Ignition Coil Primary
2021 Toyota Camry · 2.5L I4
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
20.83 Hz
Timebase
10ms/div
Voltage Scale
5V/div for primary side observation
Trigger
7V, falling edge
Wiring
IGT (ignition trigger) signal wire - typically gray or black/yellow stripe, and 12V power feed - typically pink or red/black stripe
Expected Voltage Range
At Idle
0V to 14V
At Higher RPM
0V to 14V
Expected Pattern
Sharp switching pattern with dwell time approximately 3-4ms, clean on-time at battery voltage, sharp drop to near 0V, followed by inductive spike to 250-350V on switching off
Known-Good Waveform
Clean square wave switching with dwell time of 3-4ms at idle. Primary voltage rises instantly to battery voltage when transistor closes, then drops sharply to 0V when coil fires with a brief inductive spike visible. Pattern repeats every 48ms at idle (4-cylinder firing). Current limiting should show flat top at battery voltage during dwell.
Common Failure Patterns
Dwell time extends beyond 5ms or shows irregular timing, inductive spike reduced or absent
Cause: Failing ignition coil with shorted windings or weak primary winding resistance
Diagnostic Tips
Toyota's 2.5L A25A-FKS engine uses individual coil drivers in the ECM. Check for oil contamination in spark plug wells which commonly damages coil assemblies. Verify 12V power supply at pink wire before condemning coil or ECM driver.
Related Diagnostic Trouble Codes
P0351P0352P0353P0354
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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