Camshaft Position Sensor: Description and Operation

CAMSHAFT POSITION SENSOR
The Camshaft Position Sensor (CMP) on this engine is located below the fuel injection pump. It is bolted to the back of the timing gear cover.

The Camshaft Position Sensor (CMP) contains a hall effect device. A rotating target wheel (tonewheel) for the CMP is located on the front timing gear. This hall effect device detects notches located on the tone-wheel. As the tonewheel rotates, the notches pass the tip of the CMP

When the leading edge of the tonewheel notch passes the tip of the CMP, the following occurs: The interruption of magnetic field causes the voltage to switch high resulting in a signal of approximately 5 volts.

When the trailing edge of the tonewheel notch passes the tip of the CMP, the following occurs: The change of the magnetic field causes the signal voltage to switch low to 0 volts.

Fig.10 5.9L Diesel CMP:

The CMP provides a signal to the Engine Control Module (ECM) at all times when the engine is running. The ECM uses the CMP information primarily on engine start-up. Once the engine is running, the ECM uses the CMP as a backup sensor for engine speed. The Crankshaft Position Sensor (CKP) is the primary engine speed indicator for the engine after the engine is running.