P0351 code: Ignition Coil A Primary/Secondary Circuit
P0351 means ignition Coil A Primary/Secondary Circuit. The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0351 means
Your engine computer (ECM) fires each ignition coil by pulsing its primary circuit, and it watches that circuit to verify the coil responded. P0351 means the ECM detected an electrical fault — an open or a short — in the primary or secondary circuit of Coil A, which on coil-on-plug engines is the coil for cylinder 1. This is a wiring/coil electrical fault, not the same thing as a worn spark plug: the circuit itself is broken or shorted, not just sparking weakly. The most common culprits are a failed coil, a connector that has come loose or corroded, or chafed wiring on that coil's leg of the harness. A blown fuse feeding the coils or, rarely, the coil driver inside the ECM can also be responsible. Because cylinder 1 stops firing, P0351 very often appears alongside its companion misfire code, P0301.
P0351 symptoms
- Misfire on cylinder 1 — rough running, especially at idle
- Flashing check-engine light during an active misfire
- Noticeable loss of power
- Fuel smell from the exhaust from unburned fuel
- Usually paired with misfire code P0301
What it costs to fix P0351
Typical range: $60–$400 · about ~0.2–2 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Ignition coil (single) | $30–$150 | ~0.2–0.5 hrs |
| Wiring or connector repair | $5–$50 | ~0.5–2 hrs |
| Spark plugs (while in there) | $20–$100 | ~0.5–1.5 hrs |
Cylinder 1 is easy to reach on most inline engines, so a coil swap is one of the quicker jobs — the coil part itself is modest. Which cylinder is number 1 varies by make and engine layout, though; if it lands on the rear bank of a transverse V6, intake removal can push labor to 1–3 hours.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0351 for my exact vehicle →
How to fix P0351
Easy — basic tools, most owners can do this
- Reseat the coil 1 connector
Unplug the connector on cylinder 1's coil, check for corrosion, bent pins, or a broken locking tab, then snap it back on firmly. A loose or dirty connector is a common cause of this code and costs nothing to fix.
- Swap coil 1 with a neighboring cylinder
Move coil 1 to another cylinder and put that cylinder's coil on number 1, then clear the code and drive. If the code changes to match the coil's new position (say P0352), the coil itself has failed — replace it.
- Check for power at the coil 1 connector
With the key on, probe the connector's feed wire for battery voltage using a multimeter or test light. Voltage present means the feed is good and the fault is the coil or its trigger wire; no voltage means a fuse or upstream wiring problem.
- Trace coil A's harness leg
Follow the wiring from the coil 1 connector back along the harness, looking for chafed insulation where it crosses brackets or the valve cover. Repair any damage with solder and heat-shrink rather than tape for a lasting fix.
DIY or shop? Reseating the connector and doing the coil swap take ten minutes and no special skills — start there, because they solve most P0351s. A multimeter check is still comfortable DIY. If the wiring damage runs deep into the harness or everything tests fine and the code persists (a possible ECM driver fault), that's the point to involve a shop.
Tools for the DIY steps: OBD-II scanner · Multimeter or test light · Small socket for the coil hold-down bolt · Electrical contact cleaner
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0351.
Start a case with P0351 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 P0351?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0351: common questions
Is P0351 a bad coil or a bad spark plug?
P0351 is an electrical circuit code, so it points at the coil, its connector, or its wiring — not the spark plug. A worn plug can cause a misfire (P0301) but won't normally set a circuit code, because the circuit still measures electrically intact. That said, plugs are cheap and worth replacing while the coil is out.
How do I confirm it's the coil and not the wiring?
The classic test: swap coil 1 with a neighboring cylinder's coil and clear the code. If the code moves with the coil (say P0351 becomes P0352), the coil is bad. If P0351 stays on cylinder 1, the problem is in that cylinder's connector, wiring, or — rarely — the ECM driver.
Can I drive with P0351?
Redline can't judge that from the code alone. With a steady check-engine light, the dead cylinder is feeding raw fuel to the catalytic converter the whole time, so get it repaired promptly. If the light flashes, stop driving and have it checked — a ruined catalyst costs far more than a coil.
How much does it cost to fix P0351?
Often modest: a single coil is an inexpensive part and cylinder 1 is accessible on most engines, so labor is short. It costs more if the real fault is chafed wiring that takes time to trace, or if your engine layout buries that coil under the intake.
Symptoms that trigger P0351
Drivers who get this code often notice one of these. Each has its own causes and cost guide:
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0351 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 P0351 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.