Camshaft Position Sensor
The CMP sensor contains a Hall Effect device that provides cylinder identification to the Powertrain Control Module (PCM). On models with distributors, Camshaft Position Sensor (CMP) sensor is made up of a Hall Effect switch (sync signal generator) and a rotating pulse ring (shutter) located on the distributor shaft. See Fig 1 . On models with Distributorless Ignition System (DIS), CMP sensor reads slots in cam timing sprocket. See Fig 2 or Fig 3 . The sensor generates pulses as groups of notches on the camshaft sprocket pass underneath it. The PCM keeps track of crankshaft rotation and identifies each cylinder by the pulses generated by the notches on the camshaft sprocket. Crankshaft pulses follow each group of camshaft pulses. When metal aligns with the sensor, voltage goes low (less than 0.3 volt). When a notch aligns with the sensor, voltage spikes high (5.0 volts). As a group of notches pass under the sensor, the voltage switches from low (metal) to high (notch) then back to low. The number of notches determines the amount of pulses. If available, an oscilloscope or DRBIII(R) PEP Module can display the square wave patterns of each timing event. On all models, Powertrain Control Module (PCM) uses this information along with information from crankshaft position sensor to determine if fuel injectors and ignition coils are properly sequenced for correct cylinders.