P0359 code: Ignition Coil I Primary/Secondary Circuit (Cylinder 9)
P0359 means ignition Coil I Primary/Secondary Circuit (Cylinder 9). The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0359 means
This code reports an electrical fault — open or short — in the circuit of ignition Coil I, the coil for cylinder 9. Since it requires a ninth cylinder, P0359 only exists in practice on V10 and V12 engines; if it appears on anything smaller, suspect a scan-tool misread. The ECM triggers each coil by switching its primary winding and monitors the circuit's response every firing event, so the code is specific: coil I's circuit failed electrically, which is a different failure mode from a worn spark plug (a plug degrades the spark without breaking the circuit). Causes follow the familiar pattern — a failed coil, a loose or corroded connector, chafed wiring in that bank's harness, a blown fuse in the coil supply, or rarely the ECM's coil driver. Because cylinder 9 loses spark, its companion misfire code P0309 usually sets as well; on a ten- or twelve-cylinder engine the miss can be subtle at idle, so the codes may be the only obvious evidence.
P0359 symptoms
- Misfire on cylinder 9 — may feel subtle on a V10/V12
- Slightly uneven idle or faint periodic shudder
- Check-engine light, flashing under load while misfiring
- Fuel smell from the exhaust
- Reduced power; typically paired with P0309
What it costs to fix P0359
Typical range: $70–$500 · about ~0.3–2.5 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Ignition coil (single) | $30–$150 | ~0.3–1.5 hrs |
| Wiring or connector repair | $5–$50 | ~0.5–2 hrs |
| Spark plugs (while in there) | $20–$100 | ~0.5–1.5 hrs |
V10 and V12 engine bays are usually crowded — coils can hide under covers, plumbing, or cowl panels — so labor runs longer than on a simple four-cylinder even though the coil itself is a similar modest part. On these engines it's common to at least inspect the neighboring coils and plugs while the covers are off, since they share age and heat exposure.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0359 for my exact vehicle →
How to fix P0359
Moderate — doable at home with common tools and patience
- Make sure the code fits your engine
Coil I fires cylinder 9, which only exists on V10 and twelve-cylinder engines with individual coils. If your engine has fewer cylinders, or fires its plugs through wires from a shared coil pack, recheck the reading with a better scanner and look up what the code means for your make before buying anything.
- Inspect coil I's connector and harness for heat
On work trucks and vans that tow or idle for long stretches, the coil harness takes a beating from underhood heat. Check the cylinder 9 connector for a brittle or broken locking tab, and follow its leg for missing clips, melted conduit, or wire resting against the exhaust manifold or a heat shield.
- Test feed and ground with a test light
Unplug coil I and, key on, touch a test light from the feed pin to a clean ground, then from battery positive to the ground pin if the coil has one. A bright light both ways confirms the supply; a dim or dead light sends you to the fuse, relay, or ground eyelet before any coil gets replaced.
- Move coil 9 to a cylinder that fires cleanly
Put cylinder 9's coil on a healthy cylinder and that cylinder's coil on 9. If the next scan shows a different coil-circuit code matching where coil I went, replace it; if P0359 sets again with a good coil on cylinder 9, the trigger wire or driver is next.
- Trace the trigger wire before suspecting the ECM
Check the control wire from the cylinder 9 connector to the ECM for continuity and for a short to ground or to voltage, using the wiring diagram for your engine. A driver fault inside the ECM is uncommon and usually follows a shorted coil, so a replacement module should only go in alongside a healthy coil and after the wire tests clean.
DIY or shop? Heavy-duty V10 owners can usually do all of this at home: coils on many truck V10s are reachable with hand tools, and a test light plus a meter cover the electrical checks. On a twelve-cylinder car, access and covers make it more involved, but the logic is the same. Bring in a shop when the fault sits in the wire run to the computer, when the module itself is suspected — replacement normally needs programming — or when you can't reach cylinder 9 without removing intake parts.
Tools for the DIY steps: Scan tool that reads freeze frame · 12-volt test light · Digital multimeter · Wiring diagram for your engine · Socket set with extensions
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0359.
Start a case with P0359 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 P0359?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0359: common questions
What engines can even set P0359?
Only engines with nine or more cylinders — in practice V10s and V12s, since coil I serves cylinder 9. If this code shows up on a four-, six-, or eight-cylinder vehicle, the code was misread or the scan tool glitched; there is no coil I to fault.
Why can't I feel the misfire if P0359 and P0309 are set?
On a V10 or V12, the remaining cylinders smooth over one missing firing pulse far better than a four-cylinder could, so the misfire can be nearly imperceptible at idle. The damage still happens, though — unburned fuel from cylinder 9 is heating the catalytic converter whether you feel the miss or not.
Is P0359 expensive to repair on a V12?
The coil is an ordinary, modestly priced part — the variable is labor, because many-cylinder engine bays bury coils under covers and plumbing. Expect more shop time than a four-cylinder coil job, and consider having the neighboring bank hardware inspected while it's open to avoid paying the access labor twice.
Can I drive until the repair?
A code can't tell Redline whether your car should be driven. Even with a steady check-engine light, the misfire keeps feeding raw fuel to the converter, so get it repaired promptly. A flashing light means the converter on that bank is being damaged right now — stop driving and park it until it's fixed.
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0359 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 P0359 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.