AUTOMATIC SHUTDOWN RELAY
DESCRIPTION
The ASD relay is located in the PDC (Fig. 6). The
inside top of the PDC cover has a label showing relay
and fuse identification.
OPERATION
The Automatic Shutdown (ASD) relay supplies bat-
tery voltage to the fuel injectors, generator field, elec-
tronic ignition coil and the heating elements in the
oxygen sensors.
Refer to the Wiring Diagrams for circuit informa-
tion.
The PCM controls the ASD relay by switching the
ground path for the solenoid side of the relay on and
off. The PCM turns the ground path off when the
ignition switch is in the Off position unless the O2
Heater Monitor test is being run. Refer to the
On-Board Diagnostics in the Emission Control sec-
tion. When the ignition switch is in On or Start, the
PCM momentarily turns on the ASD relay. While the
relay is on the PCM monitors the crankshaft and
camshaft position sensor signals to determine engine
speed and ignition timing (coil dwell). If the PCM
does not receive crankshaft and camshaft position
sensor signals when the ignition switch is in the Run
position, it will de-energize the ASD relay.
CRANKSHAFT POSITION SENSOR—2.0/2.4L
DESCRIPTION
The crankshaft position sensor mounts to the
engine block behind the generator, just above the oil
filter (Fig. 7).
OPERATION
The PCM determines what cylinder to fire from the
crankshaft position sensor input and the camshaft
position sensor input. The second crankshaft counter-
weight has machined into it two sets of four timing
reference notches including a 60 degree signature
notch (Fig. 8). From the crankshaft position sensor
input the PCM determines engine speed and crank-
shaft angle (position).
Fig. 5 Ignition Coil—2.5L Engine
Fig. 6 Power Distribution Center (PDC)
Fig. 7 Crankshaft Position Sensor
8D - 4 IGNITION SYSTEM JA
DESCRIPTION AND OPERATION (Continued)
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