Camshaft Position Sensor: Description and Operation

PURPOSE
The Camshaft Position Sensor supplies a signal to the Powertrain Control Module (PCM) when the #1 piston starts it's intake stroke. The PCM using this signal to syncronize the opeation of the Sequenial Fuel Injection system.

OPERATION
The camshaft sensor is a hall-effect sensor installed on the top front of the engine, above the front of the camshaft. The tip of the sensor comes very near a reluctor "pole" piece, cast as part of the camshaft. When this pole piece passes the sensor tip, the disturbance in the sensors magnetic field turns the hall-effect switch "OFF" and "ON" again, producing a signal that the computer can read.
As the camshaft sprocket turns, a magnet in it activates the Hall-effect switch in the cam sensor. When the Hall-effect switch is activated, it grounds the signal line to the Powertrain Control Module (PCM), pulling the cam signal line's applied voltage low. This is interpreted as a cam signal. If the cam signal is not received by the PCM, the PCM will still operate in the SFI mode based on the reference signal, however, SFI mode timing may not be as accurate because the PCM does not know the exact time the intake valve is opening. A loss of this signal or extra cam signals, above 500 RPM, to the PCM will set a Diagnostic Trouble Code (DTC) 17.