P0358 code: Ignition Coil H Primary/Secondary Circuit (Cylinder 8)
P0358 means ignition Coil H Primary/Secondary Circuit (Cylinder 8). The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0358 means
P0358 is the ECM reporting an open or short in the primary or secondary circuit of ignition Coil H — cylinder 8's coil, which makes this a code for V8 and larger engines. On coil-on-plug systems the computer drives every coil individually through its primary winding and checks the circuit each time it commands a spark, so the code identifies the exact coil circuit at fault. Keep the diagnosis electrical: a worn spark plug weakens the spark but doesn't open the circuit, so the suspects are the coil itself, its connector, the wiring leg feeding it, the fuse supplying the coil bank, and — rarely — the driver transistor inside the ECM. Cylinder 8 is typically the last cylinder on one bank of a V8, though which bank depends on the manufacturer's numbering; on some engines it sits close to the firewall where connectors get disturbed during other work. Expect the matching misfire code P0308 alongside, since the cylinder has lost spark entirely.
P0358 symptoms
- Cylinder 8 misfire — rough idle with a rhythmic miss
- Noticeable power loss under acceleration or load
- Flashing check-engine light during active misfire
- Raw-fuel smell from the exhaust
- Reduced fuel economy; P0308 usually stored with it
What it costs to fix P0358
Typical range: $60–$450 · about ~0.2–2 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Ignition coil (single) | $30–$150 | ~0.2–1 hrs |
| Wiring or connector repair | $5–$50 | ~0.5–2 hrs |
| Spark plugs (while in there) | $20–$100 | ~0.5–1.5 hrs |
On most V8s the coils are exposed on top of the engine, so a confirmed bad coil is a quick, inexpensive swap. Rear-of-bank cylinders like number 8 can be tighter to reach on some trucks and rear-drive sedans with deep engine bays, and intermittent wiring faults add tracing time regardless of layout.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0358 for my exact vehicle →
How to fix P0358
Moderate — doable at home with common tools and patience
- Ask what was worked on recently
Coil H fires cylinder 8, often the rearmost cylinder on a V8 bank close to the firewall, where hands, hoses, and tools brush past during heater, intake, or valve-cover work. If P0358 appeared soon after another repair, start by checking that the coil connector is fully latched and the harness wasn't pinched when things went back together.
- Wiggle-test the coil H harness at idle
With the engine idling and a scanner showing misfire counts or code status, gently flex the connector and the harness leg to cylinder 8 along its run toward the firewall, keeping your hands off the coils themselves. A stumble, a count jump, or the code resetting at one spot pins an intermittent break that a static meter check can miss.
- Swap coil H with a more accessible coil
Install the cylinder 8 coil on an easier cylinder and that one's coil on 8, then drive long enough to cover the freeze-frame conditions. The fault changing to the other coil's code means coil H is bad; P0358 refusing to move puts the terminals, harness, or driver back in focus.
- Check terminal grip and the ground path
Spread or burned terminals can open the circuit only when hot or vibrating, so slide a matching test terminal into each socket and feel for drag. Also check engine-to-body ground straps and any ground eyelet near the back of the head; a loose ground there can upset a coil at the end of the bank.
- Have a shop scope the primary circuit
If the cause still hides, a technician can put a lab scope or current clamp on coil H's circuit and compare its charge ramp with a healthy coil. An abnormal ramp separates shorted windings, a high-resistance wire, and a driver problem far more reliably than swapping parts.
DIY or shop? The coil swap and connector checks are DIY when you can reach cylinder 8, which on many trucks is fine and on some vans and tightly packed cars means working blind against the firewall. The wiggle test is free and worth doing yourself. Paying for diagnosis makes sense once the fault is intermittent and a fresh coil hasn't fixed it — a scope finds in minutes what parts-swapping can miss for weeks.
Tools for the DIY steps: OBD-II scanner with live data · Terminal test kit or matching male terminal · Digital multimeter · Swivel socket and long extensions · Flashlight and inspection mirror
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0358.
Start a case with P0358 and your car. Redline weighs these causes against what your car shows, and names the check that would settle it before you buy parts.
Can I drive with P0358?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0358: common questions
Could a fuse cause P0358?
It can — the ignition coils are fed through a fuse (sometimes a relay), and a blown one kills coil power. Usually that takes out several coils at once and sets multiple codes, so a lone P0358 more often points to coil 8 itself or its connector and wiring. Either way, the fuse box is a 30-second check worth doing first.
My V8 runs almost normally — do I really need to fix P0358?
It's worth fixing promptly. A V8 masks one dead cylinder well, but the misfire is still pushing raw fuel into the catalytic converter every second the engine runs, and converters fail by overheating. The fix is typically one cheap coil; the consequence of ignoring it can be an exhaust repair costing many times more.
Should I replace all eight coils?
Only if you want to. If the swap test confirms coil 8 failed and the others behave, one coil is a complete repair. On a high-mileage engine some owners do the full set (and plugs) as preventive maintenance since coils of the same age tend to fail in sequence — that's a convenience decision, not a requirement.
Will P0358 pass or fail an emissions test?
An active check-engine light generally means an automatic fail wherever OBD testing is used. Repair the circuit, clear the code, and drive enough for the readiness monitors to complete before retesting.
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0358 from your phone. See our guide to the best OBD2 Bluetooth adapters. Run a repair shop? See Redline for shops.
Generic OBD-II reference. Manufacturer-specific behavior varies. Confirm with a scan tool and, for safety-related codes, a professional inspection. Cost ranges are reference ranges, not quotes.
Seeing P0358 on your car?
Every problem becomes a Case. Tell Redline what the car is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.