Spark

The scan tool displays -64 to +64 degrees. Displays the spark timing being commanded by the PCM on the IC circuit. A negative (-) value indicates degrees BTDC, or spark advance. A positive value indicates degrees After Top Dead Center (ATDC), or spark retard. Because the Ignition Control Module (ICM) sets spark advance at a fixed value of 10 degrees BTDC while operating in Bypass mode, the displayed Spark advance only reflects true spark timing when the PCM has commanded IC mode.