Every edge on a crank or cam signal tells the ECU where the engine is. A spike from an ignition coil, an alternator or a badly routed wire can produce a brief pulse that looks like a real edge. Count it as a tooth and the ECU's position math is wrong, which shows up as sync loss, trigger errors, misfires or a sudden cut.
The Trigger Glitch Filter sets a minimum time, in microseconds, that a signal must stay in its new state before the ECU accepts it as a real transition. Anything that flips and flips back quicker than that is treated as a glitch and ignored.
Setting it up
The table can be expanded to 8x1, and it's best mapped against Engine RPM. That matters because real teeth get shorter as the engine speeds up. A filter time that comfortably rejects noise at cranking speed could start eating genuine teeth at high RPM.
| If the value is… | What happens |
|---|---|
| Too small | Noise pulses get through and are counted as teeth |
| Too large | Real, short pulses are rejected, usually at high RPM |
Our approach: use the ECU oscilloscope to see how long the real pulses are across the RPM range, and keep the filter well below the shortest of them. If you're raising the filter to hide noise, also fix the source: shielding, grounds and routing trigger wires away from ignition leads. See trigger setup and trigger arming voltage for the related settings.
