Jeep Wrangler 1997 Manual page 798

14 - 26 -
FUEL SYSTEM
DESCRIPTION AND OPERATION (Continued)
PCM will also de-energize the relay if coolant tem-
perature exceeds 125°C (257°F) .
CCD BUS (+/-) CIRCUITS-PCM OUTPUTS
The Powertrain Control Module (PCM) sends cer-
tain output signals through the CCD bus circuits .
These signals are used to control certain instrument
panel located items and to determine certain identi-
fication numbers .
Refer to Group 8E, Instrument Panel and Gauges
for additional information.
GENERATOR FIELD SOURCE (+)-PCM OUTPUT
This output from the Powertrain Control Module
(PCM) regulates charging system voltage to the gen-
erator field source (+) circuit . The voltage range is
12 .9 to 15 .0 volts. Jeep models of previous years had
used the ASD relay to apply the 12 volt + power sup-
ply to the generator field source (+) circuit . Refer to
Groups 8A and 8C for charging system information .
GENERATOR FIELD DRIVER (-)-PCM OUTPUT
This output from the Powertrain Control Module
(PCM) regulates charging system ground control to
the generator field driver (-) circuit . Refer to Groups
8A and 8C for charging system information .
AUTO SHUTDOWN (ASD) RELAY-PCM OUTPUT
The ASD relay is located in the Power Distribution
Center (PDC) (Fig . 2).
The ASD relay supplies battery voltage to the fuel
pump, fuel injector, ignition coil and both oxygen
(02S) sensor heating elements. The ground circuit for
the
coil
in the ASD relay is controlled by the Power-
train Control Module (PCM). The PCM operates the
ASD relay by switching the ground circuit on and off.
FUEL PUMP RELAY-PCM OUTPUT
The PCM energizes the electric fuel pump through
the fuel pump relay. Battery voltage is applied to the
fuel pump relay when the ignition key is ON. The
relay is energized when a ground signal is provided
by the PCM .
The fuel pump will operate for approximately one
second unless the engine is operating or the starter
motor is engaged .
The fuel pump relay is located in the Power Distri-
bution Center (PDC) (Fig. 2).
IDLE AIR CONTROL (IAC) MOTOR-PCM OUTPUT
The IAC motor is mounted on the throttle body
(Fig. 7) and is controlled by the Powertrain Control
Module (PCM) .
The throttle body has an air control passage that
provides air for the engine at idle (the throttle plate
is closed) . The IAC motor pintle protrudes into the
air control passage and regulates air flow through it.
Based on various sensor inputs, the PCM adjusts
engine idle speed by moving the IAC motor pintle in
and out of the air control passage . The IAC motor is
positioned when the ignition key is turned to the On
position.
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate. Never attempt to adjust the engine idle
speed using this screw. All idle speed functions are
controlled by the PCM .
DUTY CYCLE EVAP PURGE SOLENOID VALVE-PCM
OUTPUT
Refer to Group 25, Emission Control System for
information .
DATA LINK CONNECTOR-PCM INPUT AND
OUTPUT
The 16-way data link connector (diagnostic scan
tool connector) links the Diagnostic Readout Box
(DRB) scan tool or the Mopar Diagnostic System
(MDS) with the powertrain control module (PCM).
The data link connector is located under the instru-
ment panel to the left of the steering column (Fig.
10) . For operation of the DRB scan tool, refer to the
appropriate Powertrain Diagnostic Procedures ser-
vice manual .
WWIWIN
80a4835f
Fig. 10 Data Link Connector Location
TJ
16-WAY
DATA LINK
CONNECTOR
12
FUEL INJECTORS-PCM OUTPUT
Six individual fuel injectors are used with the 4.OL
6-cylinder engine . Four individual fuel injectors are
used with the 2.5L 4-cylinder engine . The injectors
are attached to the fuel rail (Fig. 11) .
The nozzle ends of the injectors are positioned into
openings in the intake manifold just above the intake