Ignition Timing Control: Notes

A microcomputer in the PCM controls ignition timing according to engine speed and vacuum within the intake manifold. Engine speed and vacuum are transmitted to PCM by signals from Crankshaft Position (CKP) sensor, Cylinder Position (CYP) sensor, TDC sensor, Throttle Position (TP) sensor, Engine Coolant Temperature (ECT) sensor, knock sensor(s), MAF sensor, and MAP sensor.

The PCM calculates ignition timing for each engine speed, manifold pressure, and coolant temperature. When these conditions have been processed, the PCM sends signals to the Ignition Control Module (ICM) to trigger coil(s).