What it means
A fault is detected on the secondary (high-voltage) side of ignition coil A. The spark delivered to the plug is missing or too weak, causing a misfire on the cylinder served by coil A. Causes: a worn spark plug or wide gap, a cracked coil or boot, carbon tracking, or an open or leaking secondary winding.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The secondary side of ignition coil A sends high voltage through its boot or lead to the assigned spark plug. The engine control module detects a problem with coil A's secondary ignition performance and sets this code when the spark is absent or too weak to ignite the mixture reliably.
Common causes
Most likely first.
- Worn or fouled spark plug
- Coil secondary winding failure
Symptoms
- Check-engine light on, possibly flashing
- Engine misfire or rough idle
- Hesitation under acceleration
- Reduced power
How to diagnose it
- Record freeze-frame data and check live misfire counts to confirm whether the cylinder served by coil A misfires under particular conditions.
- With the engine off, inspect coil A's boot or lead, plug well, and spark plug for cracks, carbon tracks, oil, or moisture.
- Remove the spark plug served by coil A and check for fouling, wear, or an excessive gap against the manufacturer's specification.
- Test coil A's secondary winding and inspect its insulation using the manufacturer's procedure.
- If the plug and coil pass, check the coil's primary supply and control circuit before considering an ECU fault.
Common fixes
- Replace a worn or fouled spark plug and correct its gap to specification.
- Clean and dry the plug well and replace a cracked or carbon-tracked coil boot.
- Replace coil A if its secondary winding or insulation fails testing.
- Repair a confirmed fault in the coil A supply or control wiring.
Can I keep driving?
If the check-engine light flashes or the engine shakes from a misfire, stop driving when safe; continued misfire can overheat and damage the catalytic converter. If the light is steady and the engine runs smoothly, avoid heavy loads and arrange diagnosis soon.
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.