Ignition Coils and Ignition Control Module (ICM)

Ignition Coils And Ignition Control (IC) Module:

Three dual tower ignition coils (2) are mounted to the IC module (3), and are serviced individually. The IC module performs the following functions:
^ The IC module supplies a power and low reference circuit to the CMP and CKP sensors.
^ The IC module receives and processes the signals generated by the CMP and CKP sensors.
^ The IC module determines the correct coil triggering sequence, based on how many 18x ON-OFF pulses occur during a sync pulse. This coil sequencing occurs at start-up, and is remembered by the IC module. After the engine is running, the module will continue to trigger the coils without the CKP input.
^ The IC module determines the correct direction of the crankshaft rotation, and cuts spark and fuel delivery to prevent damage from backfiring if reverse rotation is detected.
^ The IC module sends 18x and 3x reference signals to the PCM.

The 3x reference signal is also known as the low resolution engine speed signal. This signal is generated by the IC module using an internal divide-by-six circuit. This circuit divides the 1 8x signal pulses by six. This divider circuit will not begin operation without a sync pulse present at start-up, and without 18x and 3x reference signals no fuel injection will occur.