Ignition Coil Secondary
2012 Jeep Wrangler · 3.6L V6
Sensor Type
inductive
Waveform Type
pulse-width
Location
Measured at spark plug wire terminal on coil-on-plug assembly, cylinders 1-6
Pins
1-pin connector
Idle Frequency
16.67 Hz
Timebase
5ms/div
Voltage Scale
5kV/div
Trigger
5kV, rising edge
Wiring
N/A - measured via capacitive pickup or plug wire adapter
Expected Voltage Range
At Idle
-5000V to 35000V
At Higher RPM
-8000V to 40000V
Expected Pattern
Sharp firing spike to 8-15kV, followed by spark duration at 1.5-3kV for 1-1.5ms, then coil oscillations damping to zero
Known-Good Waveform
Secondary pattern should show initial firing line of 8-15kV at idle with lean mixtures potentially requiring up to 18kV. Spark duration should be 1-1.5ms with burn voltage around 1.5-3kV, followed by 3-5 coil oscillations damping smoothly. All six cylinders should show firing voltage within 3kV of each other.
Common Failure Patterns
Firing line exceeds 20kV with short spark duration
Cause: Excessive spark plug gap, carbon tracking in coil boot, or worn spark plugs
Firing line below 5kV with erratic spark line
Cause: Fouled spark plug, cracked coil boot allowing corona discharge, or low cylinder compression
Diagnostic Tips
Use a secondary ignition adapter rated for 40kV+ on COP systems. Chrysler specifies Champion RC12YC or equivalent spark plugs gapped at 0.043 inches; incorrect gap is a common cause of high firing voltage and coil failure on these engines.
Related Diagnostic Trouble Codes
P0300P0301P0302P0303
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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