Electronic Ignition System

WARNING: This page is about a different car, the 1993 Toyota MR2. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: The electronic ignition system may be referred to as Electronic Spark Advance (ESA).

The electronic ignition system uses the Engine Control Module (ECM) for determining ignition timing (spark advance). The ECM determines ignition timing (spark advance) based on various input signals. Following input signals may be used: coolant temperature sensor, oxygen sensor, engine RPM, vehicle speed sensor, A/C switch, airflow meter, knock sensor, vacuum sensor and cranking (starter) signal. Input signals may vary on model application. Integrated (ignition coil on distributor) and remote ignition coil designs are used depending on model.

Crankshaft position and engine RPM input signals are delivered to the ECM by 2 pick-up coils in the distributor. Crankshaft position input signal is delivered to G, G+ or G1 (and G2 on some models) terminal of ECM, and engine RPM input signal is delivered to NE or NE+ terminal of ECM. See Fig 1.

On all models, ECM uses pick-up coil input signals to switch primary ignition circuit on and off. Primary circuit is turned off when ECM delivers a signal to ignitor on the IGT wire, causing ignition coil to fire the spark plug. After delivering a command to turn off primary circuit on the IGT wire, the ECM monitors IGF circuit to ensure primary switching occurred. See Fig 1.

Fig 1: Typical Electronic Ignition System Schematic