Camshaft Position Sensor: Description and Operation

Distributor:

Two Camshaft Position Sensors (CMP) are used. CMP1 detects when number one cylinder is at top dead center. CMP2 sends a signal for each 1/4 camshaft revolution. This information is sent to the Powertrain Control Module (PCM), where it is used to control fuel injection timing.

A single slotted disc is used for both sensors. As the distributor spins, a window in the disc allows light from a Light Emitting Diode (LED) to pass to a phototransistor, signaling the position of the camshaft. The disc has two rings of slots. The outer ring (CMP2) has four short slots, and the inner ring (CMP1) has one longer slot.