P0357 moderate

Ignition Coil G Primary/Secondary Circuit Malfunction (Cylinder 7)

The P0357 code means the vehicle's onboard diagnostic system has detected: Ignition Coil G Primary/Secondary Circuit Malfunction (Cylinder 7). This is a moderate severity code.

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Keep driving?: Short distances only
DIY difficulty: easy
Estimated cost: $50 - $350 (parts and labor)

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Common Symptoms

Engine misfire on cylinder 7
Rough idle on V8 engine
Check Engine Light illuminated or flashing
Reduced power
Exhaust has fuel smell

Probable Causes (Ranked by Likelihood)

Faulty ignition coil on cylinder 7 Very High
Worn or fouled spark plug on cylinder 7 High
Damaged coil connector or wiring High
PCM coil driver circuit failure for cylinder 7 Moderate
Spark plug well contamination Low

Step-by-Step Diagnostic Procedure

Swap cylinder 7 ignition coil with another cylinder and clear codes to test
Inspect the spark plug on cylinder 7 for wear, fouling, or damage
Measure coil resistance values and compare to specification
Check coil connector and spark plug well for contamination
Test PCM coil driver signal at the connector

Frequently Asked Questions

Can I drive with code P0357?

You can drive short distances. On V8 engines, losing one cylinder is noticeable but the engine will still run. Repair promptly to prevent catalytic converter damage.

Where is cylinder 7 on a V8 engine?

Cylinder numbering varies by manufacturer. On GM V8s, cylinder 7 is typically on the driver side (bank 2). On Ford V8s, cylinder 7 is on the passenger side. Always check your service manual.

Can a bad coil damage the catalytic converter?

Yes. When a coil fails, unburned fuel from the misfiring cylinder enters the exhaust and can overheat and damage the catalytic converter. A flashing Check Engine Light specifically warns of this condition.