Electra Park Avenue V6-231 3.8L VIN 3 FI (1988)
Camshaft Position Sensor: Description and Operation
Camshaft Sensor
Camshaft Sensor Magnet
DESCRIPTION
As the camshaft sprocket turns, a magnet mounted on it activates the "hall-effect" switch in the cam sensor. When the "hall-effect" switch is
activated, it grounds the signal line to the C3I module, pulling the cam signal line's applied voltage low. This is interpreted as a cam signal,
"Synchronization-Pulse". Because of the way the signal is created, the signal circuit is always either at a high or low voltage (square wave signal).
While the camshaft sprocket continues to turn, the "hall-effect" switch turns "OFF" as the magnetic field passes the cam sensor resulting in one
signal each time the camshaft makes one revolution.
The cam signal is created as piston # 1 and # 4 reach approximately 25° after top dead center. It is then used by the C3I module to begin the
ignition coil firing sequence starting with the # 3/6 coil. The firing sequence begins with this coil because piston # 6 is now at the correct position
in the compression stroke for the spark plugs to be fired. This cam signal, which actually represents camshaft position due to the sensor's mounting
location, is also used by the Electronic Control Module (ECM) to properly time it's sequential fuel injection operation.
Both the crank sensor and cam sensor signals must be received by the C3I module for the engine to start. When the cam signal is not received from
the C3I module by the ECM terminal "A-11", fuel injection is simultaneous rather than sequential and a Code 41 will be set.
If a Code 41 is present and the engine will start and run, the fault is in circuit 630, the C3I module or the ECM and the C3I module will determine
the ignition timing. If the fault is in the cam sensor circuit, the cam sensor or the cam signal portion of the C3I module, Code 41 may also be
present but the engine will not start, since the C3I module cannot determine the position of the number one piston.
