OBD-II Code P0358 — What It Means & How to Fix It

What Does This Error Mean?

P0358 means the PCM detected an electrical fault in the primary circuit of ignition coil H. Coil H is the 8th coil in the ignition firing order — found on V8 and larger engines. The primary circuit is the low-voltage control side driven directly by the PCM. You will likely also see a cylinder 8 misfire code and rough running at idle or under load.

Affected Models

All 1996+ V8, V10, and V12 vehicles with individual coil-on-plug ignition
Common in Ford F-150, F-250, Mustang GT and Cobra V8 engines
Common in GM Silverado, Sierra, Camaro, and Corvette LS-series engines
Common in Dodge Ram, Charger, and Challenger Hemi V8 engines
Common in any 8-cylinder or larger engine with one coil per cylinder

Common Causes

Failed ignition coil H — open or short in the primary winding
Damaged or melted wiring in the coil H control circuit
Corroded, loose, or damaged connector at the coil H plug
Worn, cracked, or fouled spark plug in the coil H cylinder placing excessive load on the coil
PCM coil driver failure on the coil H output channel (uncommon)

How to Fix It

Determine which physical cylinder coil H is on your engine. Coil H is the 8th position in the firing order — which may not be physical cylinder 8. Look up the firing order for your exact engine make, model, and year before touching anything.

On a typical GM V8 with firing order 1-8-7-2-6-5-4-3, the 8th firing position is cylinder 3. Always verify before pulling a coil.
Check the coil H wiring connector. Look for pushed-back or corroded terminals, melted insulation, or a connector that is not fully snapped in. Clean the connector pins with electrical contact cleaner and reseat firmly.

Rear cylinder coils — especially on transverse or tight-bay V8 engines — can have connectors that loosen from vibration or are bumped loose during other repairs.
Swap coil H with a coil from a different cylinder of the same type. Clear all fault codes and drive the vehicle. If P0358 disappears and a new coil letter code appears on the cylinder you swapped from, coil H itself is faulty.

This swap test is the single best low-cost diagnostic for any primary coil circuit code. It isolates the coil from the wiring in one step.
Remove and inspect the spark plug in the coil H cylinder. Replace it if it is worn down, oil-fouled, or cracked. Always install a new plug at the same time you replace the coil.

Installing a new coil on an old or faulty plug stresses the coil and can lead to repeat failure within a short time.
Install a new quality coil in the coil H position. Secure all connectors. Clear all stored codes and test drive through several hard accelerations. Confirm the misfire is gone and P0358 does not reappear.

If P0358 returns on a new coil, the PCM driver circuit for coil H likely has an internal fault. This requires professional diagnosis and possibly PCM replacement or repair.

When to Call a Professional

If swapping coil H to a different cylinder position moves the fault code with it, the coil is confirmed bad. If the code stays on the same cylinder after swapping, suspect a wiring or PCM driver issue. A technician with an oscilloscope can check whether the PCM is sending a proper trigger signal to coil H. Diagnosis usually costs $80-$130. Coil replacement parts typically cost $25-$80.

Frequently Asked Questions

Is P0358 only on V8 engines?

Mostly yes. Coil H is the 8th coil in the firing order, so you need at least 8 cylinders. However, some V6 engines with a dual-coil-per-cylinder setup (wasted spark with individual coils) can generate coil letters up to H as well. The most common vehicles with P0358 are V8 trucks and muscle cars.

What happens if I ignore P0358?

The misfiring cylinder sends raw fuel into the exhaust. This overheats the catalytic converter and can destroy it within days of continuous driving. You will also notice worsening fuel economy and reduced power. If the check engine light is flashing, stop driving and get a tow — catalyst damage is happening right now.

Can a bad spark plug really cause P0358?

Yes. A spark plug with a worn electrode, cracked insulator, or heavy fouling forces the ignition coil to work much harder to fire the plug. This extra electrical stress breaks down the coil's primary winding over time. Always inspect and replace plugs when you find a coil code — especially if the vehicle has high mileage or the plugs have never been changed.