What Does P0358 Mean?
The ECM has detected a primary or secondary circuit malfunction in ignition coil H, serving cylinder #8 on V8 engines. This is the last cylinder in the firing order for most V8 configurations, and the ECM has identified that the coil driver is not operating correctly due to an open, short, or resistance issue in the coil or its wiring. The engine will have a persistent misfire on this cylinder.
Common Causes
40%
Failed ignition coil H due to internal winding breakdown or cracked epoxy insulation from heat cycling
25%
Wiring fault in the coil H trigger or power circuit, often heat-damaged near the rear exhaust manifold on V8 applications
20%
Worn spark plug on cylinder 8 with excessive gap or electrode erosion demanding excessive coil output
15%
ECM coil driver transistor failure for the cylinder 8 ignition output channel
Diagnostic Steps
1
Perform a coil swap test: exchange coil H with a known-good coil from another cylinder, clear codes, and run to see if the fault follows the coil.
2
Measure primary and secondary resistance of coil H and compare to specification and to the other coils. All eight coils should read within 10% of each other.
3
Inspect the cylinder 8 spark plug well for oil or coolant intrusion. On many V8 engines, the rear cylinders have more valve cover gasket leak issues due to heat.
4
Check coil H connector pins for damage, push-back, or corrosion. Verify proper terminal tension by gently tugging on each wire at the connector.
5
If the coil and wiring check good, verify the ECM driver signal for cylinder 8 and check ECM power and ground integrity.
Estimated Repair Cost
$60 - $350
Parts + labor, varies by vehicle and location
The ECM has detected a primary or secondary circuit malfunction in ignition coil H, serving cylinder #8 on V8 engines. This is the last cylinder in the firing order for most V8 configurations, and the ECM has identified that the coil driver is not operating correctly due to an open, short, or resist...
The most common cause of P0358 (Ignition Coil H Primary/Secondary Circuit Malfunction) is: Failed ignition coil H due to internal winding breakdown or cracked epoxy insulation from heat cycling
Typical repair costs for P0358 range from $60 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Cylinder 8 misfire reduces available engine power and creates exhaust imbalance. Continued driving risks catalytic converter overheating from unburned fuel on the affected bank.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0358 to identify the root cause.
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Quick Info
Category
Powertrain
System
Ignition System
Difficulty
Type
Generic (SAE)
Recommended Tools
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