P0351 means Ignition Coil A Primary/Secondary Circuit Malfunction. The computer has detected a fault in the circuit for ignition coil A. On most coil-on-plug engines, coil A is the coil for cylinder 1. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0351 means
Most modern engines use coil-on-plug ignition, with one coil per cylinder (or per pair of cylinders) switched by a driver inside the engine computer. The computer monitors each coil circuit, and a fault there usually comes with a misfire on the matching cylinder, so coil and misfire codes are diagnosed together.
P0351 symptoms
- Misfire, often with P0301
- Rough idle
- Loss of power
- Flashing check engine light under load
Common causes of P0351
- Failed ignition coil
- Damaged connector or wiring
- Coil driver fault in the engine computer (less common)
How to diagnose P0351
- Check for a matching misfire code
- Inspect the coil connector and wiring
- Swap the coil with another cylinder and see if the code moves
- Check coil power and the control signal
Can you drive with P0351?
Short distances only; misfires can overheat the catalytic converter.
P0351 tips
Swapping coils is the quickest test: move coil A to another cylinder, clear the code and see whether the circuit code and the misfire follow it. If they stay with cylinder 1, check the wiring and the driver signal from the computer.
Will P0351 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0351 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0352 | Ignition Coil B Primary/Secondary Circuit Malfunction |
| P0301 | Cylinder 1 Misfire Detected |
| P0300 | Random/Multiple Cylinder Misfire Detected |
Guides that help
- bad ignition coil symptoms
- bad spark plug symptoms
- engine misfire and flashing check engine light
- compression and leak-down tests
When it is more than a sensor
If a coil and plug swap does not move the misfire and a compression or leak-down test shows a burnt valve or failed head gasket, the decision becomes repair versus replacement; see engine replacement cost and compare engines by code on our engines page.
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