Ignition Coil Primary
2019 Jeep Wrangler · 3.6L V6
Sensor Type
inductive
Waveform Type
pulse-width
Location
Individual coil-on-plug units mounted directly on each spark plug, valve cover mounted on each cylinder bank
Pins
2-pin connector
Idle Frequency
16.67 Hz
Timebase
10ms/div
Voltage Scale
100V/div
Trigger
50V, rising edge
Wiring
Gray/Black (switched 12V power feed), Black/Light Blue (PCM ground switching control)
Expected Voltage Range
At Idle
0V to 350V
At Higher RPM
0V to 400V
Expected Pattern
Square wave with sharp rise to battery voltage, flat dwell period (2-4ms at idle), then sharp spike to 350-400V during coil collapse, followed by oscillating decay
Known-Good Waveform
Primary waveform should show clean 12-14V dwell time of 2.5-4ms at idle, followed by inductive spike reaching 350-400V peak during coil collapse. The spike should be sharp and clean with 3-5 oscillations dampening rapidly, indicating proper coil saturation and healthy primary windings with approximately 0.5-0.7 ohms resistance.
Common Failure Patterns
Primary spike only reaches 150-200V with extended oscillation period and irregular amplitude
Cause: Shorted primary windings in coil or degraded coil insulation, common on high-mileage 3.6L Pentastar engines
Dwell time extends beyond 5ms with reduced or absent inductive spike
Cause: PCM driver circuit failure or corroded connector at coil, moisture intrusion common in Wrangler off-road use
Diagnostic Tips
The 3.6L Pentastar is sensitive to oil quality affecting VVT operation which can cause timing-related misfire. Always verify cam/crank correlation before condemning coils. Check for oil contamination in coil boots as valve cover gasket leaks are common and cause coil failure.
Related Diagnostic Trouble Codes
P0351P0352P0353P0354
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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