Lumina V6-3.8L VIN K (1998)
Ignition Control Module: Description and Operation
DESCRIPTION
The ignition control module performs the following functions:
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It powers the dual Crankshaft Position (CKP) Sensor internal circuits.
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It supplies the voltage signals that each respective Hall effect switch pulses to ground to generate the CKP Sync and CKP 18X signal pulses.
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It determines the correct ignition coil firing sequence, based on how many CKP 18X signal transitions occur during a CKP Sync pulse. This coil
sequencing occurs at start-up. After the engine is running, the module remembers the sequence, and continues triggering the ignition coils in
proper sequence.
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It determines whether or not the crankshaft is rotating in the proper direction, and cuts off fuel delivery and spark to prevent backfiring if reverse
rotation is detected.
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It sends the 3X reference and 18X reference signals to the PCM. The PCM determines engine RPM from these signal. These signals used by the
PCM to determine crankshaft speed for Ignition Control (IC) spark advance calculations. The falling edge of each 3X reference and 18X reference
signal pulse occurs at a specific time in relation to top dead center of any cylinder stroke. The 3X reference signal sent to the PCM by the ignition
control module is an ON - OFF pulse occurring 3 times per crankshaft revolution. This is neither the CKP Sync pulse nor the 18X crankshaft
position sensor pulse, but both of these are required before the ignition control module will generate the 3X reference signal. The ignition control
module generates the 3X reference signal by an internal divide-by-6 circuit. This divider circuit divides the CKP 18X signal pulses by 6. The
divider circuit is enabled, or ready to begin dividing, only after it receives a crankshaft position sensor CKP Sync pulse. After beginning, the
divider circuit does not need the Sync pulses to continue operating. If either the CKP 18X or CKP Sync pulses are missing at start-up, the ignition
control module will not generate 3X reference or 18X reference signal pulses and no fuel injector pulses will occur.
