In Model Year 1998, the 2RZ-FE engine transitioned from distributor ignition to a distributorless system. The 2RZ-FE and 3RZ-FE engines have no distributor, but are equipped with two dual-terminal coils. When signaled by the on-board computer, the coils fire in sequence and distribute the spark through conventional spark plug cables.
The 5VZ-FE engines are equipped with what is called the Toyota Direct Ignition (TDI). This system improves the timing accuracy and enhances the overall reliability of the ignition system. The TDI uses a two-cylinder simultaneous (waste spark) ignition system which fires two cylinders at the same time with one coil. In a waste spark system, one spark plug is attached to each end of the secondary coil winding. This circuit arrangement causes one of the plugs in each cylinder pair to fire in a forward direction, and the other to fire in a reverse direction. The cylinder on the compression stroke is defined as the 'event' cylinder, while the cylinder in the exhaust stroke is called the 'waste' cylinder. The coils are positioned over one bank of the plugs. This arrangement has eliminated half of the normal required plug wires.
The 2UZ-FE engine use an arrangement where each spark plug has its own coil. There are no spark plug wires.