Modern cars have the camshaft and crankshaft sensors performing the same duties as did the distributor in old model cars. It’s a method used to know the exact position of the number 1 cylinder in respect to top dead center on the compression stroke.
These two sensors are most often a Hall Effect or magnetic reluctant controlled component. The Hall Effect sensor type uses a notched ring and an electromagnetic sensor. The sensor is positioned in one place while the notched ring, also called an interrupter, passes through it.
Passing the notches on the wheel through the sensor creates a signal that is then forwarded to the Power train Control Module (PCM) indicating the position of the crankshaft or camshaft relative to top dead center on the number 1 cylinder.
The magnetic reluctant sensor makes use of a rare earth magnet and a winding of wire. As the trigger wheel passes near the sensor it creates an AC voltage signal, which is then sent to the PCM.
The era of the crank and cam sensors aided reduce the difference in ignition timing signals that is so common in a distributor controlled ignition engine.
PLACEMENT OF THE CAMSHAFT SENSOR
Placement of the camshaft sensor is dependent on the type of engine, namely an overhead camshaft or conventional, centrally located camshaft as used with push rod controlled valves.
Generally, engines with the camshaft in the center of the block will often times place the cam sensor in the front above the timing chain cover or in the rear top of the engine. It is sometimes located in an hole that was previously used for the distributor.
However, overhead cam engines will often have the cam sensor at the rear of the camshaft. Some engines will have the sensor at the valve cover or even in the front of the camshaft.
FUNCTION OF THE CAMSHAFT SENSOR
The camshaft sensor indicates to the PCM of the camshaft position relative to the crankshaft.
By this act of monitoring the camshaft position, the PCM remains in the know of the timing of the opening and closing of the intake valves.
By always checking the camshaft sensor and comparing it with the crankshaft sensor, the PCM is able to know when each cylinder is reaching the top dead center and where the valves are positioned.
Vehicle Ignition and fuel injector timing relies on this vital information especially with sequential fuel injection. Sequential fuel injection fires individual injectors at a specific point in the cylinder’s compression stroke.
The cam sensor in conjunction with the crank sensor also informs the PCM to determine which cylinder is on its compression stroke.
SECONDARY CAM SENSOR FUNCTIONS
The crankshaft sensor also serves as to detect cylinder misfires.
When the PCM senses sufficient variances or difference in crankshaft speed, it sees this as an indication of a misfire. The computer then sets a misfire code and turns on the check engine light when the misfires become too often. The code will show which cylinder is misfiring
SEE ALSOHOW TO REPLACE A TIMING BELT