Seville STS V8-4.6L VIN 9 (1998)
Position Sensor Signals
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The Crankshaft Reluctor Ring has 24 evenly spaced notches plus 8 additional notches (shaded) used for synchronization.
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As the crankshaft rotates, the notches pass the position sensors and create a voltage pulse signal in the sensor that is an input for the Ignition
Control (IC) module.
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Because of the physical location of the two crankshaft position sensors, the signal of "B" lags the signal of "A" by 27 degrees of crankshaft
revolution.
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To synchronize the ignition, the IC module first counts the number of "B" pulses between every 2 "A" pulses. There can be 0,1 or 2 "B" pulses
between "A" pulses.
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When the IC module sees 0 "B" pulses between "A" pulses, it starts counting "B" pulses between "A pulses. When the IC module counts
exactly 4, it synchronizes the ignition on the very next "A" pulse. If the IC module counts over 4 (jumps from 3 to 5), it waits for another "B"
pulse between "A" pulse to start counting again.
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This process allows the ignition to synchronize and fire the 1st spark plug within 180 degrees (1/2 engine revolution).
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The camshaft position sensor provides the IC module with cylinder #1 firing order information, which the PCM uses for sequential fuel
injection.
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Using 3 sensors allows the IC module to maintain ignition synchronization even if one of the 3 sensors fails.
