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1 4 - 2 6
FUEL S Y S I E i
S R
D E S C R I P T I O N A N D O P E R A T I O N ( C o n t i n u e d )
power circuit for the Automatic Shutdown (ASD)
relay. The fuse is located i n the PDC. Refer to Group
8W, W i r i n g Diagrams for circuit information.
The P C M controls the fuel pump relay by switch-
ing the ground path for the solenoid side of the relay
on and off. The P C M turns the ground p a t h off w h e n
the ignition switch is i n the Off position. When t h e
ignition switch is i n the O n position, the P C M ener-
gizes the fuel pump. I f the crankshaft position sensor
does not detect engine rotation, the P C M de-ener-
gizes the relay after approximately one second.
The fuel pump relay is located i n the PDC. The
inside top of the PDC cover has a label showing relay
and fuse location.
EVAP PURGE SOLENOID—PCM OUTPUT
The EVAP purge solenoid controls the vacuum
source for the EVAP canister (Fig. 12). The P C M reg-
ulates t h e EVAP purge solenoid.
Fig.
12 Evap
Canister
and LDP
The P C M operates the solenoid by switching t h e
ground circuit on a n d off based on engine operating
conditions. When energized, the solenoid
prevents
vacuum
from
reaching
the evaporative
canister.
When not energized the solenoid allows vacuum to
flow to the canister.
W h e n the P C M grounds the solenoid, i t energizes
and vacuum does n o t operate the evaporative canis-
ter valve. The P C M removes the ground to the sole-
noid
when
the
engine
reaches
a
specified
temperature
and the t i m e
delay
i n t e r v a l has
occurred. When the solenoid de-energizes, vacuum
flows to the canister purge valve. Vapors are purged
from the canister a n d flow to the t h r o t t l e body.
The purge solenoid also energizes d u r i n g certain
idle conditions to update the fuel delivery calibration.
Refer to Group 25 - Evaporative Emissions for
more information.
IDLE AIR CONTROL MOTOR—PCM OUTPUT
The idle a i r control motor is mounted at the front
r i g h t of the intake manifold (Fig. 13). The motor con-
trols a i r flow through a passage connected to both
intake manifold plenums. The P C M operates the idle
air control motor. The P C M adjusts engine idle speed
through the idle a i r control motor to compensate for
engine load or ambient conditions.
Fig.
13 Idle Air Control
Motor
The idle a i r control motor pintle protrudes into a
housing connected to the idle a i r passage. The pintle
controls a i r flow through the intake manifold while
the engine idles. B y extending or retracting the
pintle, the P C M controls adjusts idle speed for differ-
ent operating conditions.
The P C M adjusts the idle a i r control motor based
on inputs i t receives. The inputs affecting idle speed
include throttle position, crankshaft position, engine
coolant temperature, plus brake switch and a i r con-
ditioning request signals. B y increasing airflow when
the t h r o t t l e blade closes quickly at road speeds, the
PCM prevents deceleration die out.
DATA LINK CONNECTOR—PCM OUTPUT
The
data l i n k
connector
(diagnostic
connector)
links the D R B scan tool w i t h the P C M . Refer to On-
Board Diagnostics i n Group 25. (Fig. 14) The data
l i n k connector is located inside the vehicle, below
instrument panel to the left of the clutch pedal.
FUEL INJECTORS—PCM OUTPUT
The fuel injection system uses bottom feed injec-
tors. Fuel enters the bottom of the injector from a
passage i n the intake manifold. The Auto Shutdown
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Troubleshooting
