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DTC codes / P23xx · Ignition system and misfire / P2326

P2326Ignition Coil 'I' Secondary Circuit

P2326 indicates that the powertrain control module (PCM) has detected an abnormal condition in the secondary circuit of ignition coil 'I', which is the high-voltage side that fires the spark plug. The PCM monitors the coil's secondary circuit for expected electrical behavior and sets this code when the signal does not match the stored profile, often due to an open, short, or excessive resistance in the coil or its wiring.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaIgnition system and misfire

Symptoms you may notice

  • Illuminated check engine light, often with no other noticeable symptoms
  • Engine misfire or rough running, especially under load or acceleration
  • Noticeable loss of power or hesitation during acceleration
  • Shaking or vibration felt through the steering wheel or seat
  • Poor fuel economy due to incomplete combustion
  • In some cases, the engine may enter limp mode or flash the check engine light if the misfire is severe

Common causes, most likely first

  1. Faulty ignition coil 'I' with a failed secondary winding or internal short
  2. Worn or damaged spark plug or spark plug boot causing high resistance
  3. Corroded, loose, or damaged electrical connector at the coil
  4. Open or shorted secondary circuit wiring between the coil and the PCM
  5. PCM driver circuit fault for coil 'I' (less common)
  6. Moisture or oil contamination in the spark plug well causing secondary voltage leakage

How to diagnose and fix it

  1. Perform a visual inspection of coil 'I', its connector, and the spark plug well for damage, corrosion, or contamination
  2. Swap coil 'I' with a known-good coil from another cylinder and see if the code follows the coil
  3. Inspect and test the spark plug and boot for wear, cracks, or excessive resistance; replace if needed
  4. Use a multimeter to check the secondary winding resistance of coil 'I' against the manufacturer's specification
  5. Check for continuity and shorts in the secondary circuit wiring between the coil and PCM
  6. If the coil and wiring test good, perform a spark test and check for a faulty PCM driver circuit
  7. Clear the code and verify the repair by test-driving the vehicle under conditions that previously set the code

Secondary circuit faults often misdiagnosed

  • A failing spark plug or boot can mimic a bad ignition coil by causing excessive secondary resistance, so always inspect the plug before condemning the coil.
  • The code can be set by a loose or corroded ground connection at the coil mounting bolt, which many technicians overlook during diagnosis.
  • Intermittent misfires that set P2326 may only occur under specific load or temperature conditions, so a simple resistance check at idle may not reveal the fault.
  • Some vehicles use a waste-spark system where coil 'I' fires two cylinders, so a misfire may affect a cylinder other than the one indicated by the coil letter.
  • After replacing the coil, the PCM may need to relearn the misfire profile; failing to clear adaptive learning can cause the code to reappear temporarily.

Can I keep driving with P2326?

Driving with P2326 is generally acceptable for short distances, but avoid heavy acceleration or sustained high speeds because a persistent misfire can overheat the catalytic converter and cause costly damage. If the check engine light flashes or the engine runs very rough, stop driving and seek professional diagnosis immediately.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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