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TJ
DESCRIPTION AND OPERATION
POWERTRAIN CONTROL MODULE . . . . . . . . . . 2
SERVO CABLE . . . . . . . . . . . . . . . . . . . . . . . . . . 1
SPEED CONTROL SERVO . . . . . . . . . . . . . . . . . . 1
SPEED CONTROL SOLENOID CIRCUITS . . . . . . 1
SPEED CONTROL SWITCHES . . . . . . . . . . . . . . 1
STOP LAMP SWITCH . . . . . . . . . . . . . . . . . . . . . 1
VACUUM RESERVOIR . . . . . . . . . . . . . . . . . . . . 2
VEHICLE SPEED SENSOR . . . . . . . . . . . . . . . . . 2
DIAGNOSIS AND TESTING
ON-BOARD DIAGNOSTIC TEST FOR SPEED
CONTROL SYSTEM . . . . . . . . . . . . . . . . . . . . . 2
OVERSHOOT/UNDERSHOOT FOLLOWING
SPEED CONTROL SET . . . . . . . . . . . . . . . . . . . 3
DESCRIPTION AND OPERATION
SPEED CONTROL SERVO
The servo unit consists of a solenoid valve body, a
vacuum servo and the mounting bracket. The Power-
train Control Module (PCM) controls the solenoid
valve body. The solenoid valve body controls the
application and release of vacuum to the diaphragm
of the vacuum servo. A cable connects the servo with
the throttle linkage. The servo unit cannot be
repaired and is serviced only as a complete assembly.
SPEED CONTROL SOLENOID CIRCUITS
When all of the speed control parameters are met,
and the SET button is pressed, the PCM actuates the
vent solenoid and "duty-cycles" the vacuum solenoid
to open the throttle and bring the vehicle up to tar-
get speed. When the vehicle is at target speed, it will
actuate the vent solenoid with the vacuum solenoid
de-activated to maintain the vehicle at target speed.
When the vehicle is above target speed, the PCM will
"duty-cycle" the vent solenoid with the vacuum sole-
noid still de-activated to close the throttle to return
to target speed.
SPEED CONTROL SWITCHES
Two separate speed control switch modules are
mounted on the steering wheel to the left and right
side of the driver's airbag module. Within the two
switch modules, five momentary contact switches,
supporting seven different speed control functions
SPEED CONTROL SYSTEM
CONTENTS
page
SPEED CONTROL SYSTEM
ROAD TEST . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
SPEED CONTROL SERVO . . . . . . . . . . . . . . . . . . 3
SPEED CONTROL SWITCHES . . . . . . . . . . . . . . 2
STOP LAMP SWITCH . . . . . . . . . . . . . . . . . . . . . 2
VACUUM SUPPLY TEST . . . . . . . . . . . . . . . . . . . 3
VEHICLE SPEED SIGNAL . . . . . . . . . . . . . . . . . . 2
REMOVAL AND INSTALLATION
SERVO CABLE . . . . . . . . . . . . . . . . . . . . . . . . . . 5
SPEED CONTROL SERVO . . . . . . . . . . . . . . . . . . 4
SPEED CONTROL SWITCH . . . . . . . . . . . . . . . . . 4
STOP LAMP SWITCH . . . . . . . . . . . . . . . . . . . . . 5
VACUUM RESERVOIR . . . . . . . . . . . . . . . . . . . . 6
TORQUE CHART . . . . . . . . . . . . . . . . . . . . . . . . . 6
are used. The outputs from these switches are fil-
tered into one input. The Powertrain Control Module
(PCM) determines which output has been applied
through resistive multiplexing. The input circuit
voltage is measured by the PCM to determine which
switch function has been selected.
A speed control indicator lamp, located on the
instrument panel cluster is energized by the PCM via
the CCD Bus. This occurs when speed control system
power has been turned ON, and the engine is run-
ning.
The two switch modules are labeled: ON/OFF, SET,
RESUME/ACCEL, CANCEL and COAST. Refer to
the owner's manual for more information on speed
control switch functions and setting procedures. The
individual switches cannot be repaired. If one indi-
vidual switch fails, the switch module must be
replaced.
STOP LAMP SWITCH
Vehicles equipped with the speed control option use
a dual function stop lamp switch. The switch is
mounted on the brake pedal mounting bracket under
the instrument panel. The PCM monitors the state of
the dual function stop lamp switch. Refer to the
Brake section for more information on stop lamp
switch service and adjustment procedures.
SERVO CABLE
The speed control servo cable is connected between
the speed control vacuum servo diaphragm and the
throttle body control linkage. This cable causes the
8H - 1
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