How do I check cam and crank sensor timing with a scope?

Short answer: Capture the crank and cam signals at the same time on two channels, then compare their alignment with a known-good waveform for the engine to see whether timing has jumped or the chain has stretched.

Crank and cam correlation codes often lead to timing chain or belt questions. A two-channel scope capture shows both signals together. Each engine has a specific relationship between crank teeth and cam edges, so a shift indicates the cam is out of position relative to the crank.

Back-probe both sensor signal wires and set a time base that shows at least one full engine cycle, which is two crank revolutions. Trigger on the cam signal for a stable display. Compare the capture with a known-good reference from a database, another identical engine or service information.

A consistent offset suggests mechanical timing changes, such as chain stretch or a jumped tooth. A varying relationship may indicate a cam phaser not returning to its parked position. Keep leads away from belts and the fan while cranking or running, and route them so they cannot fall into moving parts.

Last reviewed 2026-11-09 · Ignition and Engine Waveforms

General guidance only. Follow the vehicle and tool manufacturer's procedures, and confirm vehicle coverage on the tool maker's list before buying.