automatic transmission CHRYSLER VOYAGER 1996 User Guide

²Transmission range sensor, or Park/Neutral
Position switch with automatic transmissions
²Clutch Pedal Position Switch with manual
transmissions
²Ignition switch
²Battery
²All related wiring and connections
CAUTION: Before performing any starter tests, the
ignition and fuel systems must be disabled.
²To disable ignition and fuel systems, disconnect
the Automatic Shutdown Relay (ASD). The ASD relay
is located in the in the Power Distribution Center
(PDC). Refer to the PDC cover for the proper relay
location.
STARTER SOLENOID
WARNING: CHECK TO ENSURE THAT THE TRANS-
MISSION IS IN THE PARK POSITION WITH THE
PARKING BRAKE APPLIED
(1) Verify battery condition. Battery must be in
good condition with a full charge before performing
any starter tests. Refer to Battery Tests.
(2) Perform Starter Solenoid test BEFORE per-
forming the starter relay test.
(3) Raise the vehicle.
(4) Perform a visual inspection of the starter/
starter solenoid for corrosion, loose connections or
faulty wiring.
(5) Lower the vehicle.
(6) Locate and remove the starter relay from the
Power Distribution Center (PDC). Refer to the PDC
label for relay identification and location.
(7) Connect a remote starter switch or a jumper
wire between the remote battery positive post and
terminal 87 of the starter relay connector.
(a) If engine cranks, starter/starter solenoid is
good. Go to the Starter Relay Test.
(b) If engine does not or solenoid chatters, check
wiring and connectors from starter relay to starter
solenoid for loose or corroded connections. Particu-
larly at starter terminals.
(c) Repeat test. If engine still fails to crank prop-
erly, trouble is within starter or starter mounted
solenoid, and replace starter.
STARTER RELAY
WARNING: CHECK TO ENSURE THAT THE TRANS-
MISSION IS IN THE PARK POSITION/NEUTRAL
WITH THE PARKING BRAKE APPLIED
RELAY TEST
The starter relay is located in the Power Distribu-
tion Center (PDC) in the engine compartment. Refer
to the PDC label for relay identification and location.
Remove the starter relay from the PDC as
described in this group to perform the following tests:
(1) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to Step 2. If not OK, replace the faulty relay.
(2) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 7565 ohms. If OK, go to Step
3. If not OK, replace the faulty relay.
(3) Connect a battery B+ lead to terminals 86 and
a ground lead to terminal 85 to energize the relay.
The relay should click. Also test for continuity
between terminals 30 and 87, and no continuity
between terminals 87A and 30. If OK, refer to Relay
Circuit Test procedure. If not OK, replace the faulty
relay.
RELAY CIRCUIT TEST
(1) The relay common feed terminal cavity (30) is
connected to battery voltage and should be hot at all
times. If OK, go to Step 2. If not OK, repair the open
circuit to the PDC fuse as required.
(2) The relay normally closed terminal (87A) is
connected to terminal 30 in the de-energized position,
but is not used for this application. Go to Step 3.
(3) The relay normally open terminal (87) is con-
nected to the common feed terminal (30) in the ener-
gized position. This terminal supplies battery voltage
to the starter solenoid field coils. There should be
continuity between the cavity for relay terminal 87
and the starter solenoid terminal at all times. If OK,
go to Step 4. If not OK, repair the open circuit to the
starter solenoid as required.
(4) The coil battery terminal (86) is connected to
the electromagnet in the relay. It is energized when
the ignition switch is held in the Start position. On
Starter Relay
8B - 2 STARTERNS
DIAGNOSIS AND TESTING (Continued)

vehicles with a manual transmission, the clutch
pedal must be fully depressed for this test. Check for
battery voltage at the cavity for relay terminal 86
with the ignition switch in the Start position, and no
voltage when the ignition switch is released to the
On position. If OK, go to Step 5. If not OK with an
automatic transmission, check for an open or short
circuit to the ignition switch and repair, if required.
If the circuit to the ignition switch is OK, see the
Ignition Switch Test procedure in this group. If not
OK with a manual transmission, check the circuit
between the relay and the clutch pedal position
switch for an open or a short. If the circuit is OK, see
the Clutch Pedal Position Switch Test procedure in
this group.
(5) The coil ground terminal (85) is connected to
the electromagnet in the relay. On vehicles with an
automatic transmission, it is grounded through the
park/neutral position switch only when the gearshift
selector lever is in the Park or Neutral positions. On
vehicles with a manual transmission, it is grounded
at all times. Check for continuity to ground at the
cavity for relay terminal 85. If not OK with an auto-
matic transmission, check for an open or short circuit
to the park/neutral position switch and repair, if
required. If the circuit is OK, see the Park/Neutral
Position Switch Test procedure in this group. If not
OK with a manual transmission, repair the circuit to
ground as required.
SAFETY SWITCHES
For diagnostics,
²Clutch Pedal Position Switch, refer to Group 6,
Clutch.
²Park/Neutral Position Switch, refer to Group 21,
Transaxle
IGNITION SWITCH
After testing starter solenoid and relay, test igni-
tion switch and wiring. Refer to Group 8D, Ignition
Systems or Group 8W, Wiring Diagrams. Check all
wiring for opens or shorts, and all connectors for
being loose or corroded.
BATTERY
Refer to Group 8A, Battery for proper procedures.
ALL RELATED WIRING AND CONNECTORS
Refer to Group 8W, Wiring Diagrams,
FEED CIRCUIT RESISTANCE TEST
Before proceeding with this operation, review Diag-
nostic Preparation and Starter Feed Circuit Tests.
The following operation will require a voltmeter,
accurate to 1/10 of a volt.
CAUTION: Before performing any starter tests, the
ignition and fuel systems must be disabled.
(1) To disable the ignition and fuel systems, dis-
connect the Automatic Shutdown Relay (ASD). The
ASD relay is located in the Power Distribution Cen-
ter (PDC). Refer to the PDC cover for proper relay
location.
(2) With all wiring harnesses and components
properly connected, perform the following:
(a) Connect the negative lead of the voltmeter to
the battery negative post, and positive lead to the
battery negative cable clamp (Fig. 2). Rotate and
hold the ignition switch in the START position.
Observe the voltmeter. If voltage is detected, cor-
rect poor contact between cable clamp and post.
(b) Connect positive lead of the voltmeter to the
battery positive post, and negative lead to the bat-
tery positive cable clamp. Rotate and hold the igni-
tion switch key in the START position. Observe the
voltmeter. If voltage is detected, correct poor con-
tact between the cable clamp and post.
(c) Connect negative lead of voltmeter to battery
negative terminal, and positive lead to engine
Fig. 2 Test Battery Connection Resistance
NSSTARTER 8B - 3
DIAGNOSIS AND TESTING (Continued)

CAUTION: Before performing any starter tests, the
ignition and fuel systems must be disabled.
(1) Connect a volt-ampere tester to the battery ter-
minals (Fig. 7). Refer to the operating instructions
provided with the tester being used.
(2) To disable the ignition and fuel systems, dis-
connect the Automatic Shutdown Relay (ASD). The
ASD relay is located in the Power Distribution Cen-
ter (PDC). Refer to the PDC cover for proper relay
location. The 2.5L Diesel Engine, to disable the
engine from starting, disconnect wire connector from
the Fuel Solenoid.
(3) Verify that all lights and accessories are OFF,
and the transmission shift selector is in the PARK
position or with the clutch pedal depressed and SET
parking brake.
CAUTION: Do not overheat the starter motor or
draw the battery voltage below 9.6 volts during
cranking operations.
(4) Rotate and hold the ignition switch in the
START position. Observe the volt-ampere tester (Fig.
6).
²If voltage reads above 9.6 volts, and amperage
draw reads above 280 amps or the Diesel engine
above 450 amps, check for engine seizing or faulty
starter.
²If voltage reads 12.4 volts or greater and amper-
age reads 0 to 10 amps, check for corroded cables
and/or bad connections.
²Voltage below 9.6 volts and amperage draw
above 300 amps or Diesel engine above 500 amps,
the problem is the starter. Replace the starter refer
to starter removal.
(5) After the starting system problems have been
corrected, verify the battery state-of-charge and
charge battery if necessary. Disconnect all testingequipment and connect ASD relay or the Fuel Sole-
noid. Start the vehicle several times to assure the
problem has been corrected.
REMOVAL AND INSTALLATION
STARTERÐ2.4L ENGINE
REMOVAL
(1) Release hood latch and open hood.
(2) Disconnect battery negative cable (Fig. 8).
(3) Hoist and support vehicle on safety stands.
(4) Disconnect solenoid wire connector from termi-
nal.
(5) Remove nut holding B+ wire to terminal.
(6) Disconnect solenoid and B+ wires from starter
terminals.
(7) Remove bolts holding starter to transaxle bell-
housing (Fig. 9).
(8) Remove starter.
Fig. 7 Volt-Ampere Tester Connections
Fig. 8 Battery Negative Cable
Fig. 9 Starter±2.4L Engine
NSSTARTER 8B - 5
DIAGNOSIS AND TESTING (Continued)

IGNITION SWITCH AND LOCK CYLINDER
INDEX
page page
DESCRIPTION AND OPERATION
IGNITION INTERLOCK.................... 35
LOCK KEY CYLINDER.................... 35
REMOVAL AND INSTALLATION
IGNITION INTERLOCK.................... 38IGNITION SWITCH....................... 35
LOCK CYLINDER HOUSING............... 38
LOCK KEY CYLINDER.................... 38
DESCRIPTION AND OPERATION
IGNITION INTERLOCK
All vehicles equipped with automatic transaxles
have an interlock system. The system prevents shift-
ing the vehicle out of Park unless the ignition lock
cylinder is in the Off, Run or Start position. In addi-
tion, the operator cannot rotate the key to the lock
position unless the shifter is in the park position. On
vehicles equipped with floor shift refer to Group 21 -
Transaxle for Automatic Transmission Shifter/Igni-
tion Interlock.
LOCK KEY CYLINDER
The lock cylinder is inserted in the end of the
housing opposite the ignition switch. The ignition key
rotates the cylinder to 5 different detents (Fig. 1):
²Accessory
²Off (lock)
²Unlock
²On/Run
²Start
REMOVAL AND INSTALLATION
IGNITION SWITCH
The ignition switch attaches to the lock cylinder
housing on the end opposite the lock cylinder (Fig. 2).
For ignition switch terminal and circuit identifica-
tion, refer to Group 8W, Wiring Diagrams.
Fig. 1 Ignition Lock Cylinder Detents
Fig. 2 Ignition SwitchÐViewed From Below Column
NSIGNITION SYSTEM 8D - 35

The instrument cluster is equipped with the follow-
ing warning lamps.
²Lift Gate Ajar
²Low Fuel Level
²Low Windshield Washer Fluid Level
²Cruise
²Battery Voltage
²Fasten Seat Belt
²Door Ajar
DIAGNOSIS AND TESTING
DIAGNOSTIC PROCEDURES
NS vehicle instrument clusters are equipped with a
self diagnostic test feature to help identify electronic
problems. Prior to any test, perform Self Diagnostic
Test. The self diagnostic system monitors the CCD
bus messages. If an electronic problem occurs, a
Diagnostic Trouble Code (DTC) will be displayed in
the odometer window of the cluster.
The following CCD bus messages are continuously
monitored by the diagnostic system:
²Body Control Module
²Powertrain Control Module
²Transmission Control Module, if equipped
HEADLAMP SWITCH
Using a Digital Multimeter, equipped with a diode
test to perform the Headlamp Switch Test below (Fig.
1).
Switch position possibilities are open (no continu-
ity), continuity, resistance value in ohms, or diode
test. Use the values in the third column to determine
meter setting. If Headlamp Switch is not within spec-
ifications replace as necessary.
The Chrysler Town and Country is available with
optional Automatic Headlamps. For diagnosis, refer
to the proper Body Diagnostic Procedures Manual.
SELF DIAGNOSTIC TEST
To activate self diagnostic program:
(1) With the ignition switch in the OFF position,
depress the TRIP and RESET buttons.
(2) While holding the TRIP and RESET button
turn the ignition switch to the ON position.
(3) Continue to hold the TRIP and RESET buttons
until the word CODE appears in the odometer win-
dows (about five seconds) then release the buttons. If
a problem exists, the system will display Diagnostic
Trouble Codes (DTC's). If no problem exists, the code
999 (End Test) will momentarily appear.
DIM TEST
When CHEC-0 is displayed in the odometer win-
dow, the cluster's vacuum fluorescent (VF) displayswill dim down. If the VF display brightness does no
change, a problem exists in the cluster.
Fig. 1 Headlamp Switch Test
8E - 2 INSTRUMENT PANEL AND SYSTEMSNS
DESCRIPTION AND OPERATION (Continued)

SPEEDOMETER DIAGNOSIS
CONDITION POSSIBLE CAUSES CORRECTION
NO POINTER
MOVEMENT1. Internal cluster failure. 1. (a) Perform cluster self diagnostic test and check for
fault codes.
²If speedometer pointer moves to calibration points
during test and fault codes 110 or 111 don't appear in
the odometer display then failure is not in the cluster.
Look for another possible cause of failure.
²If the pointer doesn't move during test, go to Step
(b).
²If fault code 110 is displayed in the odometer, go to
Step (b).
²If fault code 111 is displayed in the odometer then go
to Step (f).
²If fault codes 905, 920, or 940 are displayed in the
odometer display refer to the fault code chart to identify
which module is causing the fault and repair module.
(b) Replace main cluster pc board. Go to Step (c).
(c) Connect cluster into instrument panel wiring
harness. Place it back into the proper position in the
instrument panel. Put in the top two mounting screws to
hold the cluster in place. DO NOT COMPLETELY
INSTALL CLUSTER TO INSTRUMENT PANEL UNTIL
UNIT IS CALIBRATED AND TESTED. Go to Step (d).
(d) Use a scan tool to calibrate cluster and perform Self
Diagnostic Test. If OK, complete installation. If not OK,
go to Step (e).
(e) Replace subdial assembly and use a scan tool to
calibrate cluster. If not OK, look at another possible
cause for the speedometer failure.
(f) Use a scan tool to calibrate speedometer and
perform Self Diagnostic Test. If OK, stop. If not OK, go
to Step (b).
2. No speed CCD Bus
Message or Zero mph
CCD Speed Bus
Message.2. (a) Check the Body Control Module (BCM) using a
scan tool. If OK, go to Step (b). If not OK, refer to the
BCM section of the service manual to repair the BCM.
(b) Check the Powertrain Control Module (PCM) using
a scan tool. If OK, go to Step (c). If not OK, refer to the
PCM section of the service manual to repair the PCM.
(c) Check the speed signal input into the PCM. The
speed signal originates from one of the following
sources:
²A distance sensor for vehicles with 3 speed automatic
transmission. Check continuity from distance sensor to
PCM. If OK, replace distance sensor. If not OK, repair
wiring.
²The Electronic Transmission Control Module (TCM)
for vehicles with the 4 speed electronic transmissions.
Check continuity from TCM to PCM. If OK, use a scan
tool to check TCM. Refer to the electronic TCM section
of the service manual to repair the TCM. If not OK,
repair wiring.
8E - 4 INSTRUMENT PANEL AND SYSTEMSNS
DIAGNOSIS AND TESTING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
ERRATIC POINTER
MOVEMENT1. Erratic Message from
another Module.1. (a) Check the BCM using a scan tool If OK, go to
Step (b). If not OK, refer to the BCM section of the
service manual to repair the BCM.
(b) Check the PCM using a scan tool. If OK, go to Step
(c). If not OK, refer to the PCM section of the service
manual to repair the PCM.
(c) Check the speed signal input into the PCM. The
speed signal originates from one of the following
sources:
²A distance sensor for vehicles with 3 speed automatic
transmission. Check continuity from distance sensor to
PCM. If OK, replace distance sensor. If not OK, repair
wiring.
²The Electronic Transmission Control Module (TCM)
vehicles with the 4 speed electronic transmissions.
Check continuity from TCM to engine controller. If OK,
use a scan tool to check TCM. Refer to the electronic
section of the service manual to repair the TCM. If not
OK, repair wiring.
2. Internal Cluster Failure. 2. (a) Perform cluster self diagnostic test and check for
fault codes.
²If the pointer moves during test but still appears
erratic and fault codes 110 or 111 don't appear in the
odometer display, then go to Step (b).
²If fault code 110 is displayed in the odometer, go to
Step (e).
²If fault code 111 appears in the odometer display go
to Step (d).
²If fault codes 905, 920, or 940 are displayed in the
odometer display refer to the fault code chart to identify
which module is causing the fault and repair module.
(b) Replace cluster subdial assembly. To Step (c).
(c) Connect cluster into instrument panel wiring
harness. Place it back into the proper position in the
instrument panel. Put in the top two mounting screws to
hold the cluster in place. DO NOT COMPLETELY
INSTALL CLUSTER TO INSTRUMENT PANEL UNTIL
UNIT IS CALIBRATED AND TESTED. Go to Step (d).
(d) Use a scan tool to calibrate cluster and perform Self
Diagnostic Test. If OK, continue installation. If not OK,
go to Step (e).
Replace main cluster pc board and use a scan tool to
calibrate cluster. If not OK, look at another possible
cause for the speedometer failure.
NSINSTRUMENT PANEL AND SYSTEMS 8E - 5
DIAGNOSIS AND TESTING (Continued)

VEHICLE SPEED CONTROL SYSTEM
CONTENTS
page page
GENERAL INFORMATION
INTRODUCTION......................... 1
DESCRIPTION AND OPERATION
AUTOMATIC SPEED CONTROL OVERSPEED
REDUCTION........................... 2
POWERTRAIN CONTROL MODULE.......... 2
SERVO CABLE.......................... 2
SPEED CONTROL SERVO.................. 1
SPEED CONTROL SWITCHES.............. 1
STOP LAMP SWITCH..................... 2
VACUUM RESERVOIR.................... 3
VEHICLE SPEED AND DISTANCE............ 3
DIAGNOSIS AND TESTING
CHECKING FOR DIAGNOSTIC CODES........ 3
ELECTRICAL TESTS AT POWERTRAIN
CONTROL MODULE..................... 6OVERSHOOT/UNDERSHOOT FOLLOWING
SPEED CONTROL SET................... 3
ROAD TEST............................ 3
SERVO VACUUM TEST.................... 6
SPEED CONTROL ELECTRICAL TEST........ 4
SPEED CONTROL SWITCH TEST............ 6
STOP LAMP SWITCH TEST................ 6
VACUUM SUPPLY TEST................... 8
VEHICLE SPEED SENSOR................. 8
REMOVAL AND INSTALLATION
POWERTRAIN CONTROL MODULE.......... 9
SPEED CONTROL CABLE.................. 9
SPEED CONTROL SERVO.................. 8
SPEED CONTROL SWITCHES.............. 9
STOP LAMP SWITCH.................... 9
VACUUM RESEROIR..................... 10
VEHICLE SPEED SENSOR................ 10
GENERAL INFORMATION
INTRODUCTION
The speed control system is electronically con-
trolled and vacuum operated. The electronic control
is integrated into the powertrain control module,
located next to battery. The controls are located on
the steering wheel and consist of the ON/OFF, SET,
RESUME/ACCEL, CANCEL and DECEL buttons
(Fig. 1).
DESCRIPTION AND OPERATION
SPEED CONTROL SERVO
The servo unit consists of a solenoid valve body,
and a vacuum chamber. The PCM controls the sole-
noid valve body. The solenoid valve body controls the
application and release of vacuum to the diaphragm
of the vacuum servo. The servo unit cannot be
repaired and is serviced only as a complete assembly.
SPEED CONTROL SWITCHES
There are two separate switch pods that operate
the speed control system. The steering-wheel-
mounted switches use multiplexed circuits to provide
inputs to the PCM for ON, OFF, RESUME, ACCEL-
ERATE, SET, DECEL and CANCEL modes. Refer to
the owner's manual for more information on speed
control switch functions and setting procedures.
When speed control is selected by depressing the
ON switch, the PCM allows a set speed to be stored
in RAM for speed control. To store a set speed,
depress the SET switch while the vehicle is moving
at a speed between 30 and 85 mph. In order for the
speed control to engage, the brakes cannot be
applied, nor can the gear selector be indicating the
transmission is in Park or Neutral.
The speed control can be disengaged manually by:
²Stepping on the brake pedal
Fig. 1 Speed Control Switches
NSVEHICLE SPEED CONTROL SYSTEM 8H - 1

²Depressing the OFF switch
²Depressing the CANCEL switch.
NOTE: Depressing the OFF switch or turning off
the ignition switch will erase the set speed stored
in the PCM.
For added safety,the speed control system is pro-
grammed to disengaged for any of the following con-
ditions:
²An indication of Park or Neutral
²An rpm increase without a VSS signal increase
(indicates that the clutch has been disengaged)
²Excessive engine rpm (indicates that the trans-
mission may be in a low gear)
²The VSS signal increases at a rate of 10 mph
per second (indicates that the co-efficient of friction
between the road surface and tires is extremely low)
²The VSS signal decreases at a rate of 10 mph
per second (indicates that the vehicle may have
decelerated at an extremely high rate)
²If the actual speed is not within 20 mph of the
set speed
The previous disengagement conditions are pro-
grammed for added safety.
Once the speed control has been disengaged,
depressing the ACCEL switch when speed is greater
than 25 mph restores the vehicle to the target speed
that was stored in the PCM.
NOTE: Depressing the OFF switch will erase the
set speed stored in the PCM's RAM.
While the speed control is engaged, the driver can
increase the vehicle speed by depressing the ACCEL
switch. The new target speed is stored in the PCM
when the ACCEL is released. The PCM also has a
9tap-up9feature in which vehicle speed increases at a
rate of approximately 2 mph for each momentary
switch activation of the ACCEL switch. The PCM
also provides a means to decelerate without disen-
gaging speed control. To decelerate from an existing
recorded target speed, depress and hold the COAST
switch until the desired speed is reached, then
release the switch.
The individual switches cannot be repaired. If one
switch fails, the entire switch module must be
replaced.
AUTOMATIC SPEED CONTROL OVERSPEED
REDUCTION
Transmission control software includes an auto-
matic speed control overspeed reduction feature. This
maintains vehicle speed at the selected set point
when descending a grade.
The Transmission Control Module (TCM) first
senses that the speed control is set. If the set speedis exceeded by more than 4 mph (6.5 km/hr) and the
throttle is closed, the TCM causes the transaxle to
downshift to THIRD gear. After downshifting, the
automatic speed control resumes normal operation.
To ensure that an upshift is appropriate after the set
speed is reached, the TCM waits until the speed con-
trol system opens the throttle at least 8 degrees
before upshifting to OVERDRIVE again.
If the driver applies the brakes, canceling auto-
matic speed control operation with the transaxle still
in THIRD gear, the TCM maintains this gear until
the driver opens the throttle at least 8 degrees to
avoid an inappropriate upshift. The upshift is also
delayed for 0.5 seconds after reaching the 8 degrees
throttle opening in anticipation that the driver might
open the throttle enough to require THIRD gear.
This will avoid unnecessary and disturbing transmis-
sion cycling. If the automatic speed control RESUME
feature is used after braking, the upshift is delayed
until the set speed is achieved to reduce cycling and
provide better response.
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 Group 5,
Brakes for more information on stop lamp switch ser-
vice 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
throttle control linkage to open or close the throttle
valve in response to movement of the vacuum servo
diaphragm.
POWERTRAIN CONTROL MODULE
The speed control electronic control circuitry is
integrated into the Powertrain Control Module
(PCM). The PCM is located in the engine compart-
ment. The PCM speed control functions are moni-
tored by the On-Board Diagnostics (OBD). All OBD-
sensed systems are monitored by the PCM. Each
monitored circuit is assigned a Diagnostic Trouble
Code (DTC). The PCM will store a DTC in electronic
memory for any failure it detects. See On-Board
Diagnostic Tests in this group for more information.
The PCM cannot be repaired and must be replaced if
faulty.
USE THE DRB SCAN TOOL TO REPROGRAM
THE NEW PCM WITH THE VEHICLES ORIGI-
NAL IDENTIFICATION NUMBER (VIN) AND
THE ORGINAL VEHICLES MILAGE. IF THIS
8H - 2 VEHICLE SPEED CONTROL SYSTEMNS
DESCRIPTION AND OPERATION (Continued)

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 ªOvershoot/
Undershoot on speed control setº.
If a road test verifies an inoperative system, and
the speedometer operates properly, check for:
²A Diagnostic Trouble Code (DTC). If a DTC
exists, conduct tests per the Powertrain Diagnostic
Procedures service manual.
²A misadjusted brake (stop) lamp switch. This
could also cause an intermittent problem.
²Loose or corroded electrical connections at the
servo. Corrosion should be removed from electricalterminals and a light coating of Mopar Multipurpose
Grease, or equivalent, applied.
²Leaking vacuum reservoir.
²Loose or leaking vacuum hoses or connections.
²Defective one-way vacuum check valve.
²Secure attachment at both ends of the speed
control servo cable.
²Smooth operation of throttle linkage and throttle
body air valve.
²Conduct electrical test at PCM.
²Failed 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 ªlift
foot setº 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 ªunlearnº 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.
NSVEHICLE SPEED CONTROL SYSTEM 8H - 3
DESCRIPTION AND OPERATION (Continued)