P0351
Serious Severity (Level 4)Ignition Coil "A" Primary/Secondary Circuit Malfunction
OBD-II diagnostic trouble code P0351indicates a fault detected by the vehicle's onboard computer. This code applies to all OBD-II compliant vehicles and should be addressed promptly to avoid potential engine or emissions system damage.
Severity Level 4 — Serious
This code indicates a serious issue that can cause noticeable driveability problems and potential engine damage if not addressed. The vehicle should be taken to a mechanic as soon as possible. Extended driving is not recommended.
Common Symptoms
- Check Engine Light on (may flash under load)
- Engine misfire, rough running, shaking
- Loss of power and acceleration
- Poor fuel economy
- Engine may not start if coil is completely dead (COP systems)
Possible Causes
- Faulty ignition coil — internal winding short or open circuit from heat stress
- Damaged wiring or loose connector at coil — broken wire at connector from engine vibration
- Blown ignition coil fuse (shared for multiple coils, if blown all on that circuit fail)
- Faulty ignition control module (ICM) or PCM coil driver transistor failed
- Spark plug with excessive gap forcing coil to work harder and overheat
Common Fixes
- Replace ignition coil "A" (cylinder 1 on most engines, check firing order) ($50-200)
- Repair damaged wiring or connector at coil ($30-150)
- Replace blown ignition fuse ($1-5)
- Replace spark plugs if worn — excessive gap damages coils ($40-200 for set)
- Replace PCM if internal driver failed (rare, $500-1500)
Estimated Repair Cost
$1 – $1500(typical range; varies by vehicle make and model)
These are estimated costs based on generic repair data. Actual costs may vary depending on your vehicle, location, and labor rates.
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