OBD codes / P0356
P0356
SeriousIgnition Coil F Primary/Secondary Circuit (Cylinder 6)
The misfiring cylinder is flooding the exhaust with unburned fuel, and the catalytic converter absorbs that abuse until it overheats. Keep driving minimal and gentle; a flashing check-engine light means the converter is being damaged in real time, so treat the repair as prompt, not someday.
What this code means
P0356 means the engine computer detected an open or short in the primary or secondary circuit of ignition Coil F — the coil serving cylinder 6. The ECM personally switches each coil's primary winding to command every spark and monitors the circuit's response, so this code is a precise electrical complaint: coil F's circuit did not behave like an intact circuit. That distinction matters — a worn spark plug degrades the spark quality but does not set a circuit code, so P0356 steers you toward the coil, its connector, and its wiring rather than the plug. A blown fuse in the coil supply or, rarely, a failed coil driver inside the ECM are the remaining possibilities. Cylinder 6's location depends on your engine: last in line on an inline-six, or on either bank of a V6/V8 depending on the maker's numbering scheme. Because the cylinder loses spark entirely, the matching misfire code P0306 usually sets at the same time.
Symptoms you might notice
- Misfire on cylinder 6 — rough idle and stumble under acceleration
- Check-engine light, flashing while the misfire is active
- Down on power, particularly under load
- Fuel smell from the tailpipe
- Usually stored together with P0306
What it costs to fix
Typical range: $60–$550 · about ~0.2–3 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Ignition coil (single) | $30–$150 | ~0.2–3 hrs |
| Wiring or connector repair | $5–$50 | ~0.5–2 hrs |
| Spark plugs (while in there) | $20–$100 | ~0.5–1.5 hrs |
Access decides this bill. On inline sixes and most V8s the coil is right on top: modest part, 0.2–0.5 hours. On many transverse V6 engines cylinder 6 sits on the rear (firewall) bank, and reaching that coil can require pulling the upper intake — 1–3 hours of labor — in which case doing all the rear-bank plugs and inspecting the other rear coils at the same time is the economical move.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0356 for my exact vehicle →
Frequently asked
Where is cylinder 6 on my engine?
It depends on the manufacturer — cylinder numbering isn't standardized. On an inline-six it's the last cylinder in the row; on V6 and V8 engines it can be on either bank depending on the maker's scheme. Check your specific engine's numbering before swapping coils, or you may test the wrong one.
How do I test whether coil 6 is actually bad?
Swap it with a coil from another cylinder and clear the codes. If P0356 becomes the other cylinder's circuit code, the coil is the problem and one new coil fixes it. If P0356 stays, focus on cylinder 6's connector and wiring — and only suspect the ECM driver after those check out.
Can I keep driving with P0356?
For a short time with a steady check-engine light, yes — gently. But the dead cylinder is dumping fuel into the catalytic converter, and a flashing light means the converter is overheating right now. The longer it runs that way, the better the odds you're buying a catalyst too.
Should the spark plugs be replaced along with the coil?
If the plugs are anywhere near their service interval, yes — especially when reaching the coil required real teardown. The plug isn't what set this code, but a worn plug makes its coil work harder, and the labor to access them is already paid for while things are apart.
Seeing P0356 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0356 for my vehicleRelated trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0356 from your phone — see our honest guide to the best OBD2 Bluetooth adapters.
Generic OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.