P2326

Code

Generic P — Powertrain

Ignition Coil I Secondary Circuit

Brand: Generic

Type: P — Powertrain

Views: UK: 36 EN: 45 RU: 36

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Page language: EN

Causes

Faulty ignition coil (secondary winding or internal damage)
Damaged or degraded spark plug or ignition boot/plug wire
Poor electrical connection at coil-to-plug terminal or coil connector
Carbon tracking or arcing on coil/boot surface
Contamination (oil, coolant, water) on coil, plug or boot
Intermittent grounding or poor chassis/engine ground

Symptoms

Check Engine Light (MIL) illuminated
Rough idle or intermittent misfire on the affected cylinder
Reduced engine power, hesitation or stumble under load
Poor fuel economy
Possible backfire or unusual exhaust noise
Intermittent starting problems (in severe cases)

What to check

Retrieve freeze-frame data and stored/related trouble codes with a scan tool
Visual inspection of ignition coil, boot, spark plug and surrounding area for damage or contamination
Check coil connector for corrosion, bent pins or poor fit
Inspect spark plug condition and gap; replace if fouled or out of spec
Swap suspect coil with another cylinder to see if fault follows the coil
Use a spark tester or oscilloscope to verify secondary spark waveform

Signal parameters

Secondary spark event: visible high-voltage discharge (spark) under test conditions
Secondary voltage: varies by engine and load; typical peak spark voltages can range from a few kV up to 30–50 kV — consult vehicle specifications
Primary coil resistance: typically low (ohms) — check service manual for correct values
Secondary coil resistance: typically kilohms — verify against manufacturer data
Oscilloscope: look for consistent secondary waveform shape and amplitude compared to a known-good cylinder

Diagnostic algorithm

Connect a scan tool, read DTCs and freeze frame data. Note cylinder number and driving conditions when the fault set.
Perform a visual inspection: check coil, boot, plug, wiring harness and connector for damage, oil, coolant or carbon tracking.
Remove and inspect the spark plug for fouling, electrode wear, or incorrect gap; replace if necessary.
Swap the suspect coil with a known-good coil from another cylinder. Clear codes and run the engine. If the code moves to the other cylinder, replace the coil.
Measure coil primary and secondary resistance with a multimeter and compare to spec. If out of range, replace coil.
Use a spark tester or ignition oscilloscope probe on the secondary to confirm spark presence and waveform quality at crank and under load.
Inspect and test connector continuity, pin fit, and harness for shorts to ground or open circuits. Repair or replace damaged wiring or connectors.
Verify proper battery voltage and engine ground integrity while testing; poor supply/ground can mimic coil faults.
If coil and wiring check good, consider an ECM/ignition driver fault; perform module-specific checks, consult service manual and consider module replacement only after excluding hardware and wiring.
After repairs, clear codes and road-test the vehicle under the conditions that previously set the code. Re-scan to confirm the fault is resolved.

Likely causes

Worn or fouled spark plug or damaged boot allowing arcing
Defective ignition coil (internal secondary failure)
Loose, corroded or damaged connector/pin at the coil
Carbon tracking or contamination on coil/boot
High-voltage lead or coil-to-plug wiring damaged

Fault status

⚠️ Status

Ignition Coil I secondary circuit malfunction detected. MIL illuminated. Possible misfire or weak/no spark from coil I. Inspect coil, plug, boot, wiring and related components.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-3 hours