LSS V6-3.8L VIN K (1997)
Ignition Control Module: Description and Operation
PCM
The ignition control module performs the following functions:
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It powers the dual crankshaft position 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.
POWERTRAIN CONTROL MODULE
The PCM is responsible for maintaining proper spark and fuel injection timing for all driving conditions. Ignition Control (IC) spark timing is the PCM
method of controlling spark advance and ignition dwell. To provide optimum driveability and emissions, the PCM monitors input signals from the
following components in calculating Ignition Control (IC) spark timing:
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Ignition Control module (ICM).
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Engine Coolant Temperature (ECT) sensor.
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Intake Air Temperature (IAT) sensor.
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Mass Air Flow (MAF) sensor.
