P0358 is an ignition coil circuit trouble code that can make your engine run rough, turn on the check engine light, and leave you wondering what failed. This code points to a problem with the ignition coil “H” or cylinder 8 coil circuit, depending on how your vehicle labels it. The issue can be as simple as a bad coil or as complex as a wiring or ECU fault. In this guide, you’ll learn what P0358 means, common causes, symptoms, how to diagnose it, and realistic repair options.
What Does P0358 Mean?
P0358 is defined as “Ignition Coil H Primary/Secondary Circuit Malfunction.” On most vehicles, that means the powertrain control module (PCM/ECU) has detected an electrical problem in the ignition coil circuit for cylinder 8. It’s seeing a voltage or current pattern that’s outside the expected range.
Modern engines use coil-on-plug (COP) systems. Each cylinder has its own coil, controlled directly by the ECU. When the ECU commands coil 8 to fire and the feedback doesn’t match what it expects, it sets P0358 and usually logs a misfire on that cylinder as well.
Quick Reference
- Code: P0358 – Ignition Coil H / Cylinder 8 Circuit Malfunction
- Main area: Ignition coil, wiring, ECU driver for cylinder 8
- Risk: Misfire, reduced power, possible catalytic converter damage
- Skill level: Moderate DIY to professional
- Typical fixes: Replace coil, repair wiring, replace plug, rare ECU repair
Real-World Example / Field Notes
In the shop, I see P0358 a lot on V8 trucks and SUVs. A common scenario: the customer comes in with a flashing check engine light under load, rough running, and maybe a fuel smell. Scan tool shows P0358 plus a misfire on cylinder 8. Swapping the coil from cylinder 8 to another cylinder moves the misfire and code, confirming a bad coil. Other times, especially on higher-mileage vehicles, I’ll find a cracked coil connector, oil in the plug well, or a rubbed-through harness near the valve cover causing intermittent faults.
Symptoms of P0358
- Check engine light on: Steady or flashing MIL, often with stored misfire codes.
- Rough idle: Noticeable shaking or vibration at stoplights or in park.
- Loss of power: Poor acceleration, especially when climbing hills or towing.
- Engine misfire: Stumbling, hesitation, or “skipping” under load.
- Increased fuel consumption: You may see a drop in MPG due to incomplete combustion.
- Fuel or sulfur smell: Unburned fuel reaching the exhaust and catalytic converter.
- Hard start or no start (rare): More noticeable on engines already in poor tune.
Common Causes of P0358
Most Common Causes
- Failed ignition coil on cylinder 8: Internal short or open in the coil windings is the number one cause. Heat, age, and vibration take their toll.
- Worn or fouled spark plug: Excessive plug resistance or a cracked insulator can stress the coil and trigger circuit faults and misfires.
- Damaged coil connector: Broken locking tab, loose terminals, or corrosion at the coil plug can cause intermittent or open circuits.
- Harness damage near the coil: Chafed, pinched, or oil-soaked wiring right at the valve cover or intake can cause short-to-ground or open circuits.
Less Common Causes
- Shorted or open coil driver wire to ECU: Damage further up the harness, rodent damage, or previous repairs can affect the control wire for cylinder 8.
- Poor engine ground or power supply: Bad grounds or low system voltage can create erratic coil operation and trigger circuit codes.
- ECU/PCM internal fault: A failed ignition driver inside the ECU is rare but possible, especially after jump-start mistakes or water intrusion.
- Oil or coolant in plug well: Valve cover gasket or intake leaks can fill the plug tube, causing arcing, misfires, and abnormal coil current.
- Aftermarket or mismatched coils: Cheap coils with incorrect resistance or poor build quality can cause recurring P0358 issues.
Diagnosis: Step-by-Step Guide
You’ll want a basic scan tool, a digital multimeter (DMM), and ideally an OEM-level scan tool or software that can read misfire counters and Mode $06 data. A test light and a noid light for ignition coils can also help. Always work with the engine cool when removing coils and plugs.
- Confirm the code and check for companions. Scan for codes and note any related misfire codes (P0308) or other coil circuit codes (P0351–P0357). Freeze-frame data shows when the fault occurred (RPM, load, temperature).
- Visual inspection of coil 8 and wiring. Locate cylinder 8 (check firing order and layout in a service manual). Inspect the coil body, boot, and connector. Look for cracks, burn marks, oil, coolant, or loose/broken connectors.
- Swap test the coil. If access allows, swap the cylinder 8 coil with another cylinder. Clear codes and drive or run the engine. If the code and misfire move to the new cylinder, the coil is bad.
- Check spark plug condition. Remove the cylinder 8 plug. Inspect for wear, heavy deposits, cracks, or incorrect gap. Replace if questionable, and compare to other cylinders for consistency.
- Verify power and ground at the coil. With the key on, use a multimeter or test light to check for 12V at the coil power feed and a good ground (if applicable). No power may indicate a blown fuse, relay issue, or harness fault.
- Test the coil control (driver) signal. Using a noid light or scope (preferred), check the ECU’s control signal to the coil while cranking or running. No signal suggests a wiring or ECU driver issue; a normal signal with no spark points back to the coil or plug.
- Continuity test of control wire. With the ignition off and connector unplugged at both ends, measure resistance from the coil control pin to the ECU connector pin. High resistance or open circuit indicates wiring damage. Also check for short-to-ground or short-to-power.
- Check Mode $06 and misfire counters. On capable scan tools, review Mode $06 data for misfire counts on cylinder 8. This helps confirm an intermittent issue even if the engine seems to run fine during testing.
- Inspect for oil or coolant leaks into plug wells. If you see fluid around the plug or coil, address the source (valve cover gasket, tube seals, intake gasket) or you’ll keep frying coils.
- Consider ECU testing last. Only after verifying good power, ground, wiring, and known-good coil and plug should you suspect an ECU fault. Some shops can bench-test or substitute a known-good ECU for confirmation.
Pro tip: If one coil has failed on a high-mileage V8 and the others are original, it’s often wise to replace the spark plugs and at least the coils on the hardest-working cylinders to avoid chasing repeated misfires later.
Possible Fixes & Repair Costs
Most P0358 repairs are straightforward once you pinpoint the root cause. Typical fixes include replacing the cylinder 8 ignition coil, installing a new spark plug, repairing or replacing a damaged coil connector, or repairing the wiring harness. In rare cases, the ECU may need replacement or repair if the coil driver is burned out.
At a repair shop, you can expect approximate costs like these (parts and labor):
- Ignition coil replacement (single): $120–$350 depending on vehicle and coil brand.
- Spark plug replacement (single or full set): $80–$400 depending on engine layout and plug type.
- Connector or wiring repair: $100–$300, more if extensive harness work is needed.
- ECU replacement/programming: $600–$1,500+, depending on vehicle and coding requirements.
Costs vary with vehicle make, engine design (some plugs and coils are buried), labor rates in your area, and whether you use OEM or aftermarket parts. DIYers can save significantly on labor if they’re comfortable working around ignition components.
Can I Still Drive With P0358?
You can usually drive short distances with P0358, but it’s not recommended for long-term use. A cylinder 8 misfire means unburned fuel is entering the exhaust, which can overheat and damage the catalytic converter. You’ll also have reduced power and potentially unsafe drivability, especially when merging or climbing hills. If the check engine light is flashing, that indicates an active misfire and you should minimize driving and get the issue diagnosed as soon as possible.
What Happens If You Ignore P0358?
Ignoring P0358 can turn a relatively simple coil or plug repair into a much more expensive problem. Continuous misfires overheat the catalytic converter, can melt internal substrates, and may eventually trigger additional codes like P0420/P0430. Prolonged misfiring also puts extra stress on the crankshaft, engine mounts, and can foul oxygen sensors, leading to poor fuel economy and higher emissions.
Related Codes
- P0399 – Ignition Coil “R” Primary/Secondary Circuit
- P0364 – Reserved
- P0363 – Misfire Detected Fueling Disabled
- P0362 – Ignition Coil “L” Primary/Secondary Circuit
- P0361 – Ignition Coil “K” Primary/Secondary Circuit
- P0360 – Ignition Coil “J” Primary/Secondary Circuit
- P0359 – Ignition Coil “I” Primary/Secondary Circuit
- P0357 – Ignition Coil “G” Primary/Secondary Circuit
- P0356 – Ignition Coil “F” Primary/Secondary Circuit
- P0355 – Ignition Coil “E” Primary/Secondary Circuit
Key Takeaways
- P0358 points to an electrical problem in the ignition coil circuit for cylinder 8 (or coil H).
- Most cases are caused by a failed coil, bad spark plug, or damaged connector right at the coil.
- Driving with an active misfire risks catalytic converter damage and poor drivability.
- Basic tests—coil swap, visual inspection, power/ground checks—can quickly narrow down the fault.
- Fixes are often affordable if handled early, before converter or ECU damage occurs.
Vehicles Commonly Affected by P0358
P0358 shows up most often on V8 engines with coil-on-plug systems. In the real world, I see it frequently on:
- Ford F-150, Expedition, Explorer, and E-series vans with 4.6L, 5.4L, and 6.2L V8 engines.
- Chevrolet/GMC Silverado, Sierra, Tahoe, Suburban, Yukon, and Express/Savana with LS-based V8s.
- Dodge/Ram trucks and SUVs with 4.7L, 5.7L HEMI, and similar V8 engines.
- Toyota/Lexus Tundra, Sequoia, Land Cruiser, and LS/GS sedans with V8 engines.
- Other V8-equipped vehicles, including some BMW, Mercedes-Benz, and Nissan/Infiniti models using individual coils.
That said, any vehicle with an eight-cylinder engine and individual ignition coils can potentially set P0358 if the coil 8 circuit has an issue.
FAQ
Can I clear P0358 and keep driving if the engine feels fine?
You can clear the code, but if the underlying problem isn’t fixed, P0358 will usually return. Even if the engine feels okay now, intermittent coil or wiring issues tend to worsen over time and can eventually cause a hard misfire and catalytic converter damage.
Is P0358 always caused by a bad ignition coil?
No. A failed coil is the most common cause, but wiring problems, a loose or corroded connector, a fouled spark plug, or even an ECU driver fault can also trigger P0358. A quick coil swap test and basic electrical checks help avoid replacing good parts.
How do I know which cylinder is number 8 on my engine?
Cylinder numbering varies by manufacturer and engine design. On many V8s, cylinder 1 is at the front, and cylinder 8 is the rear cylinder on the opposite bank. Check a service manual, under-hood label, or a reliable online diagram for your specific engine layout.
Can a bad spark plug alone set a P0358 code?
Yes, it can. A severely worn or cracked plug can change the load on the coil and alter current flow enough for the ECU to see an abnormal pattern and set a coil circuit code. That’s why it’s smart to inspect and, if needed, replace the plug when you’re dealing with P0358.
How urgent is it to fix P0358 once the light comes on?
You should address P0358 as soon as you can. While the car may still run, ongoing misfires can quickly overheat and damage the catalytic converter, which is far more expensive than a coil or plug. If the check engine light is flashing or the engine runs very rough, reduce driving and get it repaired immediately.