For 1990-2009 cars

The EI systems on the 3400 (LA1) engine uses a coil pack with one ignition coil for every two cylinders in the engine. Mounted under the ignition coils on each system is an ignition control module (ICM) that performs ignition coil switching functions and interacts with the powertrain control module (PCM) to optimize ignition system operation.

On these engine systems, the spark timing is controlled electronically. The ICM controls the spark timing during engine start-up, and provides a back-up timing system that will allow the engine to run in the event of an open or ground in the ignition control (IC) circuit. Once the engine starts and is running above approximately 400 RPM, the PCM takes over the spark timing and sends signals to the ICM for ignition coil switching.

For more information on diagnosing and servicing Electronic Ignition System, refer to Engine Controls.