STEP IS NOT DONE A DIAGONSTIC TROUBLE
CODE (DTC) MAY BE SET.
VACUUM RESERVOIR
The reservoir contains a one-way check valve to
trap engine vacuum in the reservoir. When engine
vacuum drops, as in climbing a grade while driving,
the reservoir supplies the vacuum needed to main-
tain proper speed control operation. The vacuum res-
ervoir cannot be repaired and must be replaced if
faulty.
VEHICLE SPEED AND DISTANCE
The 4 speed automatic Transmission Control Mod-
ule (TCM) supplies the speed input to the PCM. The
PCM determines acceleration rates. The speed con-
trol software in the PCM uses vehicle speed and
acceleration to control to the set speed.
Vehicles with a 3 speed automatic or manual trans-
mission have a vehicle speed sensor (VSS) mounted
to an adapter near the transmission output shaft.
The sensor is driven through the adapter by a speed-
ometer pinion gear. The VSS pulse signal is moni-
tored by the PCM to determine vehicle speed and to
maintain speed control set speed. Refer to the appro-
priate Powertrain Diagnostic Procedures manual for
diagnosis and testing of this component. Refer to
group 14, Fuel System for Removal/Installation
DIAGNOSIS AND TESTING
ROAD TEST
Perform a vehicle road test to verify reports of
speed control system malfunction. The road test
should include attention to the speedometer. Speed-
ometer operation should be smooth and without flut-
ter at all speeds.
Flutter in the speedometer indicates a problem
which might cause surging in the speed control sys-
tem. The cause of any speedometer problems should
be corrected before proceeding. Refer to Group 8E,
Instrument Panel and Gauges for speedometer diag-
nosis.
If a road test verifies a surge following a set and
the speedometer operates properly see “Overshoot/
Undershoot on speed control set”.
If a road test verifies an inoperative system, and
the speedometer operates properly, check for:
•
A Diagnostic Trouble Code (DTC). If a DTC
exists, conduct tests per the Powertrain Diagnostic
Procedures service manual.
•
A misadjusted brake (stop) lamp switch. This
could also cause an intermittent problem.
•
Loose or corroded electrical connections at the
servo. Corrosion should be removed from electrical
terminals and a light coating of Mopar Multipurpose
Grease, or equivalent, applied.
•
Leaking vacuum reservoir.
•
Loose or leaking vacuum hoses or connections.
•
Defective one-way vacuum check valve.
•
Secure attachment at both ends of the speed
control servo cable.
•
Smooth operation of throttle linkage and throttle
body air valve.
•
Conduct electrical test at PCM.
•
Failed speed control servo. Do the servo vacuum
test.
CAUTION:
When test probing for voltage or conti-
nuity at electrical connectors, care must be taken
not to damage connector, terminals or seals. If
these components are damaged, intermittent or
complete system failure may occur.
OVERSHOOT/UNDERSHOOT FOLLOWING SPEED
CONTROL SET
If the operator repeatedly presses and releases the
set button with their foot off of the accelerator (a “lift
foot set” to begin speed control operation), the vehicle
may accelerate and exceed the desired set speed by
up to 5 MPH (8 km/h) and then decelerate to less
than the desired set speed before finally achieving
the desired set speed.
The Speed Control has an adaptive strategy that
compensates for vehicle-to-vehicle variations in speed
control cable lengths. When the speed control is set
with the vehicle operators foot off of the accelerator
pedal, the speed control thinks there is excessive
speed control cable slack and adapts. If the lift foot
sets are continually used, the speed control over-
shoot/undershoot condition will develop.
To “unlearn” the overshoot/undershoot condition,
the vehicle operator has to press and release the set
button while maintaining the desired set speed with
the accelerator pedal (not decelerating or accelerat-
ing), and then turn the cruise control switch to the
OFF position (or press the CANCEL button if
equipped) after waiting 10 seconds. This procedure
must be performed approximately 10–15 times to
completely unlearn the overshoot/undershoot condi-
tion.
CHECKING FOR DIAGNOSTIC CODES
When trying to verify a speed control system elec-
tronic malfunction: Connect a DRB scan tool if avail-
able to the data link connector. The connector is
located at left side of the steering column, and at
lower edge of the panel.
(1) A speed control malfunction may occur without
a diagnostic code being indicated.
NS
VEHICLE SPEED CONTROL SYSTEM
8H - 3
DESCRIPTION AND OPERATION (Continued)
Summary of Contents for 1998 Voyager
Page 8: ...FASTENER IDENTIFICATION NS INTRODUCTION 5 GENERAL INFORMATION Continued ...
Page 9: ...FASTENER STRENGTH 6 INTRODUCTION NS GENERAL INFORMATION Continued ...
Page 11: ...METRIC CONVERSION 8 INTRODUCTION NS GENERAL INFORMATION Continued ...
Page 12: ...TORQUE SPECIFICATIONS NS INTRODUCTION 9 GENERAL INFORMATION Continued ...
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Page 93: ...RED BRAKE WARNING LAMP FUNCTION NS BRAKES 5 11 DIAGNOSIS AND TESTING Continued ...
Page 94: ...POWER BRAKE SYSTEM DIAGNOSTICS 5 12 BRAKES NS DIAGNOSIS AND TESTING Continued ...
Page 95: ...VEHICLE ROAD TEST BRAKE NOISE NS BRAKES 5 13 DIAGNOSIS AND TESTING Continued ...
Page 222: ...COOLING SYSTEM DIAGNOSIS 7 8 COOLING SYSTEM NS DIAGNOSIS AND TESTING Continued ...
Page 223: ...NS COOLING SYSTEM 7 9 DIAGNOSIS AND TESTING Continued ...
Page 224: ...7 10 COOLING SYSTEM NS DIAGNOSIS AND TESTING Continued ...
Page 225: ...NS COOLING SYSTEM 7 11 DIAGNOSIS AND TESTING Continued ...
Page 226: ...7 12 COOLING SYSTEM NS DIAGNOSIS AND TESTING Continued ...
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Page 289: ...CHARGING SYSTEM SCHEMATIC TYPICAL NS CHARGING SYSTEM 8C 3 DIAGNOSIS AND TESTING Continued ...
Page 291: ...CHARGING SYSTEM TEST NS CHARGING SYSTEM 8C 5 DIAGNOSIS AND TESTING Continued ...
Page 292: ...OVERCHARGE TEST 8C 6 CHARGING SYSTEM NS DIAGNOSIS AND TESTING Continued ...
Page 294: ...VOLTAGE DROP TEST 8C 8 CHARGING SYSTEM NS ...
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Page 377: ...NS GS INSTRUMENT PANEL AND SYSTEMS 8E 5 DIAGNOSIS AND TESTING Continued ...
Page 378: ...8E 6 INSTRUMENT PANEL AND SYSTEMS NS GS DIAGNOSIS AND TESTING Continued ...
Page 379: ...NS GS INSTRUMENT PANEL AND SYSTEMS 8E 7 DIAGNOSIS AND TESTING Continued ...
Page 380: ...8E 8 INSTRUMENT PANEL AND SYSTEMS NS GS DIAGNOSIS AND TESTING Continued ...
Page 381: ...NS GS INSTRUMENT PANEL AND SYSTEMS 8E 9 DIAGNOSIS AND TESTING Continued ...
Page 382: ...8E 10 INSTRUMENT PANEL AND SYSTEMS NS GS DIAGNOSIS AND TESTING Continued ...
Page 383: ...NS GS INSTRUMENT PANEL AND SYSTEMS 8E 11 DIAGNOSIS AND TESTING Continued ...
Page 384: ...8E 12 INSTRUMENT PANEL AND SYSTEMS NS GS DIAGNOSIS AND TESTING Continued ...
Page 385: ...NS GS INSTRUMENT PANEL AND SYSTEMS 8E 13 DIAGNOSIS AND TESTING Continued ...
Page 386: ...8E 14 INSTRUMENT PANEL AND SYSTEMS NS GS DIAGNOSIS AND TESTING Continued ...
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Page 559: ...SPECIAL TOOLS SPECIAL TOOL Degausser 6029 NS OVERHEAD CONSOLE 8V 9 ...
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Page 564: ...8W 01 2 8W 01 GENERAL INFORMATION NS GS DESCRIPTION AND OPERATION Continued ...
Page 565: ...NS GS 8W 01 GENERAL INFORMATION 8W 01 3 DESCRIPTION AND OPERATION Continued ...
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Page 1220: ...Fig 3 Lubrication Lines 9 42 ENGINE NS GS DESCRIPTION AND OPERATION Continued ...
Page 1224: ...ENGINE DIAGNOSIS MECHANICAL CONT 9 46 ENGINE NS GS DIAGNOSIS AND TESTING Continued ...
Page 1286: ...Fig 5 Front Crossmember Dimensions 13 6 FRAME AND BUMPERS NS SPECIFICATIONS Continued ...
Page 1287: ...Fig 6 Engine Compartment Top View NS FRAME AND BUMPERS 13 7 SPECIFICATIONS Continued ...
Page 1289: ...Fig 8 Full Vehicle Bottom View NS FRAME AND BUMPERS 13 9 SPECIFICATIONS Continued ...
Page 1291: ...Fig 11 Body Side Openings NS FRAME AND BUMPERS 13 11 SPECIFICATIONS Continued ...
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Page 1302: ...FUEL PRESSURE BELOW SPECIFICATIONS 14 8 FUEL SYSTEM NS DIAGNOSIS AND TESTING Continued ...
Page 1304: ...FUEL INJECTOR DIAGNOSIS 14 10 FUEL SYSTEM NS DIAGNOSIS AND TESTING Continued ...
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Page 1479: ...Diagnosis Guide NS TRANSAXLE AND POWER TRANSFER UNIT 21 5 DIAGNOSIS AND TESTING Continued ...
Page 1480: ...Diagnosis Guide 21 6 TRANSAXLE AND POWER TRANSFER UNIT NS DIAGNOSIS AND TESTING Continued ...
Page 1481: ...Diagnosis Guide NS TRANSAXLE AND POWER TRANSFER UNIT 21 7 DIAGNOSIS AND TESTING Continued ...
Page 1482: ...Diagnosis Guide 21 8 TRANSAXLE AND POWER TRANSFER UNIT NS DIAGNOSIS AND TESTING Continued ...
Page 1483: ...Diagnosis Guide NS TRANSAXLE AND POWER TRANSFER UNIT 21 9 DIAGNOSIS AND TESTING Continued ...
Page 1484: ...Diagnosis Guide 21 10 TRANSAXLE AND POWER TRANSFER UNIT NS DIAGNOSIS AND TESTING Continued ...
Page 1485: ...Diagnosis Guide NS TRANSAXLE AND POWER TRANSFER UNIT 21 11 DIAGNOSIS AND TESTING Continued ...
Page 1486: ...Diagnosis Guide 21 12 TRANSAXLE AND POWER TRANSFER UNIT NS DIAGNOSIS AND TESTING Continued ...
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Page 1723: ...LEAD CORRECTION CHART NS TIRES AND WHEELS 22 5 DIAGNOSIS AND TESTING Continued ...
Page 1726: ...SPECIFICATIONS TIRE SPECIFICATIONS 22 8 TIRES AND WHEELS NS ...
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