Crank & Cam Trigger Signals: Diagnose Before You Tune
If the ECU cannot trust engine position, no amount of fuel or ignition-table work can make the calibration reliable.
Position is the ECU's clock
Crank and cam sensors tell the ECU engine speed, angle and cycle. Injection timing, ignition timing, dwell and many safety strategies depend on that reference. A missing tooth, incorrect polarity or intermittent edge can appear as a misfire, sync loss, hard starting or an engine that simply will not rev cleanly.
Capture the signal under real conditions
A multimeter can confirm supply voltage, but it cannot show waveform shape. The useful test is a scope capture while cranking and, when safe, through the problem rpm range. Look for consistent amplitude, clean edges, correct tooth count and stable phase between crank and cam.
Fix the cause, then set thresholds
Filtering and arming thresholds are useful, but they should not hide a poor sensor gap, damaged reluctor, weak ground or badly routed cable. Mechanical alignment and wiring integrity come first. ECU settings should then be matched to a verified waveform, with a final timing-light check before load is applied.
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