Description & Operation
The camshaft position sensor (along with the crankshaft position sensor) provides inputs to the PCM to determine fuel injection synchronization and cylinder identification. From these inputs, the PCM determines crankshaft position.
The camshaft position sensor provides cylinder identification to the Powertrain Control Module (PCM). The sensor generates pulses as groups of notches on the camshaft sprocket pass underneath it. The PCM keeps track of crankshaft rotation and identifies each cylinder by the pulses generated by the notches on the camshaft sprocket. Four crankshaft pulses follow each group of camshaft pulses. The 3.0L engine is equipped with a camshaft driven mechanical distributor, which is equipped with an internal camshaft position (fuel sync) sensor.
On the 2.4L engine, the camshaft position sensor mounts to the rear of the cylinder head. The sensor also serves as a thrust plate to control endplay of the camshaft.
On 3.3L and 3.8L engines, the camshaft position sensor mounts to the top of the timing case cover, in which the bottom of the sensor is positioned above the camshaft sprocket.
When the PCM receives 2 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 3 pulses indicates cylinder 5. The 2 camshaft pulses which occur after cylinder No. 5 will signal cylinder No. 6. The PCM can synchronize on cylinders No. 1 or No. 4.
When metal aligns with the sensor, voltage goes low (less than 0.3 volts). When a notch aligns with the sensor, voltage switches 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 will determine the amount of pulses. If available, an oscilloscope can display the square wave patterns of each timing event.
Top Dead Center (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. The arrows and cylinder call outs represent which cylinder the flat spot and notches identify, they do not indicate TDC position.
The PCM determines fuel injection synchronization and cylinder identification from inputs provided by the camshaft position sensor and crankshaft position sensor. From the two inputs, the PCM determines crankshaft position.
The sensor generates pulses as groups of notches on the camshaft sprocket pass underneath it. The PCM keeps track of crankshaft rotation and identifies each cylinder by the pulses generated by the notches on the camshaft sprocket. Four crankshaft pulses follow each group of camshaft pulses.
The distance between the bottom of sensor and the camshaft sprocket is critical to the operation of the system.
To test this sensor, you will need the use of an oscilloscope. Visually check the connector, making sure it is attached properly and that all of the terminals are straight, tight and free of corrosion. The output voltage of a properly operating camshaft position sensor switches from high (5.0 volts) to low (0.3 volts). By connecting an oscilloscope to the sensor output circuit, you can view the square wave pattern produced by the voltage swing.