Chrysler 1998 Voyager Service Manual page 303

NS
GENERAL INFORMATION (Continued)
Fig. 5 Power Distribution Center
CRANKSHAFT POSITION SENSOR
The crankshaft position sensor detects slots cut
into the transmission driveplate extension (Fig. 6).
There are 3 sets of slots. Each set contains 4 slots,
for a total of 12 slots (Fig. 7). Basic timing is set by
the position of the last slot in each group. Once the
Powertrain Control Module (PCM) senses the last
slot, it determines crankshaft position (which piston
will next be at TDC) from the camshaft position sen-
sor input. The 4 pulses generated by the crankshaft
position sensor represent the 69°, 49°, 29°, and 9°
BTDC marks. It may take the PCM one engine rev-
olution to determine crankshaft position.
Fig. 6 Crankshaft Position Sensor
The PCM uses crankshaft position reference to
determine injector sequence, ignition timing and the
presence of misfire. Once the PCM determines crank-
shaft position, it begins energizing the injectors in
sequence.
Fig. 7 Timing Slots
The crankshaft sensor is located on the passengers
side of the transmission housing, above the differen-
tial housing (Fig. 8). The bottom of the sensor is posi-
tioned next to the drive plate.
Fig. 8 Crankshaft Position Sensor Location
CAMSHAFT POSITION SENSOR
The camshaft position sensor provides cylinder
identification to the Powertrain Control Module
(PCM) (Fig. 9). The sensor generates pulses as
groups of notches on the camshaft sprocket pass
underneath it (Fig. 10). The PCM keeps track of
crankshaft rotation and identifies each cylinder by
the pulses generated by the notches on the camshaft
sprocket. Four crankshaft pulses follow each group of
camshaft pulses.
When the PCM receives 2 cam pulses followed by
the long flat spot on the camshaft sprocket, it knows
that the crankshaft timing marks for cylinder 1 are
next (on driveplate). When the PCM receives one
camshaft pulse after the long flat spot on the
sprocket, cylinder number 2 crankshaft timing marks
are next. After 3 camshaft pulses, the PCM knows
IGNITION SYSTEM 8D - 5