2004 CHRYSLER VOYAGER wheel

INSTALLATION - PARKING BRAKE CABLE
(LEFT REAR)
(1) Install the rear parking brake cable in the
brake support plate. Insert cable housing retainer
into brake support plate making certain that cable
housing retainer fingers lock the housing and
retainer firmly into place.
(2) Attach the parking brake cable onto the park
brake actuator lever.
(3) Install the brake shoes on the rear brake sup-
port plate. (Refer to 5 - BRAKES/HYDRAULIC/ME-
CHANICAL/BRAKE PADS/SHOES -
INSTALLATION).
(4) Insert cable housing retainer into body outrig-
ger bracket making certain that cable housing
retainer fingers lock the housing firmly into place.
(5) Connect rear parking brake cable to the equal-
izer bracket (Fig. 99).
(6) Install brake drum, and wheel and tire assem-
bly.
(7) Remove the locking pliers from the front park
brake cable. This will automatically adjust the park
brake cables.
(8) Apply and release park brake pedal 1 time.
This will seat the park brake cables.
ADJUSTMENTS
ADJUSTMENT - PARKING BRAKE CABLES
The park brake cables on this vehicle have an
automatic self adjuster built into the park brake
pedal mechanism. When the foot operated park brake
pedal is in its released (upward most) position, a
clock spring automatically adjusts the park brake
cables. The park brake cables are adjusted (ten-
sioned) just enough to remove all the slack from the
cables. The automatic adjuster system will not over
adjust the cables causing rear brake drag.
Due to the automatic adjust feature of the park
brake pedal, adjustment of the parking brake cables
on these vehicles relies on proper drum brake and
park brake shoe adjustment. (Refer to 5 - BRAKES/
HYDRAULIC/MECHANICAL/DRUM - ADJUST-
MENTS) and (Refer to 5 - BRAKES/PARKING
BRAKE/SHOES - ADJUSTMENTS).
When the park brake pedal is applied the self
adjuster is by-passed and the pedal operates nor-
mally to engage the park brakes.
When a service procedure needs to be performed on
the park brake pedal or the park brake cables, the
automatic self adjuster can be manually locked out
by the service technician.
CABLES - PARKING BRAKE
(EXPORT)
REMOVAL - FRONT CABLE
(Refer to 5 - BRAKES - BASE/PARKING BRAKE/
LEVER - REMOVAL)
INSTALLATION - FRONT CABLE
(Refer to 5 - BRAKES - BASE/PARKING BRAKE/
LEVER - INSTALLATION)
LEVER - PARKING BRAKE
REMOVAL
(1) Manually release the automatic self-adjusting
mechanism tension of the parking brake lever (pedal)
assembly. (Refer to 5 - BRAKES/PARKING BRAKE -
STANDARD PROCEDURE).
(2) Disconnect negative (ground) cable from the
battery and isolate cable from battery terminal.
(3) Remove sill scuff plate from left door sill.
(4) Remove the left side kick panel.
(5) Remove the silencer panel under the instru-
ment panel.
(6) Remove the steering column cover from the
lower instrument panel.
(7) Remove the reinforcement from the lower
instrument panel.
(8) Remove the front parking brake cable from the
parking brake cable equalizer (Fig. 102).
(9) Remove tension from front park brake cable.
Tension is removed by releasing the locking pliers
from the front park brake cable.
Fig. 102 Parking Brake Cable Equalizer
1 - EQUALIZER
2 - LEFT REAR PARKING BRAKE CABLE
3 - LOCKING NUT
4 - INTERMEDIATE PARKING BRAKE CABLE
5 - FRONT PARKING BRAKE CABLE
5 - 64 BRAKES - BASERS
CABLES - PARKING BRAKE (Continued)

the park brake in this position, install a pair of lock-
ing pliers on the front parking brake cable just rear-
ward of the second body outrigger bracket.
(11) Install the equalizer on the front parking
brake cable and install the left rear and intermediate
park brake cable in the correct location on the park-
ing brake cable equalizer (Fig. 105).
(12) Remove the locking pliers from the front park-
ing brake cable. This will allow the adjuster in the
park brake lever mechanism to tension the parking
brake cables.
(13) Lower the vehicle.
(14) Apply and release the parking brake lever one
time. This will seat the parking brake cables and
allow the auto adjuster in the parking brake lever
mechanism to correctly tension the parking brake
cables.
SHOES - PARKING BRAKE
REMOVAL
(1) AWD only - Set the parking brake.The park-
ing brake is set to keep the hub/bearing and
axle shaft from rotating when loosening the
hub nut.
(2) Raise vehicle. (Refer to LUBRICATION &
MAINTENANCE/HOISTING - STANDARD PROCE-
DURE).
(3) Remove the wheel and tire assembly.
(4) AWD only - Remove the cotter pin and nut
retainer (Fig. 106) from the stub shaft of the outer
C/V joint.(5) AWD only - Remove the spring washer (Fig.
107) from the stub shaft of the outer C/V joint.
(6) AWD only - Remove the hub nut and washer
(Fig. 108) from the stub shaft of the outer C/V joint.
(7) Release the parking brake.
(8) Create slack in the rear park brake cables by
locking the out the automatic adjuster as described.
Grasp the exposed section of front park brake cable
and pull downward on it. Then install a pair of lock-
ing pliers on the front park brake cable just rearward
of the second body outrigger bracket (Fig. 109).
Fig. 106 Cotter Pin And Nut Retainer
1 - CALIPER
2 - COTTER PIN
3 - ROTOR
4 - NUT RETAINER
5 - OUTER C/V JOINT
Fig. 107 Spring Washer
1 - HUB NUT
2 - STUB SHAFT
3 - ROTOR
4 - SPRING WASHER
Fig. 108 Hub Nut And Washer
1 - CALIPER
2 - HUB NUT
3 - WASHER
4 - ROTOR
5 - ADAPTER
RSBRAKES - BASE5-67
LEVER - PARKING BRAKE (EXPORT) (Continued)

(12) Remove the rotor from the hub/bearing.
(13) Remove the park brake cable mounting bolt to
adapter.
(14) Remove the end of the park brake cable from
the actuator lever on the adapter (Fig. 113).
(15) Remove the end of the park brake cable from
the adapter. Park brake cable is removed from
adapter using a 1/2 wrench slipped over the park
brake cable retainer as show in (Fig. 114) to com-
press the locking tabs on the park brake cable
retainer.(16) AWD only - Remove ABS wheel speed sensor
head from hub/bearing (Fig. 115).
(17) FWD only - Remove the ABS wheel speed sen-
sor from the hub/bearing in the following fashion:
(a) Remove secondary (yellow) retaining clip at
rear of wheel speed sensor head (Fig. 116).
(b) Push up on metal retaining clip (Fig. 116)
until it bottoms. This will release wheel speed sen-
sor head from hub and bearing. While holding
metal clip up, pull back on wheel speed sensor
head removing it from hub and bearing.
(c) Remove wheel speed sensor from hub/bear-
ing.
Fig. 113 Park Brake Cable Attachment To Actuator
1 - ADAPTER
2 - PARK BRAKE CABLE
3 - ACTUATOR
4 - AXLE
5 - DRIVESHAFT
6 - PARK BRAKE CABLE RETAINER
7 - HORSESHOE CLIP
Fig. 114 Park Brake Cable Removal From Adapter
1 - DRIVESHAFT
2 - 1/2º WRENCH
3 - PARK BRAKE CABLE
4 - PARK BRAKE CABLE RETAINER
5 - ADAPTER
Fig. 115 Speed Sensor Attaching Bolt (AWD)
1 - ADAPTER
2 - TONE WHEEL
3 - WHEEL SPEED SENSOR
4 - AXLE
5 - BOLT
6 - DRIVESHAFT
Fig. 116 Sensor Connection At Hub And Bearing
1 - SECONDARY SENSOR RETAINING CLIP
2 - METAL SENSOR RETAINING CLIP
3 - HUB AND BEARING
RSBRAKES - BASE5-69
SHOES - PARKING BRAKE (Continued)

(13) AWD only - Install the wheel speed sensor on
the hub/bearing and adapter. Install the wheel speed
sensor attaching bolt (Fig. 115). Tighten the wheel
speed sensor attaching bolt to a torque of 12 N´m
(105 in. lbs).
(14) FWD only - Install the wheel speed sensor in
the following fashion:
(a) If metal wheel speed sensor retaining clip is
not in the neutral installed position on hub and
bearing cap, install from the bottom, if necessary,
and push clip upward until it snaps into position.
(b) Install wheel speed sensor head into rear of
hub and bearing aligning index tab with the notch
in the top of the mounting hole. Push the sensor in
until it snaps into place on the metal retaining
clip.
(c) Install secondary (yellow) retaining clip over
wheel speed sensor head and engage the tabs on
each side.
(15) Install the park brake cable into its mounting
hole in the adapter.Be sure all the locking tabs
on the park brake cable retainer are expanded
out to ensure the cable will not pull out of the
adapter.
(16) Install the end of the park brake cable on the
park brake actuator lever (Fig. 113).
(17) Attach park brake cable to adapter using
mounting bolt.
(18) Remove the locking pliers (Fig. 109) from the
front park brake cable.
(19) Adjust the park brake drum-in-hat brake
shoes. (Refer to 5 - BRAKES/PARKING BRAKE/
SHOES - ADJUSTMENTS).
(20) Install the rotor on the hub/bearing.
(21) Carefully lower caliper and brake shoes over
rotor and onto the adapter using the reverse proce-
dure for removal (Fig. 111).
CAUTION: When installing guide pin bolts extreme
caution should be taken not to crossthread the cal-
iper guide pin bolts.
(22) Install the caliper guide pin bolts (Fig. 110).
Tighten the guide pin bolts to a torque of 35 N´m (26
ft. lbs.).
(23) AWD only - Clean all foreign material off the
threads of the outer C/V joint stub shaft. Install the
washer and hub nut (Fig. 108) on the stub shaft of
the outer C/V joint.
(24) AWD only - Set the parking brake.
(25) AWD only - Tighten the hub nut to a torque of
244 N´m (180 ft. lbs.).
(26) AWD only - Install the spring washer (Fig.
107) on the stub shaft of the outer C/V joint.
(27) AWD only - Install the nut retainer and cotter
pin (Fig. 106) on the stub shaft of the outer C/V joint.(28) Install the wheel and tire assembly. Tighten
the wheel mounting stud nuts in proper sequence
until all nuts are torqued to half specification. Then
repeat the tightening sequence to the full specified
torque of 135 N´m (100 ft. lbs.).
(29) Lower vehicle.
(30) Fully apply and release the park brake pedal
one time. This will seat and correctly adjust the park
brake cables.
CAUTION: Before moving vehicle, pump the brake
pedal several times to insure the vehicle has a firm
brake pedal to adequately stop vehicle.
(31) Road test the vehicle and make several stops
to wear off any foreign material on the brakes and to
seat the brake shoe linings.
ADJUSTMENTS
ADJUSTMENT - PARKING BRAKE SHOES
CAUTION: Before adjusting the park brake shoes be
sure that the park brake pedal is in the fully
released position. If park brake pedal is not in the
fully released position, the park brake shoes can
not be accurately adjusted.
(1) Raise vehicle.
(2) Remove tire and wheel.
(3) Remove disc brake caliper from caliper adapter
(Fig. 128). (Refer to 5 - BRAKES/HYDRAULIC/ME-
CHANICAL/DISC BRAKE CALIPERS - REMOVAL).
(4) Remove rotor from hub/bearing.
Fig. 128 Disc Brake Caliper
1 - DISC BRAKE CALIPER
2 - ADAPTER
3 - AXLE
4 - GUIDE PIN BOLTS
5 - DRIVESHAFT (AWD MODELS ONLY)
RSBRAKES - BASE5-73
SHOES - PARKING BRAKE (Continued)

NOTE: When measuring the brake drum diameter,
the diameter should be measured in the center of
the area in which the park brake shoes contact the
surface of the brake drum.
(5) Using Brake Shoe Gauge, Special Tool C-3919,
or equivalent,accuratelymeasure the inside diam-
eter of the park brake drum portion of the rotor (Fig.
129).
(6) Using a ruler that reads in 64th of an inch,
accurately read the measurement of the inside diam-
eter of the park brake drum from the special tool
(Fig. 130).
(7) Reduce the inside diameter measurement of
the brake drum that was taken using Special Tool
C-3919 by 1/64 of an inch. Reset Gauge, Brake Shoe,
Special Tool C-3919 or the equivalent used, so that
the outside measurement jaws are set to the reduced
measurement (Fig. 131).(8) Place Gauge, Brake Shoe, Special Tool C-3919,
or equivalent over the park brake shoes. The special
tool must be located diagonally across at the top of
one shoe and bottom of opposite shoe (widest point)
of the park brake shoes.
(9) Using the star wheel adjuster, adjust the park
brake shoes until the lining on the park brake shoes
just touches the jaws on the special tool.
(10) Repeat step 8 above and measure shoes in
both directions.
(11) Install brake rotor on hub and bearing.
(12) Rotate rotor to verify that the park brake
shoes are not dragging on the brake drum. If park
brake shoes are dragging, remove rotor and back off
star wheel adjuster one notch and recheck for brake
shoe drag against drum. Continue with the previous
step until brake shoes are not dragging on brake
drum.
(13) Install disc brake caliper on caliper adapter
(Fig. 128). (Refer to 5 - BRAKES/HYDRAULIC/ME-
CHANICAL/DISC BRAKE CALIPERS - INSTALLA-
TION).
(14) Install wheel and tire.
(15) Tighten the wheel mounting nuts in the
proper sequence until all nuts are torqued to half the
specified torque. Then repeat the tightening sequence
to the full specified torque of 129 N´m (95 ft. lbs.).
(16) Lower vehicle.
(17) Apply and release the park brake pedal one
time. This will seat and correctly adjust the park
brake cables.
CAUTION: Before moving vehicle, pump brake
pedal several times to ensure the vehicle has a firm
enough pedal to stop the vehicle.
(18) Road test the vehicle to ensure proper func-
tion of the vehicle's brake system.
Fig. 129 Measuring Park Brake Drum Diameter
Fig. 130 Reading Park Brake Drum Diameter
1 - SPECIAL TOOL C-3919
2 - RULER
Fig. 131 Setting Gauge To Park Brake Shoe
Measurement
1 - RULER
2 - SPECIAL TOOL C-3919
5 - 74 BRAKES - BASERS
SHOES - PARKING BRAKE (Continued)

BRAKES - ABS
TABLE OF CONTENTS
page page
BRAKES - ABS
DESCRIPTION
DESCRIPTION - ANTILOCK BRAKE
SYSTEM............................75
DESCRIPTION - ANTILOCK BRAKE
SYSTEM (EXPORT)....................75
DESCRIPTION - ELECTRONIC VARIABLE
BRAKE PROPORTIONING...............75
DESCRIPTION - TRACTION CONTROL
SYSTEM............................76
OPERATION
OPERATION - ANTILOCK BRAKE SYSTEM . . 76
OPERATION - ELECTRONIC VARIABLE
BRAKE PROPORTIONING...............77
OPERATION - TRACTION CONTROL
SYSTEM............................77
CAUTION
CAUTIONS..........................78
STANDARD PROCEDURE - ANTILOCK BRAKE
SYSTEM BLEEDING...................78
SPECIFICATIONS
ABS FASTENER TORQUE...............79
TONE WHEEL RUNOUT................79
WHEEL SPEED SENSOR AIR GAP........79
FRONT WHEEL SPEED SENSOR
REMOVAL.............................79
INSTALLATION.........................80
REAR WHEEL SPEED SENSOR - AWD
REMOVAL.............................80INSTALLATION.........................80
REAR WHEEL SPEED SENSOR - FWD
REMOVAL.............................81
INSTALLATION.........................81
TONE WHEEL
INSPECTION - TONE WHEEL..............82
TRACTION CONTROL SWITCH
DIAGNOSIS AND TESTING - TRACTION
CONTROL SWITCH....................82
HYDRAULIC/MECHANICAL
OPERATION - HYDRAULIC CIRCUITS AND
VALVES .............................83
HCU (HYDRAULIC CONTROL UNIT)
DESCRIPTION.........................89
OPERATION...........................89
ICU (INTEGRATED CONTROL UNIT)
DESCRIPTION.........................89
OPERATION...........................90
REMOVAL
REMOVAL - LHD......................90
REMOVAL - RHD......................91
DISASSEMBLY - ICU....................93
ASSEMBLY - ICU.......................94
INSTALLATION
INSTALLATION - LHD..................94
INSTALLATION - RHD..................95
BRAKES - ABS
DESCRIPTION
DESCRIPTION - ANTILOCK BRAKE SYSTEM
This section covers the physical and operational
descriptions and the on-car service procedures for the
Mark 20e Antilock Brake System and the Mark 20e
Antilock Brake System with traction control.
The purpose of the antilock brake system (ABS) is
to prevent wheel lockup under braking conditions on
virtually any type of road surface. Antilock braking is
desirable because a vehicle that is stopped without
locking the wheels retains directional stability and
some steering capability. This allows the driver to
retain greater control of the vehicle during braking.
DESCRIPTION - ANTILOCK BRAKE SYSTEM
(EXPORT)
Four-wheel disc antilock brakes are standard on all
models. The Mark 20e antilock brake system is used
on all models. Depending on whether the vehicle is a
left-hand drive (LHD) or right-hand drive (RHD)
model, the integrated control unit (ICU) is located in
one of two locations. On LHD models, the ICU is
mounted above the front suspension cradle/cross-
member below the master cylinder. On RHD models,
the ICU is located behind the front suspension cra-
dle/crossmember on the left side of the vehicle.
DESCRIPTION - ELECTRONIC VARIABLE
BRAKE PROPORTIONING
Vehicles equipped with ABS use electronic variable
brake proportioning (EVBP) to balance front-to-rear
braking. The EVBP is used in place of a rear propor-
RSBRAKES - ABS5-75

tioning valve. The EVBP system uses the ABS sys-
tem to control the slip of the rear wheels in partial
braking range. The braking force of the rear wheels
is controlled electronically by using the inlet and out-
let valves located in the integrated control unit
(ICU).
EVBP activation is invisible to the customer since
there is no pump motor noise or brake pedal feed-
back.
DESCRIPTION - TRACTION CONTROL SYSTEM
Traction control reduces wheel slip and maintains
traction at the driving wheels at speeds below 56
km/h (35 mph) when road surfaces are slippery. The
traction control system reduces wheel slip by braking
the wheel that is losing traction.
HYDRAULIC SHUTTLE VALVES
Two pressure relief hydraulic shuttle valves are
included on vehicles with traction control. These
valves are located inside the HCU and cannot be ser-
viced separately from the HCU.
TRACTION CONTROL LAMP
The traction control function lamp is located in the
transmission range indicator display of the instru-
ment cluster, displaying TRAC, TRAC OFF or nei-
ther depending on system mode.
The TRAC OFF lamp is controlled by a Traction
Control Off switch that is a momentary contact type
switch. The Traction Control Off switch is located on
the steering column upper shroud.
OPERATION
OPERATION - ANTILOCK BRAKE SYSTEM
There are a few performance characteristics of the
Mark 20e Antilock Brake System that may at first
seem abnormal, but in fact are normal. These char-
acteristics are described below.
NORMAL BRAKING
Under normal braking conditions, the ABS func-
tions the same as a standard base brake system with
a diagonally split master cylinder and conventional
vacuum assist.
ABS BRAKING
ABS operation is available at all vehicle speeds
above 3±5 mph. If a wheel locking tendency is
detected during a brake application, the brake system
enters 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. Wheel
lockup may be perceived at the very end of an ABS
stop and is considered normal.
During an ABS stop, the brakes hydraulic system
is still diagonally split. However, the brake system
pressure is further split into three 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).
NOISE AND BRAKE PEDAL FEEL
During ABS braking, some brake pedal movement
may be felt. In addition, ABS braking will create
ticking, popping, or groaning noises heard by the
driver. This is normal and is 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 is 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 than 3 mph or during
an ABS stop where ABS is no longer required. These
conditions 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 sur-
face activates ABS because of the wheel hop caused
by the bumps.
TIRE NOISE AND MARKS
Although the ABS system prevents complete wheel
lockup, 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±30 percent. This means
that the wheel rolling velocity is 25±30 percent less
than that of a free rolling wheel at a given vehicle
speed. This slip may result in some tire chirping,
depending on the road surface. This sound should not
be interpreted as total wheel lockup.
Complete wheel lockup normally leaves black tire
marks on dry pavement. The ABS will not leave dark
black tire marks since the wheel never reaches a
fully locked condition. However, tire marks may be
noticeable as light patched marks.
5 - 76 BRAKES - ABSRS
BRAKES - ABS (Continued)

START-UP CYCLE
When the ignition is turned on, a popping sound
and a slight brake pedal movement may be noticed.
The ABS warning lamp will also be on for up to 5
seconds after the ignition is turned on. When the
vehicle is first driven off, a humming may be heard
or felt by the driver at approximately 20±40 kph
(12±25 mph). All of these conditions are a normal
function of ABS as the system is performing a diag-
nosis check.
PREMATURE ABS CYCLING
Symptoms of premature ABS cycling include: click-
ing sounds from the solenoid valves; pump/motor
running; and pulsations in the brake pedal. Prema-
ture ABS cycling can occur at any braking rate of the
vehicle and on any type of road surface. Neither the
red BRAKE warning lamp, nor the amber ABS warn-
ing lamp, illuminate and no fault codes are stored in
the CAB.
Premature ABS cycling is a condition that needs to
be correctly assessed when diagnosing problems with
the antilock brake system. It may be necessary to use
a DRB scan tool to detect and verify premature ABS
cycling.
Check the following common causes when diagnos-
ing premature ABS cycling: damaged tone wheels;
incorrect tone wheels; damaged steering knuckle
wheel speed sensor mounting bosses; loose wheel
speed sensor mounting bolts; excessive tone wheel
runout; or an excessively large tone wheel-to-wheel
speed sensor air gap. Give special attention to these
components when diagnosing a vehicle exhibiting
premature ABS cycling.
After diagnosing the defective component, repair or
replace it as required. When the component repair or
replacement is completed, test drive the vehicle to
verify that premature ABS cycling has been cor-
rected.
OPERATION - ELECTRONIC VARIABLE BRAKE
PROPORTIONING
Upon entry into EVBP the inlet valve for the rear
brake circuit is switched on so that the fluid supply
from the master cylinder is shut off. In order to
decrease the rear brake pressure, the outlet valve for
the rear brake circuit is pulsed. This allows fluid to
enter the low pressure accumulator (LPA) in the
hydraulic control unit (HCU) resulting in a drop in
fluid pressure to the rear brakes. In order to increase
the rear brake pressure, the outlet valve is switched
off and the inlet valve is pulsed. This increases the
pressure to the rear brakes. This back-and-forth pro-
cess will continue until the required slip difference is
obtained. At the end of EVBP braking (brakes
released) the fluid in the LPA drains back to themaster cylinder by switching on the outlet valve and
draining through the inlet valve check valve. At the
same time the inlet valve is switched on in case of
another brake application.
The EVBP will remain functional during many
ABS fault modes. If both the red BRAKE and amber
ABS warning indicators are illuminated, the EVBP
may not be functioning.
OPERATION - TRACTION CONTROL SYSTEM
The traction control module monitors wheel speed.
During acceleration, if the module detects front
(drive) wheel slip and the brakes are not applied, the
module enters traction control mode. Traction control
operation proceeds in the following order:
(1) Close the normally open isolation valves.
(2) Start the pump/motor and supply volume and
pressure to the front (drive) hydraulic circuit. (The
pump/motor runs continuously during traction con-
trol operation.)
(3) Open and close the build and decay valves to
maintain minimum wheel slip and maximum trac-
tion.
The cycling of the build and decay valves during
traction control is similar to that during antilock
braking, except the valves work to control wheel spin
by applying the brakes, whereas the ABS function is
to control wheel skid by releasing the brakes.
If the brakes are applied at anytime during a trac-
tion control cycle, the brake lamp switch triggers the
controller to switch off traction control.
HYDRAULIC SHUTTLE VALVES
Two pressure relief hydraulic shuttle valves allow
pressure and volume to return to the master cylinder
reservoir when not consumed by the build and decay
valves. These valves are necessary because the
pump/motor supplies more volume than the system
requires.
TRACTION CONTROL LAMP
The traction control system is enabled at each igni-
tion cycle. It may be turned off by depressing the
Traction Control Off switch button when the ignition
is in the ON position. The traction control function
lamp (TRAC OFF) illuminates immediately upon
depressing the button.
The traction control function lamp illuminates dur-
ing a traction control cycle, displaying TRAC.
If the CAB calculates that the brake temperatures
are high, the traction control system becomes inoper-
ative until a time-out period has elapsed. During this
ªthermo-protection mode,º the traction control func-
tion lamp illuminates TRAC OFF; note that no trou-
ble code is registered.
RSBRAKES - ABS5-77
BRAKES - ABS (Continued)