Ignition Timing Advance Control

Electronic Spark Timing (EST) is controlled by ECM. Ignition module sends a reference signal on Yellow/Red wire to ECM when engine is cranking. With engine speed less than 400 RPM, ignition module will control ignition timing.

When engine speed is greater than 400 RPM, ECM applies 5 volts on the by-pass line (Yellow/Green wire) to switch timing control to ECM (EST mode). In the EST mode, ECM controls the ignition timing.