Modern vehicles rely on complex networks of sensors, actuators, and communication buses. Digital multimeters (DMMs) are too slow to catch intermittent faults. They display an average voltage reading rather than the actual signal.

In the past, waveform interpretation was passed down by senior technicians. "This ramp-up should look like a ski slope, not a staircase." Without a visual reference, new techs flounder.

Look closely at the trailing slope after the spike or during the switch-off phase. A tiny dip or "hump" reveals the physical movement of the injector valve closing. If the hump is missing, the injector is mechanically stuck. Ignition Primary and Secondary Systems Ignition diagnostics require isolating the spark phases.

The period where the transistor turns on, pulling the voltage to ground to charge the coil.