Ignition Coil Primary
2012 Jeep Wrangler · 3.6L V6
Sensor Type
inductive
Waveform Type
pulse-width
Location
Individual coil-on-plug assemblies mounted directly on each spark plug, valve cover top
Pins
2-pin connector
Idle Frequency
16.67 Hz
Timebase
10ms/div
Voltage Scale
100V/div
Trigger
50V, rising edge
Wiring
Black/Gray (ground/switching) and Pink/Yellow (12V power feed from ASD relay)
Expected Voltage Range
At Idle
0V to 400V
At Higher RPM
0V to 450V
Expected Pattern
Square wave with initial 12V dwell period, sharp drop to near 0V when PCM grounds circuit, followed by inductive spike to 300-400V when coil fires
Known-Good Waveform
Primary waveform should show clean 12V dwell period of 2-4ms at idle, followed by sharp turn-off and inductive kickback spike to 300-400V lasting approximately 1ms. The limiting voltage should be consistent across all six cylinders, and the current ramp during dwell should be smooth without oscillations.
Common Failure Patterns
Inductive spike below 250V or erratic spike height
Cause: Weak coil windings or internal breakdown in coil pack
No dwell period or constant 12V
Cause: Open PCM driver circuit or broken ground wire to coil
Diagnostic Tips
The 3.6L Pentastar uses individual coil drivers in the PCM; compare all six coil primary patterns simultaneously to identify weak coils. Jeep TSB 18-010-18 addresses coil-related misfires on cylinders 2, 4, and 6 due to heat exposure.
Related Diagnostic Trouble Codes
P0351P0352P0353P0354
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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