Camshaft Position Sensor: Description and Operation

Camshaft Sensor:

PURPOSE
- Sensor provides PCM with cylinder identification.
- PCM uses sensor input to determine fuel injection sequence and ignition timing.

OPERATION
Sensor generates pulses as groups of notches on the camshaft sprocket pass underneath it.
- When metal aligns with the sensor, voltage goes low (less than 0.3 volts).
- When a notch aligns with the sensor, voltage spikes high (5.0 volts).
- As a group of notches pass under the sensor, the voltage switches from low (metal) to high (notch) then back to low.
- The number of notches determine the amount of pulses.

NOTE: If available, an oscilloscope can display the square wave patterns of each timing event.

NOTE: The arrows and cylinder call outs on the following image represent which cylinder the flat spot and notches identify, they do not indicate Top Dead Center (TDC) position.

Camshaft Sprocket:

- When the PCM receives two cam pulses followed by the long flat spot on the camshaft sprocket, it knows that the crankshaft timing marks for cylinder # 1 are next (on driveplate).
- When the PCM receives one camshaft pulse after the long flat spot on the sprocket, cylinder number # 2 crankshaft timing marks are next.
- After 3 camshaft pulses, the PCM knows cylinder # 4 crankshaft timing marks follow.
- One camshaft pulse after the three pulses indicates cylinder # 5.
- The two camshaft pulses after cylinder 5 signals cylinder # 6.
- The PCM can synchronize on cylinders 1 or 4.

NOTE: TDC does not occur when notches on the camshaft sprocket pass below the cylinder. TDC occurs after the camshaft pulse (or pulses) and after the 4 crankshaft pulses associated with the particular cylinder.

NOTE: The distance between the sensor and camshaft sprocket is critical to system operation. Be sure paper spacer is attached to sensor face when installing sensor. SEE Powertrain Management/Computers and Control Systems/Camshaft Position Sensor/Service and Repair.