DISTRIBUTORLESS Ignition System: Notes

Depending on number of cylinders, ignition system is a 2-coil or 3-coil, distributorless ignition system. PCM controls timing and directly activates each power transistor to fire coils. On 4-cylinder engines, power transistor "A" controls primary current of ignition coil "A" to fire spark plugs on cylinders No. 1 and 4 at same time. Power transistor "B" controls primary current of ignition coil "B" to fire spark plugs on cylinders No. 2 and No. 3 at same time. On V6 engines, companion cylinders No. 1 and 4, 2 and 5, and 3 and 6 are fired together.

PCM uses signals from CMP sensor to determine which coil to fire. PCM uses signals from CKP sensor to adjust timing. Additional inputs from VAF sensor, IAT sensor, BARO sensor, ECT sensor, closed Throttle Position (TP) sensor, ignition switch, PNP switch (automatic transmissions), Knock Sensor (KS) and VSS are used by PCM to optimize timing for operating conditions. When engine is cold or operated at high altitudes, PCM will advance timing.