Jeep 1996 Grand Cherokee Service Manual page 275

8D - 4 IGNITION SYSTEM
DESCRIPTION AND OPERATION (Continued)
Fig. 4 Crankshaft Position Sensor Location—4.0L
6-Cyl. Engine
other inputs, to determine injector sequence and igni-
tion timing.
The sensor is a hall effect device combined with an
internal magnet. It is also sensitive to steel within a
certain distance from it.
SENSOR OPERATION
The flywheel/drive plate has groups of four notches
at its outer edge. On 4.0L 6-cylinder engines there
are three sets of notches (Fig. 5).
The notches cause a pulse to be generated when
they pass under the sensor. The pulses are the input
to the PCM. For each engine revolution there are 3
groups of four pulses generated on 4.0L 6-cylinder
engines.
The trailing edge of the fourth notch, which causes
the pulse, is four degrees before top dead center
(TDC) of the corresponding piston.
The engine will not operate if the PCM does not
receive a crankshaft position sensor input.
CAMSHAFT POSITION SENSOR
The camshaft position sensor is located in the dis-
tributor on all engines.
The sensor contains a hall effect device called a
sync signal generator to generate a fuel sync signal.
This sync signal generator detects a rotating pulse
ring (shutter) on the distributor shaft. The pulse ring
rotates 180 degrees through the sync signal genera-
tor. Its signal is used in conjunction with the crank-
shaft position sensor to differentiate between fuel
Fig. 5 Sensor Operation—4.0L 6-Cyl. Engine
injection and spark events. It is also used to synchro-
nize the fuel injectors with their respective cylinders.
When the leading edge of the pulse ring (shutter)
enters the sync signal generator, the following occurs:
The interruption of magnetic field causes the voltage
to switch high resulting in a sync signal of approxi-
mately 5 volts.
When the trailing edge of the pulse ring (shutter)
leaves the sync signal generator, the following occurs:
The change of the magnetic field causes the sync sig-
nal voltage to switch low to 0 volts.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
For an operational description, diagnosis and
removal/installation procedures, refer to Group 14,
Fuel System.
ENGINE COOLANT TEMPERATURE SENSOR
For an operational description, diagnosis and
removal/installation procedures, refer to Group 14,
Fuel System.
THROTTLE POSITION SENSOR
For an operational description, diagnosis and
removal/installation procedures, refer to Group 14,
Fuel System.
INTAKE MANIFOLD AIR TEMPERATURE SENSOR
For an operational description, diagnosis and
removal/installation procedures, refer to Group 14,
Fuel System.
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