Cam Shaft Position Sensor (CMPS) is hall sensor type. Sensing the teeth attach at the end of cam shaft, CMPS detects rotation of Cam shaft. (1 signal per 1 rotation) As Cam shaft rotates once while Crank shaft does twice, CMPS reference point generates once while CKPS' do twice. As this signal inputted to ECM, it distinguishes crank angle and the cylinder which requires fuel injection in order to determine injection sequence and duration.