Spark

Scan Tool Range -64 degrees to 64 degrees. This displays the spark timing being commanded by the PCM on the IC circuit. A negative (-) value indicates degrees Before Top Dead Center (BTDC), or spark advance. A positive value indicates degrees After Top Dead Center (ATDC), or spark retard. Because the ignition control module sets spark advance at a fixed value of 10° BTDC while operating in Bypass mode, the displayed spark advance only reflects true spark timing when the PCM has commanded the IC mode.