P0351 moderate

Ignition Coil A Primary/Secondary Circuit Malfunction (Cylinder 1)

The P0351 code means the vehicle's onboard diagnostic system has detected: Ignition Coil A Primary/Secondary Circuit Malfunction (Cylinder 1). This is a moderate severity code.

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Keep driving?: Short distances only
DIY difficulty: easy
Estimated cost: $50 - $300 for coil, spark plug, or wiring repair; $600 - $1,500+ in the rare case the PCM ignition-coil driver has failed and the module must be replaced (parts and labor)

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Common Symptoms

Engine misfire on cylinder 1
Rough idle and vibration
Check Engine Light illuminated or flashing
Reduced power and hesitation
Strong exhaust smell from unburned fuel

Probable Causes (Ranked by Likelihood)

Faulty ignition coil on cylinder 1 Very High
Worn or fouled spark plug on cylinder 1 High
Damaged coil connector or wiring High
PCM coil driver circuit failure for cylinder 1 Moderate
Short in coil-on-plug boot allowing spark leakage Low

Step-by-Step Diagnostic Procedure

Swap cylinder 1 ignition coil with another cylinder -- if the misfire code moves, the coil is bad
Inspect the spark plug on cylinder 1 for wear, fouling, or incorrect gap
Measure coil primary resistance (0.4-2.0 ohms) and secondary resistance (6,000-15,000 ohms)
Check the coil connector for melted plastic, corrosion, or loose pins
Test the PCM coil driver signal at the connector with a noid light or oscilloscope

Common Fixes by Vehicle

What techs usually find when diagnosing P0351 on specific vehicles — tap your vehicle for the fix and the exact part:

2009-2020 Ford F-150/Explorer 3.5L EcoBoost Easy DIY

Ignition coil 1 primary/secondary circuit malfunction. Check the coil connector for backed-out pins or corrosion. Measure coil primary resistance (0.3-1.0 ohm) and secondary resistance (5K-15K ohms). If out of spec, replace with Motorcraft DG-549. If resistance is normal, check the PCM driver circuit and the coil wiring for chafing near the intake manifold.

Labor: 20-30 min

Common fix part Ignition Coil View on Amazon→ Compare fitment at PartsGeek→

2010-2020 Chevrolet Silverado/GMC Sierra 5.3L Easy DIY

Coil 1 circuit fault. Check the ignition coil connector for corrosion or a loose fit. On the 5.3L, engine vibration can loosen coil connectors over time. Measure primary resistance (0.4-1.0 ohm). Replace with ACDelco D513A if out of spec. Also check the coil driver circuit from the ECM. If the connector is corroded, repair the wiring and apply dielectric grease.

Labor: 15-20 min

Common fix part Ignition Coil View on Amazon→ Compare fitment at PartsGeek→

2009-2019 Dodge Ram/Chrysler 5.7L Hemi Easy DIY

Coil 1 primary/secondary circuit malfunction. The Hemi uses individual coil-on-plug ignition. Replace with Mopar 56028394AH. Check the connector for heat damage and corrosion. If the code returns after coil replacement, check the spark plug boot for carbon tracking which causes a short circuit. Also inspect the spark plug for cracking or fouling.

Labor: 15-20 min

Common fix part Ignition Coil View on Amazon→ Compare fitment at PartsGeek→

Frequently Asked Questions

Can I drive with code P0351?

You can drive short distances with a steady Check Engine Light. If the light is flashing, stop driving immediately as this indicates catalytic converter damage is occurring.

Is replacing an ignition coil a DIY repair?

Yes. On most vehicles with coil-on-plug ignition, replacing a coil is a simple DIY task requiring only basic tools. Unbolt the coil, disconnect the connector, and install the new one.

Should I replace the spark plug when replacing the coil?

Yes. A worn spark plug is often the root cause of coil failure. Always replace the spark plug along with the coil to prevent the new coil from being damaged by the old plug.