Ignition Coil Secondary
2021 Hyundai Tucson · 2.5L I4
Sensor Type
inductive
Waveform Type
dc-variable
Location
Secondary circuit between coil-on-plug unit and spark plug, accessed via capacitive pickup or secondary adapter
Pins
Unknown
Idle Frequency
20 Hz
Timebase
5ms/div
Voltage Scale
5kV/div
Trigger
5kV, rising edge
Wiring
N/A - measured using capacitive pickup clamp or piercing adapter on coil boot
Expected Voltage Range
At Idle
-2000V to 25000V
At Higher RPM
-2000V to 35000V
Expected Pattern
Sharp rise to firing voltage (15-25kV), followed by spark line at 2-4kV for 1-2ms, ending with oscillations
Known-Good Waveform
Initial firing spike of 15-25kV at idle with fresh plugs, followed by horizontal spark line at 2-4kV lasting 1.5-2ms. Spark line should be relatively flat with minimal slope. After spark extinction, expect 4-6 coil oscillations decaying to baseline. All cylinders should show firing voltage within 3kV of each other.
Common Failure Patterns
Firing voltage above 30kV at idle, steep upward-sloping spark line
Cause: Worn spark plugs with excessive gap or high resistance plug wires/boots
Short or absent spark line (less than 0.5ms), low firing voltage under 10kV
Cause: Fouled or carbon-tracked spark plug, shorted secondary winding
Diagnostic Tips
Hyundai Tucson 2.5L uses iridium plugs with service interval of 60,000 miles - verify replacement history. Common issue is oil seepage into plug wells from valve cover gasket causing coil boot tracking. Always inspect plug wells for oil contamination.
Related Diagnostic Trouble Codes
P0300P0301P0302P0303
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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