Ignition Coil Secondary
2021 Toyota RAV4 · 2.5L I4
Sensor Type
inductive
Waveform Type
pulse-width
Location
Coil-on-plug secondary circuit between coil and spark plug, measure using capacitive pickup or secondary probe
Pins
Unknown
Idle Frequency
20 Hz
Timebase
2ms/div
Voltage Scale
5kV/div
Trigger
2kV, rising edge
Wiring
N/A - internal coil winding to spark plug terminal
Expected Voltage Range
At Idle
0V to 35000V
At Higher RPM
0V to 40000V
Expected Pattern
Sharp firing spike to 8-15kV, immediate drop to spark line at 2-4kV for 1-2ms burn time, followed by coil oscillations dampening to zero
Known-Good Waveform
Firing line should show sharp vertical spike reaching 8-15kV under normal load at idle, dropping immediately to a relatively flat spark line at 2-4kV lasting 1-2ms. After spark extinction, coil oscillations should show 3-6 diminishing waves. All four cylinders should show similar firing voltages within 3kV of each other.
Common Failure Patterns
Firing line above 20kV with extended spark line duration or upward sloping spark line
Cause: Excessive spark plug gap wear, lean air-fuel mixture, or increased cylinder compression resistance
Firing line below 5kV with shortened or absent spark line
Cause: Fouled spark plug, carbon tracking in coil boot, or failed coil secondary winding
Diagnostic Tips
Toyota A25A-FKS engine uses iridium plugs with extended service intervals. Coil boot deterioration is common after 100k miles causing intermittent misfires that worsen in wet conditions. Use parade pattern to compare all cylinders simultaneously.
Related Diagnostic Trouble Codes
P0300P0301P0302P0303
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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