Crankshaft Position Sensor: Description and Operation

�9ICrank Angle Sensor Circuit:

CRANKSHAFT POSITION SENSOR

�~ICamshaft Position (TDC) Sensor Circuit:

CAMSHAFT POSITION SENSOR

Photoelectric Signal Pattern:

PURPOSE
The Control Unit uses the signal from these sensors to determine the fuel injection pulse width, ignition timing, and the intake air flow rate for each revolution of the engine.

OPERATION
Both sensors are incorporated into one disc and pick-up unit.
- The disc is affixed to the distributor shaft and the light-transmitting unit is mounted stationary to the distributor housing.

Crank Angle And #1 TDC Sensor:

The disc has 4 large slits in its circumference to indicate the crankshaft angle.
- An additional slit--located inward from the edge--is used to indicate number one cylinder top dead center position.

The pick-up uses two luminous diodes and two photo diodes to detect the two types of slits.
The disc rotates in a narrow gap between the luminous diodes and the photo diodes.

As the distributor shaft rotates, the slits pass between the sets of diodes.
- The light emitted from the luminous diodes passes through the slits to the photo sensing diodes.
- When the photo diodes detect light, they become conductive and generate a signal, which is sent to the Control Unit.

The Control Unit bases the sequence of the fuel injector firing on the signal generated when the single inner slit passes between the inner diode pair.

The slits at the outer circumference of the disc represent the exhaust stroke and detect the position of the crankshaft (and, therefore, the piston) relative to top dead center.