What it means
An electrical fault is detected in both the primary and the secondary circuit of ignition coil A (cylinder 1). The ECU cannot drive the coil correctly, so the cylinder served by coil A misfires or does not fire at all. Causes: an open or shorted primary control wire, an internal coil winding fault, a failed igniter/driver, or wiring or connector damage at the coil.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Ignition coil A serves cylinder 1, and its primary circuit carries the control module’s switching current while its secondary circuit supplies spark voltage. P0351 sets when the module detects an electrical fault in coil A’s primary or secondary circuit, which can leave cylinder 1 misfiring or without spark.
Common causes
Most likely first.
- Coil primary winding open or shorted
- Wiring or connector fault
Symptoms
- Check-engine light
- Rough running or misfire
- Hard starting
- Reduced engine power
How to diagnose it
- Review freeze-frame data and cylinder-specific misfire information to see whether the fault coincides with cylinder 1 losing spark.
- Inspect coil A at cylinder 1 and its connector for loose or pushed-back pins, corrosion, or damaged wiring.
- Check coil A’s power, ground, and control wiring against the manufacturer’s wiring information.
- Test the primary and secondary circuits of coil A using the manufacturer’s specified procedure.
- If the wiring is sound, test coil A and its ignition driver before replacing the failed component.
Common fixes
- Reconnect coil A at cylinder 1 or repair loose or damaged connector pins.
- Repair an open or short in coil A’s power, ground, or control wiring.
- Replace ignition coil A if its primary or secondary circuit fails testing.
- Repair or replace the ignition driver if testing identifies it as the cause.
Can I keep driving?
Avoid hard acceleration and long trips while cylinder 1 is misfiring; continued misfire can damage the catalytic converter. If the engine runs very roughly, stalls, or the warning light flashes, stop driving and arrange prompt diagnosis.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.