See Figure 1
The Electronic Spark Advance (ESA) system is used on all Toyota Previas. The electronic ignition system offers many advantages over the conventional breaker points ignition system. By eliminating the points, maintenance requirements are greatly reduced. An electronic ignition system is capable of producing a much higher voltage which in turn aide in starting, reduces spark fouling and provides emission control.
The ESA ignition system consists of a distributor with a signal generator, ignition coil (s), electronic igniter and a micro-computer called an Electronic Control Module (ECM). The 2TZ-FZE engine also uses a Crankshaft Position (CKP) sensor. The ECM is programmed with data for optimum ignition timing for a wide range of driving and operating conditions. Using data provided by the various engine mounting sensors (intake air volume, engine temperature, rpm, etc.), the ECM converts the data into a reference voltage signal and sends this signal to the igniter mounted inside the distributor. The signal generator receives a reference voltage from the ECM and activates the components of the igniter. The signal generator consists of three main components: the signal rotor, pick-up coil and the permanent magnet. The signal rotor revolves with the distributor shaft, while the pick-up coil and permanent magnet are stationary. as the signal; rotor spins the teeth on it pass a projection leading from the pick-up coil. When this occurs, voltage is allowed to flow through the system and fire the spark plugs. This process happens without physical contact or electrical arching; therefore, there is no need to replace burnt or worn parts.