Neon R/T L4-2.0L VIN F HO (2001)
If available, an oscilloscope can display the square wave patterns of each voltage pulses. From the width of the output voltage pulses, the PCM calculates
engine speed. The width of the pulses represent the amount of time the output voltage stays high before switching back to low. The period of time the
sensor output voltage stays high before switching back to low is referred to as pulse width. The faster the engine is operating, the smaller the pulse width
on the oscilloscope.
By counting the pulses and referencing the pulse from the 60 degree signature notch, the PCM calculates crankshaft angle (position). In each group of
timing reference notches, the first notch represents 69 degrees before top dead center (BTDC). The second notch represents 49 degrees BTDC. The
third notch represents 29 degrees. The last notch in each set represents 9 degrees before top dead center (TDC).
The timing reference notches are machined at 20° increments. From the voltage pulse width the PCM tells the difference between the timing reference
notches and the 60 degree signature notch. The 60 degree signature notch produces a longer pulse width than the smaller timing reference notches. If the
camshaft position sensor input switches from high to low when the 60 degree signature notch passes under the crankshaft position sensor, the PCM
knows cylinder number one is the next cylinder at TDC.
