Ignition Timing Control: Notes

A microcomputer inside PCM controls ignition timing according to engine speed and vacuum within 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 Sensors (KS), Mass Air Flow (MAF) sensor, and Manifold Absolute Pressure (MAP) sensor.

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