Ignition Coil Secondary
2019 Jeep Wrangler · 3.6L V6
Sensor Type
inductive
Waveform Type
pulse-width
Location
Secondary circuit measured from coil tower to spark plug, coil-on-plug configuration on each cylinder
Pins
Unknown
Idle Frequency
16.67 Hz
Timebase
5ms/div
Voltage Scale
5kV/div
Trigger
5kV, rising edge
Wiring
N/A - measured via capacitive pickup or spark plug wire adapter on coil boot
Expected Voltage Range
At Idle
-2000V to 35000V
At Higher RPM
-2000V to 45000V
Expected Pattern
Sharp firing spike to 8-15kV, immediate drop to spark line at 2-5kV maintained for 1.0-1.5ms, followed by coil oscillations and spark plug capacitance discharge
Known-Good Waveform
Firing spike should reach 8-15kV at idle with light load, dropping immediately to a flat spark line at 2-5kV that maintains steady voltage for 1.0-1.5ms burn time. After spark extinction, expect 3-5 clean coil oscillations at decreasing amplitude followed by a small negative spike from plug capacitance. The Pentastar's lean burn strategy may show slightly higher firing voltages under certain conditions.
Common Failure Patterns
Firing line exceeds 20kV with short burn time under 0.8ms and irregular spark line voltage
Cause: Excessive spark plug gap due to electrode wear, plug fouling from oil consumption common on 2018-2020 models, or high resistance in coil boot
Spark line shows upward slope or voltage increasing during burn time, shortened burn duration
Cause: Lean air-fuel mixture, vacuum leak, or failing fuel injector specific to that cylinder
Diagnostic Tips
Inspect coil boots carefully for carbon tracking and oil contamination from valve cover leaks. The 3.6L is known for oil consumption on earlier production years which fouls plugs. Use Mopar-specified plugs only as aftermarket plugs often cause misfires on this engine.
Related Diagnostic Trouble Codes
P0300P0301P0302P0303
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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