The 1995-98 Mazda Millenia S with the 2.3L Miller-cycle supercharged engine and the 1998 2.0L and 2.5L engines use a distributorless ignition system.
The 2.3L engine utilizes an individual coil for each spark plug. Which means it has six separate coils which are all controlled by the engine computer.
The 1998 2.0L and 2.5L (except Millenia) engines utilize a coil pack, with 4 or 6 terminals on it. The system is known as a waste spark system since two plug wires are fired at the same time; one for a cylinder on compression, the other for a cylinder on exhaust.
The ECU sends the spark timing signal through the ignition module in the coil based on its triggering signal from various sensors and switches. The sensors and switches include the following:
The CranKshaft Position (CKP) sensor provides a signal to the ECU to indicate crankshaft Top Dead Center (TDC). The CaMshaft Position (CMP) sensor provides a signal to the ECU to indicate whether the engine is at TDC compression, or TDC exhaust.
Both systems operate in the same manner. The power relay closes and changes the coil primary windings when the ignition switch is turned ON . When the engine is running, each ignition module grounds the negative side of its coil primary circuit which induces spark. This results in an inductive charge built up in the secondary circuit. The spark is then sent directly to the spark plug that the coil assembly rests on top of (2.3L engines) or through the spark plug wire connected to that coil pack (1998 2.0L and 2.5L engines).
Other non-electronic components in the system include the starter interlock switch, battery and spark plugs.