Ignition Control Module: Description and Operation

Ignition Circuit:

The igniter performs the same function as the breaker points and condenser did in older standard type ignition systems. Located in the engine compartment near the coil, the igniter contains a transistorized switching device that interrupts the ignition coil primary current to fire the coil.

The igniter is switched "ON" and "OFF" by signals from the ECU. The ECU monitors operating conditions through various engine sensors, including a TDC sensor and engine speed/crankshaft position sensor in the distributor, and uses this information to regulate ignition timing according to pre-programmed values in the ECU memory.

When the atmospheric pressure sensor detects high altitude (above 1000 meters, 3280 feet), the ECU advances timing to compensate for loss of intake air volume and the consequential loss of compression pressure.