P0358 moderate

Ignition Coil H Primary/Secondary Circuit Malfunction (Cylinder 8)

The P0358 code means the vehicle's onboard diagnostic system has detected: Ignition Coil H Primary/Secondary Circuit Malfunction (Cylinder 8). 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 8
Rough idle on V8 engine
Check Engine Light illuminated or flashing
Reduced power and acceleration
Poor fuel economy

Probable Causes (Ranked by Likelihood)

Faulty ignition coil on cylinder 8 Very High
Worn or fouled spark plug on cylinder 8 High
Damaged coil connector or wiring High
PCM coil driver circuit failure for cylinder 8 Moderate
Spark plug well moisture or oil contamination Low

Step-by-Step Diagnostic Procedure

Swap cylinder 8 ignition coil with another cylinder and clear codes to test
Inspect the spark plug on cylinder 8 for wear, fouling, or incorrect gap
Measure coil resistance -- primary 0.4-2.0 ohms, secondary 6,000-15,000 ohms
Check the spark plug well for moisture, oil, or debris
Test PCM coil driver signal at the cylinder 8 connector

Frequently Asked Questions

Can I drive with code P0358?

You can drive short distances with a steady Check Engine Light. If flashing, stop driving to prevent catalytic converter damage from unburned fuel.

Is cylinder 8 always the last cylinder on a V8?

Yes. Cylinder 8 is the rearmost cylinder on bank 2 of a V8 engine. On some trucks, this cylinder can be difficult to access due to its proximity to the firewall.

Can extreme cold weather cause ignition coil failure?

Cold weather does not directly cause coil failure, but it puts more demand on the ignition system. A marginal coil that works in warm weather may fail in cold conditions when the engine requires stronger spark for starting.