1996 CHRYSLER VOYAGER turn signal

normal. This may indicate:(1)Abnormal loss of
brake fluid in the master cylinder fluid reservoir
resulting from a leak in the hydraulic system.(2)
Brake shoe linings which have worn to a point
requiring replacement.
As the brake fluid drops below the minimum level,
the brake fluid level sensor closes to ground the
brake warning light circuit. This will turn on the red
brake warning light. At this time, master cylinder
fluid reservoir should be checked and filled to the full
mark with DOT 3 brake fluid.If brake fluid level
has dropped below the add line in the master
cylinder fluid reservoir, the entire brake
hydraulic system should be checked for evi-
dence of a leak.
STOP LAMP SWITCH
The stop lamp switch controls operation of the
vehicles stop lamps. Also, if the vehicle is equippedwith speed control, the stop lamp switch will deacti-
vate speed control when the brake pedal is
depressed.
The stop lamp switch controls operation of the
right and left tail, stop and turn signal lamp and
CHMSL lamp, by supplying battery current to these
lamps.
The stop lamp switch controls the lamp operation
by opening and closing the electrical circuit to the
stop lamps.
HUB/BEARING REAR WHEEL
The rear hub and bearing assembly used on this
vehicle is serviceable only as a complete assembly. No
attempt should be made to disassemble a rear hub
and bearing assembly in an effort to repair it.
The rear hub and bearing assembly is attached to
the rear axle using 4 mounting bolts that are remov-
able from the back of the rear hub/bearing.
DIAGNOSIS AND TESTING
BRAKE SYSTEM BASIC DIAGNOSIS GUIDE
SYMPTOMCHART 1
MISC.
COND.CHART 2
WARNING
LIGHTCHART 3
POWER
BRAKESCHART 4
BRAKE
NOISECHART 5
WHEEL
BRAKES
Brake Warning Light On X NO NO
Excessive Pedal Travel 6 X NO O
Pedal Goes To The Floor 6 X
Stop Light On Without Brakes 3
All Brakes Drag 5
Rear Brakes Drag 2 NO NO
Grabby Brakes O X
Spongy Brake Pedal X NO
Premature Rear Brake Lockup 4 NO NO O
Excessive Pedal Effort 1 O
Rough Engine Idle NO O
Brake Chatter (Rough) NO NO X
Surge During Braking NO NO X
Noise During Braking NO NO X
Rattle Or Clunking Noise NO NO X
Pedal Pulsates During Braking NO NO X
Pull To Right Or Left NO NO X
No: Not A Possible Cause X: Most Likely Cause O: Possible Cause
NSBRAKES 5 - 9
DESCRIPTION AND OPERATION (Continued)

ABS BRAKES OPERATION AND VEHICLE
PERFORMANCE
This ABS System represents the current state-of-
the-art in vehicle braking systems and offers the
driver increased safety and control during braking.
This is accomplished by a sophisticated system of
electrical and hydraulic components. As a result,
there are a few performance characteristics that may
at first seem different but should be considered nor-
mal. These characteristics are discussed below.
NORMAL BRAKING SYSTEM FUNCTION
Under normal braking conditions, the ABS System
functions the same as a standard brake system with
a diagonally split master cylinder and conventional
vacuum assist.
ABS SYSTEM OPERATION
If a wheel locking tendency is detected during a
brake application, the brake system will enter the
ABS mode. During ABS braking, hydraulic pressure
in the four wheel circuits is modulated to prevent
any wheel from locking. Each wheel circuit is
designed with a set of electric solenoids to allow mod-
ulation, although for vehicle stability, both rear
wheel solenoids receive the same electrical signal.
During an ABS stop, the brakes hydraulic system
is still diagonally split. However, the brake system
pressure is further split into four control channels.
During antilock operation of the vehicle's brake sys-
tem the front wheels are controlled independently
and are on two separate control channels and the
rear wheels of the vehicle are controlled together.
The system can build and release pressure at each
wheel, depending on signals generated by the wheel
speed sensors (WSS) at each wheel and received at
the Controller Antilock Brake (CAB).
ABS operation is available at all vehicle speeds
above 3 to 5 mph. Wheel lockup may be perceived at
the very end of an ABS stop and is considered nor-
mal.
VEHICLE HANDLING PERFORMANCE DURING
ABS BRAKING
It is important to remember that an antilock brake
system does not shorten a vehicle's stopping distance
under all driving conditions, but does provide
improved control of the vehicle while stopping. Vehi-
cle stopping distance is still dependent on vehicle
speed, weight, tires, road surfaces and other factors.
Though ABS provides the driver with some steer-
ing control during hard braking, there are conditions
however, where the system does not provide any ben-
efit. In particular, hydroplaning is still possible when
the tires ride on a film of water. This results in the
vehicles tires leaving the road surface rendering the
vehicle virtually uncontrollable. In addition, extremesteering maneuvers at high speed or high speed cor-
nering beyond the limits of tire adhesion to the road
surface may cause vehicle skidding, independent of
vehicle braking. For this reason, the ABS system is
termed Antilock instead of Anti-Skid.
NOISE AND BRAKE PEDAL FEEL
During ABS braking, some brake pedal movement
may be felt. In addition, ABS braking will create
ticking, popping and/or groaning noises heard by the
driver. This is normal due to pressurized fluid being
transferred between the master cylinder and the
brakes. If ABS operation occurs during hard braking,
some pulsation may be felt in the vehicle body due to
fore and aft movement of the suspension as brake
pressures are modulated.
At the end of an ABS stop, ABS will be turned off
when the vehicle is slowed to a speed of 3±4 mph.
There may be a slight brake pedal drop anytime that
the ABS is deactivated, such as at the end of the stop
when the vehicle speed is less then 3 mph or during
an ABS stop where ABS is no longer required. These
conditions will exist when a vehicle is being stopped
on a road surface with patches of ice, loose gravel or
sand on it. Also stopping a vehicle on a bumpy road
surface will activate ABS because of the wheel hop
caused by the bumps.
TIRE NOISE AND MARKS
Although the ABS system prevents complete wheel
lock-up, some wheel slip is desired in order to
achieve optimum braking performance. Wheel slip is
defined as follows, 0 percent slip means the wheel is
rolling freely and 100 percent slip means the wheel is
fully locked. During brake pressure modulation,
wheel slip is allowed to reach up to 25 to30%. This
means that the wheel rolling velocity is 25 to 30%
less than that of a free rolling wheel at a given vehi-
cle speed. This slip may result in some tire chirping,
depending on the road surface. This sound should not
be interpreted as total wheel lock-up.
Complete wheel lock up normally leaves black tire
marks on dry pavement. The ABS System will not
leave dark black tire marks since the wheel never
reaches a fully locked condition. Tire marks may
however be noticeable as light patched marks.
START UP CYCLE
When the ignition is turned on, a popping sound
and a slight brake pedal movement may be noticed.
Additionally, when the vehicle is first driven off a
humming may be heard and/or felt by the driver at
approximately 20 to 40 kph (12 to 25 mph). The ABS
warning lamp will also be on for up to 5 seconds
after the ignition is turned on. All of these conditions
are a normal function of ABS as the system is per-
forming a diagnosis check.
5 - 86 BRAKESNS
DESCRIPTION AND OPERATION (Continued)

The primary functions of the (CAB) are:
(1) Detect wheel locking or wheel slipping tenden-
cies by monitoring the speed of all four wheels of the
vehicle.
(2) Illuminate the TRAC lamp in the message cen-
ter on the instrument panel when a traction control
event is occurring.
(3) Control fluid modulation to the wheel brakes
while the system is in an ABS mode or the traction
control system is activated.
(4) Monitor the system for proper operation.
(5) Provide communication to the DRB Scan Tool
while in diagnostic mode.
(6) Store diagnostic information.
(7)The CAB continuously communicates with
the body controller by sending out a message to
the body controller on the CCD Bus. This mes-
sage is used for illumination of the yellow
antilock warning lamp. This is used if the ABS
controller communication is lost in the hard
wire between the body controller and the yel-
low antilock warning lamp. If the body control-
ler does not receive this message from the CAB,
the body controller will illuminate the antilock
yellow warning lamp.
The CAB continuously monitors the speed of each
wheel through the signals generated by the wheel
speed sensors to determine if any wheel is beginning
to lock. When a wheel locking tendency is detected,
the CAB commands the CAB command coils to actu-
ate. The CAB command coils then open and close the
valves in the HCU which modulate brake fluid pres-
sure in some or all of the hydraulic circuits. The CAB
continues to control pressure in individual hydraulic
circuits until a locking tendency is no longer present.
The ABS system is constantly monitored by the
CAB for proper operation. If the CAB detects a fault,
it will turn on the Amber ABS Warning Lamp anddisable the ABS braking system. The normal base
braking system will remain operational.
The CAB contains a self-diagnostic program which
will turn on the Amber ABS Warning Lamp when a
ABS system fault is detected. Faults are then stored
in a diagnostic program memory. There are multiple
fault messages which may be stored in the CAB and
displayed through the DRB Scan Tool. These fault
messages will remain in the CAB memory even after
the ignition has been turned off. The fault messages
can be read and or cleared from the CAB memory by
a technician using the DRB Scan Tool. The fault
occurrence and the fault code will also be automati-
cally cleared from the CAB memory after the identi-
cal fault has not been seen during the next 3500
miles of vehicle operation. Mileage though of the last
fault occurrence will not be automatically cleared.CONTROLLER ANTILOCK BRAKE INPUTS
²Four wheel speed sensors.
²Stop lamp switch.
²Ignition switch.
²System relay voltage.
²Ground.
²Traction Control Switch (If Equipped).
²Diagnostics Communications (CCD)
CONTROLLER ANTILOCK BRAKE OUTPUTS
²C2D Communication To Body Controller And
Instrument Cluster
²ABS warning lamp actuation.
²Traction Control Light (If Equipped).
²Diagnostic communication. (CCD)
ABS WARNING LAMP (YELLOW)
The ABS system uses a yellow colored ABS Warn-
ing Lamp. The ABS warning lamp is located on the
right side of the message center located at the top of
the instrument panel. The purpose of the warning
lamp is discussed in detail below.
The ABS warning lamp will turn on when the CAB
detects a condition which results in a shutdown of
ABS function or when the body controller does not
receive C2D messages from the CAB. When the igni-
tion key is turned to the on position, the ABS Warn-
ing Lamp is on until the CAB completes its self tests
and turns the lamp off (approximately 4 seconds
after the ignition switch is turned on). Under most
conditions, when the ABS warning lamp is on, only
the ABS function of the brake system is affected. The
standard brake system and the ability to stop the car
will not be affected when only the ABS warning lamp
is on.
The ABS warning lamp is controlled by the CAB
and the body controller through a diode located in
the wiring harness junction block. The junction block
is located under the instrument panel to the left of
Fig. 10 Controller Antilock Brake (CAB)
NSBRAKES 5 - 91
DESCRIPTION AND OPERATION (Continued)

these inputs to the CAB should be investigated if a
complaint of intermittent warning system operation
is encountered.
(12) Low system voltage. If Low System Voltage is
detected by the CAB, the CAB will turn on the ABS
Warning Lamp until normal system voltage is
achieved. Once normal voltage is seen at the CAB,
normal operation resumes.
(13) High system voltage. If high system voltage is
detected by the CAB, the CAB will turn on the
Amber ABS Warning Lamp until normal system volt-
age is achieved. Once normal voltage is again
detected by the CAB, normal ABS operation will be
resumed at the next key on cycle.
(14) Additionally, any condition which results in
interruption of electrical current to the CAB or mod-
ulator assembly may cause the ABS Warning Lamp
to turn on intermittently.
(15) The body controller can turn on the (yellow)
ABS warning lamp if CCD communication between
the body controller and the CAB is interupted.
TONEWHEEL INSPECTION
CAUTION: The tone wheels used on this vehicle
equipped with the Teves Mark 20 Antilock Brake
System are different then those used on past mod-
els of this vehicle equipped with antilock brakes.
Reduced braking performance will result if this part
is used on earlier model vehicles and an accident
could result. Do not use on pre-1998 model year
vehicles.
Carefully inspect tonewheel at the suspected faulty
wheel speed sensor for missing, chipped or broken
teeth, this can cause erratic speed sensor signals.
Tonewheels should show no evidence of contact
with the wheel speed sensors. If contact was made,
determine cause and correct before replacing the
wheel speed sensor.
Excessive runout of the tonewheel can cause
erratic wheel speed sensor signals. Refer to Tone-
wheel Runout in the Specification Section in this sec-
tion of the service manual for the tonewheel runout
specification. Replace drive shaft assembly or rear
hub/bearing assembly if tonewheel runout exceeds
the specification.
Inspect tonewheels for looseness on their mounting
surfaces. Tonewheels are pressed onto their mounting
surfaces and should not rotate independently from
the mounting surface.
Check the wheel speed sensor head alignment to
the tone wheel. Also check the gap between the speed
sensor head and the tone wheel to ensure it is at
specification. Refer to Wheel Speed Sensor Clearance
in the Specification Section in this section of the ser-
vice manual.
PROPORTIONING VALVE
CAUTION: Proportioning valves (Fig. 18) should
never be disassembled.
If premature rear wheel skid occurs on hard brake
application, it could be an indication that a malfunc-
tion has occurred with one of the proportioning
valves.
If a malfunctioning proportioning valve is sus-
pected on a vehicle, refer to Proportioning Valve Test
in the Proportioning Valves Section in this group of
the service manual for the required test procedure.
BRAKE FLUID CONTAMINATION
Indications of fluid contamination are swollen or
deteriorated rubber parts.
Swollen rubber parts indicate the presence of
petroleum in the brake fluid.
To test for contamination, put a small amount of
drained brake fluid in clear glass jar. If fluid sepa-
rates into layers, there is mineral oil or other fluid
contamination of the brake fluid.
If brake fluid is contaminated, drain and thor-
oughly flush system. Replace master cylinder, propor-
tioning valve, caliper seals, wheel cylinder seals,
Antilock Brakes hydraulic unit and all hydraulic
fluid hoses.
TEST DRIVING ABS COMPLAINT VEHICLE
Most ABS complaints will require a test drive as a
part of the diagnostic procedure. The purpose of the
test drive is to duplicate the condition.
NOTE: Remember conditions that result in the
turning on of the Red BRAKE Warning Lamp may
indicate reduced braking ability. The following pro-
cedure should be used to test drive an ABS com-
plaint vehicle.
Fig. 18 Brake Proportioning Valve Identification
5 - 98 BRAKESNS
DIAGNOSIS AND TESTING (Continued)

RADIATOR COOLANT FLOW TEST
To determine whether coolant is flowing through
the cooling system, use the following procedure:
(1) If engine is cold, idle engine until normal oper-
ating temperature is reached. Then feel the upper
radiator hose. If it is hot, coolant is circulating.
WARNING: DO NOT REMOVE RADIATOR PRES-
SURE CAP WITH THE SYSTEM HOT AND UNDER
PRESSURE BECAUSE SERIOUS BURNS FROM
COOLANT CAN OCCUR.
(2) Remove radiator pressure cap when engine is
cold, idle engine until thermostat opens, you should
observe coolant flow while looking down the filler
neck. Once flow is detected install radiator pressure
cap.
RADIATOR FAN CONTROL
Fan control is accomplished two ways. A pressure
transducer on the compressor discharge line sends a
signal to the Powertrain Control Module (PCM)
which will activate the fan. In addition to this con-
trol, the fan is turned on by the temperature of the
coolant which is sensed by the coolant temperature
sensor which sends the message to the PCM. The fan
will not run during cranking until the engine starts
no matter what the coolant temperature is.
CAUTION: The solid state fan relay is attached to
the left frame rail near the lower radiator support.
The relay bracket, and fastener are used to dissi-
pate heat from the relay. Ensure the relay is prop-
erly attached to prevent the following:
²Intermittent engine overheating.
²Relay ªthermalº shutdown, or relay damage.
ELECTRIC FAN MOTOR TEST
Refer to Powertrain Diagnostic Manual for proce-
dure.
TESTING COOLING SYSTEM FOR LEAKS
With engine not running, wipe the radiator filler
neck sealing seat clean. The radiator should be full.
Attach the Radiator Pressure Tool to the radiator,
as shown in (Fig. 12) and apply 104 kPa (15 psi)
pressure. If the pressure drops more than 2 psi in 2
minutes, inspect all points for external leaks.
All radiator and heater hoses should be shaken
while at 104 kPa (15 psi), since some leaks occur only
while driving due to engine movement.
If there are no external leaks, after the gauge dial
shows a drop in pressure, detach the tester. Start
engine and run the engine up to normal operating
temperature to open the thermostat and allow the
coolant to expand. Reattach the tester. If the needleon the dial fluctuates it indicates a combustion leak,
usually a head gasket leak.
RADIATOR FAN OPERATION
Radiator Fan Control A/C Pressure
Fan
Operation
Low
Fan
Speed
30%High
Fan
Speed
100%Low
Fan
Speed
30%High
Fan
Speed
100%
On: 104ÉC
(220ÉF)110ÉC
(230ÉF)
Fan
Speed
Duty-
Cycles
(Ramps-
up) from
31% to
99%1,724
Kpa
(250
psi)2,068
Kpa
(300
psi)Fan
Speed
Duty-
Cycles
(Ramps-
up) from
31% to
99%
Off: 101ÉC
(214ÉF)Fan
Speed
Duty-
Cycles
(Ramps-
down)
from
99% to
31%1,710
Kpa
(248
psi)Fan
Speed
Duty-
Cycles
(Ramps-
down)
from
99% to
31%
Fig. 12 Pressure Testing Cooling System
7 - 14 COOLING SYSTEMNS
DIAGNOSIS AND TESTING (Continued)

Clean Spark Plug cables with a cloth moistened
with a non-flammable solvent. Wipe the cables dry.
Check for brittle or cracked insulation.
SPARK PLUG CABLESÐ3.3/3.8L
The spark plug cables and spark plug boots are
made from high temperature silicone materials. The
spark plug boots utilize metal heat shields for ther-
mal protection from the exhaust manifold. The heat
shields slide over the spark plug boots. The notches
on the heat shields ensure the spark plug boot and
shield twist together during spark plug boot removal.
They also identify proper heat shield installation on
the boot for service.Refer to 3.3/3.8L Spark Plug
Cable removal and installation.All spark plug
cable leads are properly identified with cylinder num-
bers. The inside of the spark plug boot is coated with
a special high temperature silicone grease for greater
sealing and to minimize boot bonding to the spark
plug insulator. The convoluted tubing on the rear
plug cables are made of a high temperature plastic
material. Under normal driving conditions, the spark
plug cables have a recommended service life of a
100,000 miles. The spark plugs have a recommended
service life of 75,000 miles for severe driving condi-
tions per schedule B in this manual.
The spark plug heat shield can be reused if an
ignition cable is replaced due to failure. Never reuse
heat shield's that have heat shield anti-twist, side or
spark plug attachment tabs bent or missing. Ensure
that the heat shield is properly attached to the spark
plug to avoid RFI problems. The bottom of the spark
plug heat shield must make contact with the spark
plug hex.
The front ignition cables must not make contact
with the oil dip stick tube and #5 cable must not
touch the coil mounting bolt to avoid abrasion/dielec-
tric failures.
IGNITION COIL
WARNING: THE DIRECT IGNITION SYSTEM GEN-
ERATES APPROXIMATELY 40,000 VOLTS. PER-
SONAL INJURY COULD RESULT FROM CONTACT
WITH THIS SYSTEM.
The ignition coil assembly consists of 3 indepen-
dent coils molded together (Fig. 4). The coil assembly
is mounted on the intake manifold. Spark plug cables
route to each cylinder from the coil. The coil fires two
spark plugs every power stroke. One plug is the cyl-
inder under compression, the other cylinder fires on
the exhaust stroke. The Powertrain Control Module
(PCM) determines which of the coils to charge and
fire at the correct time.
Coil 1 fires cylinders 1 and 4, coil 2 fires cylinders
2 and 5, coil 3 fires cylinders 3 and 6.The Auto Shutdown (ASD) relay provides battery
voltage to the ignition coil. The PCM provides a
ground contact (circuit) for energizing the coil. When
the PCM breaks the contact, the energy in the coil
primary transfers to the secondary causing the
spark. The PCM will de-energize the ASD relay if it
does not receive the crankshaft position sensor and
camshaft position sensor inputs. Refer to Auto Shut-
down (ASD) RelayÐPCM Output, in this section for
relay operation.
AUTOMATIC SHUTDOWN (ASD) RELAY
The Powertrain Control Module (PCM) operates
the Auto Shutdown (ASD) relay by switching the
ground path on and off.
The ASD relay supplies battery voltage to the fuel
injectors, electronic ignition coil and the heating ele-
ments in the oxygen sensors.
The PCM controls the relay by switching the
ground path for the solenoid side of the relay on and
off. The PCM turns the ground path off when the
ignition switch is in the Off position unless the 02
Heater Monitor test is being run. Refer to Group 25,
On-Board Diagnostics. When the ignition switch is in
the On or Crank position, the PCM monitors the
crankshaft position sensor and camshaft position sen-
sor signals to determine engine speed and ignition
timing (coil dwell). If the PCM does not receive the
crankshaft position sensor and camshaft position sen-
sor signals when the ignition switch is in the Run
position, it will de-energize the ASD relay.
The ASD relay is located in the Power Distribution
Center (PDC). The PDC is located on the driver's
side inner fender well (Fig. 5). A label on the under-
side of the PDC cover identifies the relays and fuses
in the PDC.
Fig. 4 Ignition Coil Pack
8D - 4 IGNITION SYSTEMNS
GENERAL INFORMATION (Continued)

(3) Remove ignition cables from the secondary tow-
ers of the coil. Measure the secondary resistance of
the coil between the towers of each individual coil
(Fig. 21). Secondary resistance should be 7,000 to
15,800 ohms. Replace the coil if resistance is not
within tolerance.
FAILURE TO START TEST
This no-start test checks the camshaft position sen-
sor and crankshaft position sensor.
The Powertrain Control Module (PCM) supplies 8
volts to the camshaft position sensor and crankshaft
position sensor through one circuit. If the 8 volt sup-
ply circuit shorts to ground, neither sensor will pro-
duce a signal (output voltage to the PCM).
When the ignition key is turned and left in the On
position, the PCM automatically energizes the Auto
Shutdown (ASD) relay. However, the controller de-en-
ergizes the relay within one second because it has
not received a camshaft position sensor signal indi-
cating engine rotation.
During cranking, the ASD relay will not energize
until the PCM receives a camshaft position sensor
signal. Secondly, the ASD relay remains energized
only if the controller senses a crankshaft position
sensor signal immediately after detecting the cam-
shaft position sensor signal.
(1) Check battery voltage. Voltage should be
approximately 12.66 volts or higher to perform fail-
ure to start test.
(2) Disconnect the harness connector from the coil
pack.
(3) Connect a test light to the B+ (battery voltage)
terminal of the coil electrical connector and ground
as shown in (Fig. 22). The B+ wire for the DIS coil is
dark green with an orange tracer.Do not spread
the terminal with the test light probe.(4) Turn the ignition key to theON position.The
test light should flash On and then Off.Do not turn
the Key to off position, leave it in the On posi-
tion.
(a) If the test light flashes momentarily, the
PCM grounded the Auto Shutdown (ASD) relay.
Proceed to step 5.
(b) If the test light did not flash, the ASD relay
did not energize. The cause is either the relay or
one of the relay circuits. Use the DRB scan tool to
test the ASD relay and circuits. Refer to the appro-
priate Powertrain Diagnostics Procedure Manual.
Refer to the wiring diagrams section for circuit
information.
(5) Crank the engine. (If the key was placed in the
off position after step 4, place the key in the On posi-
tion before cranking. Wait for the test light to flash
once, then crank the engine.)
(6) If the test light momentarily flashes during
cranking, the PCM is not receiving a crankshaft posi-
tion sensor signal. Use the DRB scan tool to test the
crankshaft position sensor and sensor circuits. Refer
to the appropriate Powertrain Diagnostics Procedure
Manual. Refer to the wiring diagrams section for cir-
cuit information.
(7) If the test light did not flash during cranking,
unplug the crankshaft position sensor connector.
Turn the ignition key to the off position. Turn the
key to the On position, wait for the test light to
momentarily flash once, then crank the engine. If the
test light momentarily flashes, the crankshaft posi-
tion sensor is shorted and must be replaced. If the
light did not flash, the cause of the no-start is in
Fig. 21 Checking Ignition Coil Secondary
ResistanceFig. 22 Ignition Coil Engine Harness Connector
8D - 10 IGNITION SYSTEMNS
DIAGNOSIS AND TESTING (Continued)

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)