The electronic ignition (EI) system provides a spark to ignite the compressed air/fuel mixture at the correct time in order to control fuel combustion. The PCM controls the system's spark advance which provides optimum engine performance, better fuel economy, and emissions control.

The EI system has several advantages over a mechanical distributor system:

The EI system does not use the conventional distributor and coil. The EI system consist of the following components:

Conventional ignition coils have one end of the secondary winding connected to the engine ground. In this EI system, neither end is grounded. Instead, each end of a coil's secondary winding is attached to a spark plug. Each cylinder is paired with the one opposite, known as COMPANION cylinders.

The spark plugs on the COMPANION cylinders fire at the same time when the coil discharges. This completes the series circuit. The cylinder on compression is said to be the EVENT cylinder; the one on exhaust is the WASTE cylinder.

The WASTE cylinder requires very little of the available energy to fire the plug. The EVENT cylinder requires the remaining energy. The same process occurs when the cylinders reverse roles. This method of ignition is called a WASTE SPARK ignition system.

The polarity of the ignition coil primary and secondary windings is fixed. Thus, one spark plug always fires with a forward current flow while the COMPANION plug fires with a reverse current flow. Conversely, the distributor ignition (DI) system fires all of the plugs with the same direction of current flow. Since 30 percent more voltage is needed in order to fire a spark plug backward, the ignition coil design is improved, with saturation time and primary current flow increased. The EI system design allows higher available ignition coil secondary voltage, more than 40,000 V at any engine rpm.The polarity and the cylinder pressure determine the required spark plug voltage.

It is possible for one spark plug to fire even if a plug wire from the ignition coil is disconnected from the COMPANION plug. The disconnected plug wire acts as one plate of a capacitor, with the engine acting as the other plate. These two PLATES are charged as a spark jumps across the gap of the connected spark plug. The PLATES are then discharged as the secondary energy is dissipated in an oscillating current across the gap of the still-connected plug.

Secondary voltage requirements are very high with a disconnected plug. The coil has enough reserve energy in order to fire the disconnected plug at idle, but may fail at higher loads, where both of the COMPANION plugs may misfire.