See Figures 1 and 2
Only the 1MZ-FE engine uses a distributorless ignition.
The Engine Control Module (ECM) is programmed with data for optimum ignition timing under all operating conditions. Using data provided by sensors which monitor various engine functions (RPM, intake air volume, engine temperature, etc.) the ECM triggers the spark at precisely the right instant.
The ECM monitors the engine condition signals from each sensor, calculates the ignition timing and sends an ignition signal to the igniter. High voltage from the ignition is distributed to each spark plug in the appropriate order to generate a spark between the electrodes, which ignites the air fuel mixture.
The igniter interrupts the primary current with the ignition signal (IGT signal) from the ECM and generates sparks at the spark plug. Also, as a fail-safe measure, when ignition occurs an ignition confirms signal (IGF signal) is sent to the ECM.
The ignition coil uses a closed core coil with the primary coil wrapped around the core and the secondary coil wrapped around the primary coil. This allows the generation of a high voltage sufficient to cause a spark to jump across the spark plug gap. The camshaft position sensor detects the camshaft position and the crankshaft position sensor detects the crankshaft position.
To maintain the most appropriate ignition timing, the ECM sends a control signal so that the igniter will pass the current to the ignition coils and spark plugs to produce a spark.