1998 Chrysler Cirrus question about crank sensor

The crank sensor (AKA crankshaft position sensor) senses when a notch on the crankshaft goes by and sends a pulse to the car's computer. This tells the computer where the crankshaft is in it rotation so that the computer will fire the spark plug at the correct time. This also allows the computer to change the timing under different conditions such as if gas of too low an octane rating is being used causing predetonation (called knocking) which is sensed by the knock sensor.