring, and test the circuit using the correct vehicle-specific wiring diagram and service procedures.

Browse Available Code Guides

Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.