P2326: Ignition Coil I Secondary Circuit

What it means

A fault is detected on the secondary (high-voltage) side of ignition coil I. The spark delivered to the plug is missing or too weak, causing a misfire on the cylinder served by coil I. 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

Ignition coil I raises battery voltage to produce the high-voltage spark for the cylinder it serves. P2326 indicates a problem in the coil I secondary circuit, so the spark may be weak or missing even if the coil’s primary control circuit is operating.

Common causes

Most likely first.

1. Spark plug worn or fouled
2. Secondary breakdown inside coil I

Symptoms

• Check-engine light
• Engine misfire or rough running
• Hesitation or reduced power

How to diagnose it

1. Confirm P2326 with a scan tool and review freeze-frame and misfire data to identify when the cylinder served by coil I is misfiring.
2. Inspect the coil I boot, spark plug, and plug well for cracks, carbon tracking, oil, moisture, fouling, or visible damage.
3. Remove and inspect the spark plug served by coil I, checking its condition and electrode gap against the manufacturer’s specification.
4. Test coil I and its secondary path using the manufacturer’s diagnostic procedure, and compare results with a known-good cylinder where appropriate.

Common fixes

• Clean moisture or contamination from the coil I plug well and repair the source of any leak.
• Replace the worn, fouled, or damaged spark plug served by coil I.
• Replace the cracked coil I boot or coil if testing confirms secondary breakdown.

Can I keep driving?

Avoid hard acceleration and long trips while the engine is misfiring; unburned fuel can overheat and damage the catalytic converter. Stop driving if the check-engine light flashes or the engine runs very roughly.