P0358: Ignition Coil H Primary/Secondary Circuit Malfunction

P0358 means the engine computer detected an electrical fault in the primary or secondary circuit of ignition coil H, which fires cylinder 8. It only exists on engines with eight or more cylinders, so you will see it on V8s, V10s and V12s. Expect a misfire on cylinder 8; the coil itself is the usual cause, then the plug, the connector or the wiring.

P0358 is a ignition-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0358 and illuminates the check engine light.

If your vehicle has triggered P0358, you may notice one or more of these symptoms:

• Check engine light on, usually with a cylinder 8 misfire code (P0308) stored as well
• Rough idle with a shake from the one cylinder that is not firing
• Hesitation and loss of power when accelerating
• Check engine light flashing under load while the misfire is active
• Fuel consumption up noticeably
• Raw fuel smell from the exhaust
• Harder starting when the engine is hot

Here are the most common causes of P0358:

No - address this immediately. You can limp to a workshop, but a coil that is not firing sends unburned fuel from cylinder 8 into the exhaust, where it overheats the catalytic converter. Get it fixed within a day or two, and if the check engine light flashes, stop driving.

Follow these steps to pinpoint the root cause of P0358:

1. Read all stored codes and the freeze frame. A cylinder 8 misfire code (P0308) stored alongside P0358 confirms the cylinder is really dropping out, not just logging an electrical glitch.
2. Find cylinder 8 in the service data for your engine. Coil H follows the engine's own cylinder numbering, and on V engines that numbering differs from maker to maker.
3. Remove the cylinder 8 coil and inspect the boot for cracks, carbon tracks or oil, and the connector for green corrosion, bent or pushed-back pins and a broken locking tab.
4. Swap the cylinder 8 coil with the one from cylinder 6, clear the codes and drive. If the fault moves (P0358 becomes P0356), the coil is bad. If P0358 returns, look at the plug, connector and wiring.
5. Pull the cylinder 8 spark plug and check the gap, electrode wear and any oil or fuel fouling. A worn plug makes the coil work harder and can kill a new coil quickly.
6. Key on, engine off: confirm battery voltage at the coil supply pin against a good ground. While cranking, check that the engine computer is switching the trigger wire with an LED test light or an oscilloscope. Avoid an ordinary bulb test light, which can load the trigger circuit on coils with a built-in igniter.
7. Follow the harness towards the engine computer looking for chafing, heat damage or rodent bites, especially where it runs over the back of the engine or close to the exhaust.
8. If coil, plug, supply and wiring all pass, the coil driver in the engine computer is the remaining suspect. That needs a workshop with an oscilloscope and the wiring diagram.

Repair costs for P0358 vary depending on the root cause and your vehicle. Here are typical estimates:

P0358 behaves differently depending on your vehicle. Select your car below for model-specific causes and known issues:

These codes are often seen alongside P0358 or indicate related issues: