P0351: Ignition Coil "A" Primary/Secondary Circuit
The engine computer is not getting the expected electrical signal from ignition coil A, which usually serves cylinder 1.
What P0351 means
Each ignition coil on a modern engine is switched on and off by the engine computer. When it switches a coil, the computer expects to see a certain electrical response on the coil primary circuit. P0351 sets when that response for coil A is missing or out of range. In most engines coil A fires cylinder 1, but some makers label coils differently, so check your service info. RepairPal notes the fault can come from either the primary side (the wiring and the computer) or the secondary side (the plug boot, plug wire and spark plug). Because a coil that is not firing usually causes a misfire, you will often see P0301 at the same time. Shops record the freeze frame data, watch live misfire counts, then check power, ground and the trigger signal at the coil with a meter or scope. If the circuit is good, the coil is replaced. Do not drive long with it, since a dead cylinder floods the converter with fuel.
Common symptoms
- Check engine light, often with P0301
- Engine misfire or rough running
- Hesitation and power loss
- Hard starting on some engines
- Worse gas mileage
Most common causes
- Failed ignition coil A
- Broken, chafed or corroded wire in the coil circuit
- Loose or damaged coil connector
- Bad coil power feed or ground
- Spark plug problem loading the coil
- Engine computer driver fault (rare)
What to check yourself first
Check that the cylinder 1 coil connector is fully clipped in and free of corrosion. Swap the coil with another cylinder, clear the code and see whether it changes to P0352 or another coil code. Inspect the harness for rubbed through insulation.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace ignition coil | $238-$320 | Most P0351 fixes are a single coil. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | Needed when the coil tests fine but the code returns, pointing to wiring or connector trouble. |
| Replace spark plugs | $288-$399 | A worn plug with a wide gap overworks the coil, so shops often replace plugs with the coil. |
| Replace engine control module (ECM/PCM) | $1,122-$1,192 | Only if the computer coil driver is proven bad after wiring checks, which is uncommon. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0352 Ignition Coil "B" Primary/Secondary Circuit
- P0301 Cylinder 1 Misfire Detected
- P0300 Random/Multiple Cylinder Misfire Detected
- P0302 Cylinder 2 Misfire Detected