P0356 code: Ignition Coil F Primary/Secondary Circuit (Cylinder 6)
P0356 means ignition Coil F Primary/Secondary Circuit (Cylinder 6). The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0356 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.
P0356 symptoms
- 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 P0356
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 →
How to fix P0356
Easy — basic tools, most owners can do this
- Identify cylinder 6 and the type of coil fitted
Cylinder 6 is the last one on an inline six but can sit on either bank of a V6 or V8, so confirm it on a diagram. Then count the wires at coil F's connector: two usually means the ECM switches the coil directly, while three or four means the coil has its own built-in driver — and that changes how you test it.
- Check the cylinder 6 well for engine oil
Lift coil F out and look down the well. Oil pooled around the plug means a leaking valve cover gasket or spark plug tube seal, and over time it softens the boot, lets spark track to ground, and cooks coils early. Fix the seal when you replace the coil, or the new one will soak in the same oil.
- Watch the trigger signal with an LED test light
Back-probe the control wire at the cylinder 6 connector with a noid or LED test light and crank the engine. A steady flicker means the ECM is commanding the coil, so the fault is the coil or its power or ground; no flicker points to the trigger wire or the driver itself.
- Ohm out a two-wire coil against another
On coils without a built-in driver, measure primary and secondary resistance per the service manual, then repeat on a coil from a healthy cylinder. Primaries typically read well under a few ohms and secondaries in the thousands; an open, or a reading far from the other coil's, condemns coil F. Coils with an internal driver can't be judged this way, so swap-test those instead.
- Fit a quality coil and verify over a drive cycle
Install an OE-grade coil — bargain coils are known to fail early, and some draw current differently enough to bring circuit codes back. Clear memory, confirm P0306 and P0356 both stay away through a full drive cycle, and if they return with a new coil, the wiring between the connector and the ECM needs tracing.
DIY or shop? On most inline sixes, and on V engines where cylinder 6 sits up top, this is beginner-friendly: one bolt, one connector, and a test light. The resistance and trigger checks need only an inexpensive meter and an LED test light. It becomes shop work if cylinder 6 is buried on a rear bank under the intake, if the trigger signal is missing and the wire has to be traced back to the ECM, or if a new coil and a clean connector still don't clear it.
Tools for the DIY steps: OBD-II scanner · LED test light or noid light · Digital multimeter · Back-probe pins · Socket for the coil hold-down bolt
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0356.
Start a case with P0356 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 P0356?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0356: common questions
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?
Redline can't make that call from the code alone. The dead cylinder is dumping fuel into the catalytic converter, so get it repaired promptly — the longer it runs that way, the better the odds you're buying a catalyst too. A flashing light means the converter is overheating right now: stop driving.
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.
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0356 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 P0356 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.