Camshaft Position Sensor: Description and Operation

Fig. 4 Camshaft Position Sensor (CMP) Location:

The three-wire Camshaft Position Sensor (CMP) is located below the fuel injection pump. It is attached to the back of the timing gear cover housing.

The Camshaft Position Sensor (CMP) performs multiple functions. One function is to detect engine speed (rpm). Another function is to relate crankshaft position and Top Dead Center (TDC) of the number 1 cylinder. Because the CMP is now used to relate crankshaft position, the Crankshaft Position Sensor (CKP) is no longer used.

Fig. 6 Camshaft Position Sensor (CMP):

The CMP contains a hall effect device called a sync signal generator to generate a sync signal.

The CMP uses three wires (circuits) for operation. One wire supplies a 5-volt signal from the Engine Control Module (ECM). Another wire supplies a sensor ground. The third wire supplies a signal back to the ECM relating engine speed and crankshaft position.

Fig. 7 Notches At Rear Of Camshaft Drive Gear:

The sensor detects machined notches on the rear face of the camshaft drive gear to sense engine speed.

The CMP also detects an area on the camshaft drive gear that has no notch. When the sensor passes this area, it tells the Engine Control Module (ECM) that Top Dead Center (TDC) of the number 1 cylinder is occurring. The ECM will then adjust fuel timing accordingly

As the tip of the sensor passes the notches, the interruption of magnetic field causes voltage changes from 5 volts to 0 volts.