P0358
Ignition Coil H Primary/Secondary Circuit Malfunction
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The P0358 code indicates a fault in the primary or secondary circuit of Ignition Coil H, which serves cylinder 8. This code applies exclusively to V8 and larger engines. On most domestic V8 engines (Ford, GM, Chrysler), cylinder 8 is located at the rear of the passenger side (Bank 1), often making it one of the hardest coils to access.
The cylinder 8 position at the rear of the engine, close to the firewall, means it's subjected to significant heat and limited airflow. This can accelerate coil degradation compared to front cylinders. It also means that wiring and connectors in this area are more susceptible to heat damage and may need closer inspection during diagnosis.
As with all ignition coil codes, the recommended approach is the coil swap test followed by targeted replacement. If your V8 has over 80,000 miles and you're seeing its first coil failure, this is a strong signal to replace all eight coils and spark plugs preventively. The other coils are likely near the end of their lifespan too. A complete replacement avoids the frustration and repeated shop visits of coils failing one at a time over the following months, and on V8 engines where rear cylinder access is labor-intensive, it can actually save money in the long run.
Severity
Symptoms
- •Engine misfires on cylinder 8
- •Check Engine light is on (may flash)
- •Rough idle with vibration
- •Noticeable power loss
- •Smell of unburned fuel from exhaust
- •Poor fuel economy
Likely Causes
The cylinder 8 ignition coil has failed due to internal winding breakdown, heat damage, or age-related insulation failure.
The wiring or electrical connector to the cylinder 8 coil is damaged, corroded, or has a loose connection from engine heat and vibration exposure.
A deteriorated spark plug on cylinder 8 has increased secondary resistance beyond acceptable limits, stressing and damaging the coil.
The PCM's internal switching transistor for the cylinder 8 coil driver has failed, preventing proper coil control.
A problem with the ignition power relay, fuse, or shared ground affects the cylinder 8 coil circuit.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Replace the ignition coil for cylinder 8
- Replace the spark plug for cylinder 8
- Repair or replace damaged wiring and connectors
- Swap the coil with another cylinder to confirm the diagnosis
Shop Parts
Videos
Causes and Fixes P0358 Code: Ignition Coil H Primary/Secondary Circuit Malfunction
HVAC Mechanic
P0358 Code Explained - Cylinder 8 Ignition Coil Problem
EZ Automotive