speed sensor CHRYSLER VOYAGER 2002 User Guide

(19) Road test vehicle to ensure proper operation
of the brake system.
JOUNCE BUMPER
DESCRIPTION
There are two jounce bumpers used in the rear
suspension. One mounts to each frame rail above the
rear axle.
OPERATION
The jounce bumper limits suspension travel and
metal-to-metal contact of the rear axle with the
frame under full jounce conditions.
REMOVAL
REMOVAL - AWD AND HEAVY DUTY
(1) Using slip-joint pliers grasp the base of the
jounce bumper. Turn the base counterclockwise (Fig.
20).
(2) Remove the jounce bumper from the frame rail.
REMOVAL - FRONT-WHEEL-DRIVE
(1) Remove the bolt attaching the jounce bumper
to frame rail (Fig. 21).
(2) Remove the jounce bumper from the frame rail.
INSTALLATION
INSTALLATION - AWD AND HEAVY DUTY
(1) Install jounce bumper through bumper support
plate and thread into welded nut in frame rail.
(2) Tighten the jounce bumper to 33 N´m (290 in.
lbs.) torque.
INSTALLATION - FRONT-WHEEL-DRIVE
(1) Hook the forward end of the jounce bumper
bracket in the mounting hole of the frame rail, then
install the mounting bolt in the opposite end, secur-
ing the bumper to the frame rail. Tighten the jounce
bumper mounting bolt to 33 N´m (290 in. lbs.) torque.
Fig. 19 Wheel Speed Sensor
1 - MOUNTING BOLT
2 - WHEEL SPEED SENSOR
Fig. 20 Jounce Bumper
1 - JOUNCE BUMPER
Fig. 21 Jounce Bumper - FWD
1-JOUNCE BUMPER
2 - 36 REAR SUSPENSIONRS
HUB / BEARING (Continued)
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RED BRAKE WARNING INDICATOR LAMP
CONDITION POSSIBLE CAUSES CORRECTION
RED BRAKE WARNING
LAMP ON1. Parking brake lever not fully
released.1. Release parking brake lever.
2. Parking brake warning lamp
switch on parking brake lever.2. Inspect and replace switch as necessary.
3. Brake fluid level low in reservoir. 3. Fill reservoir. Check entire system for
leaks. Repair or replace as required.
4. Brake fluid level switch. 4. Disconnect switch wiring connector. If
lamp goes out, replace switch.
5. Mechanical instrument cluster
(MIC) problem.5. Refer to appropriate Diagnostic
information.
6. Amber ABS Warning Indicator
Lamp also illuminated.6. Refer to appropriate Diagnostic
information.
BRAKE NOISE
CONDITION POSSIBLE CAUSES CORRECTION
CLICK OR SQUAWK ON
PEDAL APPLICATION1. Brake lamp switch. 1. Replace switch.
2. Brake Transmission Shift Interlock
Linkage.2. Lubricate BTSI linkage.
3. Pedal pivot bushings 3. Lubricate pivot bushings. Replace if
necessary.
DISC BRAKE CHIRP 1. Excessive brake rotor runout. 1. Follow brake rotor diagnosis and testing.
Correct as necessary.
2. Lack of lubricant on brake caliper
slides.2. Lubricate brake caliper slides.
3. Caliper/shoes not fully seated. 3. Reseat caliper/shoes.
DISC BRAKE RATTLE OR
CLUNK1. Broken or missing anti-rattle
spring clips on shoes.1. Replace brake shoes.
2. Caliper guide pins/bolts loose. 2. Tighten guide pins/bolts.
DISC BRAKE SQUEAK AT
LOW SPEED (WHILE
APPLYING LIGHT BRAKE
PEDAL EFFORT)1. Brake shoe linings. 1. Replace brake shoes.
DRUM BRAKE CHIRP 1. Lack of lubricant on brake shoe
support plate where shoes ride.1. Lubricate shoe contact areas on brake
shoe support plates.
DRUM BRAKE CLUNK 1. Drum(s) have threaded machined
braking surface.1. Replace brake drums as necessary.
DRUM BRAKE HOWL OR
MOAN1. Lack of lubricant on brake shoe
support plate where shoes ride and
at the anchor.1. Lubricate shoe contact areas on brake
shoe support plates and at the anchor.
2. Rear brake shoes. 2. Replace rear brake shoes.
DRUM BRAKE SCRAPING
OR WHIRRING1. ABS wheel speed sensor or tone
wheel.1. Inspect, correct or replace faulty
component(s).
RSBRAKES - BASE5-5
BRAKES - BASE (Continued)
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(6) Check pedal travel. If pedal travel is excessive
or has not been improved, enough fluid has not
passed through the system to expel all the trapped
air. Be sure to monitor the fluid level in the pressure
bleeder, so it stays at a proper level so air will not
enter the brake system through the master cylinder.
(7) Perform a final adjustment of the rear brake
shoes (when applicable), then test drive vehicle to be
sure brakes are operating correctly and that pedal is
solid.
SPECIFICATIONS
BRAKE FASTENER TORQUE
DESCRIPTION N´mFt.
Lbs.In.
Lbs.
ABS ICU Mounting Bolts To
Bracket11 Ð 9 7
ABS ICU Mounting
Bracket-To-Cradle Bolts28 21 250
ABS CAB-To-HCU Mounting
Screws2Ð17
ABS Wheel Speed Sensor
Head Mounting Bolt - Front13 Ð 115
ABS Wheel Speed Sensor
Head Mounting Bolt - Rear10 Ð 90
Adjustable Pedal Position
Sensor Mounting Screws7.5 66 Ð
Adjustable Pedal Module
Mounting Screws2.0 15 Ð
DESCRIPTION N´mFt.
Lbs.In.
Lbs.
Brake Tube Nuts 17 Ð 145
Brake Hose Intermediate
Bracket Bolt12 Ð 105
Brake Hose-To-Caliper
Mounting Bolt47 35 Ð
Disc Brake Caliper Guide
Pin Bolts35 26 Ð
Disc Brake Caliper Bleeder
Screw15 Ð 125
Drum Brake Wheel Cylinder
Mounting Bolts8Ð75
Drum Brake Wheel Cylinder
Mounting Bleeder screw10 Ð 80
Drum Brake Support Plate
Mounting Bolts130 95 Ð
Junction Block (Non-ABS
Brakes) Mounting Bolts28 21 250
Master Cylinder Mounting
Nuts25 19 225
Power Brake Booster
Mounting Nuts28 21 250
Proportioning Valve
Mounting Bolts54 40 Ð
Proportioning Valve Axle
Bracket Mounting Bolt20 Ð 175
Parking Brake Lever (Pedal)
Mounting Bolts And Nut28 21 250
Wheel Mounting (Lug) Nuts 135 100 Ð
SPECIAL TOOLS
BASE BRAKE SYSTEM
Fig. 3 TOOL 6921 INSTALLED ON MASTER
CYLINDER
1 - SPECIAL TOOL 6921
2 - FLUID RESERVOIR
Tubes, Master Cylinder Bleeding 6920
RSBRAKES - BASE5-9
BRAKES - BASE (Continued)
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SUPPORT PLATE - DRUM
BRAKE
REMOVAL
(1) Using a brake pedal depressor, move and
secure brake pedal to a position past its first 1 inch
of travel. This will prevent brake fluid from draining
out of master cylinder when brake tube is remove
from wheel cylinder.
(2) Raise vehicle. (Refer to LUBRICATION &
MAINTENANCE/HOISTING - STANDARD PROCE-
DURE).
(3) Remove wheel and tire assembly.
(4) Disconnect brake tube from rear of wheel cylin-
der. Cap open ends
(5) Remove brake drum.
(6) Remove brake shoes from brake support plate.
(Refer to 5 - BRAKES/HYDRAULIC/MECHANICAL/
BRAKE PADS/SHOES - REMOVAL).
(7) Remove the 2 bolts attaching the wheel cylin-
der to the brake support plate.
(8) Remove the wheel cylinder from the brake sup-
port plate.
(9) Disconnect the park brake cable from the park
brake actuation lever.
(10) Using a suitable tool such as a 14 mm box
wrench (Fig. 103) or an aircraft type hose clamp,
compress the flared legs on park brake cable
retainer. Then pull the park brake cable out of brake
support plate.(11) Remove the rear hub and bearing. (Refer to 2
- SUSPENSION/REAR/HUB / BEARING -
REMOVAL)
(12) Remove the rear brake support plate from the
rear axle.
INSTALLATION
(1) Install the 4 hub and bearing to axle mounting
bolts into the mounting holes in the flange of the
rear axle.
(2) Install the rear brake support plate on the 4
mounting bolts installed in the flange of the rear axle
(Fig. 104).
(3) Install the rear hub and bearing (and connect
wheel speed sensor where applicable) stopping short
of installing the brake drum. (Refer to 2 - SUSPEN-
SION/REAR/HUB / BEARING - INSTALLATION)
(4) Install the rear park brake cable into its
mounting hole in the rear brake support plate.
(5) Install the park brake cable on the park brake
actuation lever.
(6) Apply sealant such as Mopar Gasket-In-A-Tube
or equivalent around the wheel cylinder opening in
the brake support plate.
(7) Install wheel cylinder onto brake support.
Install and tighten the wheel cylinder to brake sup-
port plate attaching bolts to 8 N´m (75 in. lbs.)
torque.
(8) Install brake tube into wheel cylinder. Tighten
tube nut to a torque of 17 N´m (145 in. lbs.) torque.
(9) Install the rear brake shoes on the brake sup-
port plate. (Refer to 5 - BRAKES/HYDRAULIC/ME-
CHANICAL/BRAKE PADS/SHOES -
INSTALLATION).
(10) Install brake drum.
Fig. 103 Removing Park Brake Cable From Brake
Support Plate
1 - PARK BRAKE CABLE
2 - CABLE RETAINER
3 - 14 mm BOX WRENCH
4 - BRAKE SUPPORT PLATE
Fig. 104 Brake Support Plate Mounted On Bearing
Attaching Bolts
1 - REAR BRAKE SUPPORT PLATE
2 - HUB/BEARING MOUNTING BOLTS
5 - 64 BRAKES - BASERS
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(16) AWD only - Remove ABS wheel speed sensor
head from hub/bearing (Fig. 134).
(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. 135).
(b) Push up on metal retaining clip (Fig. 135)
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.
(18) Remove the hub/bearing-to-axle mounting
bolts (Fig. 136).
(19) Remove the hub/bearing (Fig. 137).
Fig. 134 Speed Sensor Attaching Bolt (AWD)
1 - ADAPTER
2 - TONE WHEEL
3 - WHEEL SPEED SENSOR
4 - AXLE
5 - BOLT
6 - DRIVESHAFT
Fig. 135 Sensor Connection At Hub And Bearing
1 - SECONDARY SENSOR RETAINING CLIP
2 - METAL SENSOR RETAINING CLIP
3 - HUB AND BEARING
Fig. 136 Hub/Bearing Mounting Bolts (AWD Shown)
1 - DRIVESHAFT
2 - MOUNTING BOLTS
3 - AXLE
4 - MOUNTING BOLTS
5 - ADAPTER
5 - 78 BRAKES - BASERS
SHOES - PARKING BRAKE (Continued)
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(11) Install the hub/bearing on the stub shaft of
outer C/V joint (AWD only) and into the end of the
axle. (Fig. 137).
(12) In a progressive crisscross pattern, tighten
the 4 hub/bearing mounting bolts until the hub/bear-
ing is squarely seated against the axle. Then tighten
the hub/bearing mounting bolts to a torque of 129
N´m (95 ft. lbs.).
(13) AWD only - Install the wheel speed sensor on
the hub/bearing and adapter. Install the wheel speed
sensor attaching bolt (Fig. 134). 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. 132).
(17) Attach park brake cable to adapter using
mounting bolt.
(18) Remove the locking pliers (Fig. 128) 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. 130).
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. 129).
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. 127) 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.
126) on the stub shaft of the outer C/V joint.
(27) AWD only - Install the nut retainer and cotter
pin (Fig. 125) 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.
Fig. 146 Adapter Installed On Mounting Bolts (AWD
Shown)
1 - DRIVESHAFT OUTER C/V JOINT
2 - MOUNTING BOLTS
3 - ADAPTER
4 - PARK BRAKE SHOES
5 - MOUNTING BOLTS
5 - 82 BRAKES - BASERS
SHOES - PARKING BRAKE (Continued)
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BRAKES - ABS
TABLE OF CONTENTS
page page
BRAKES - ABS
DESCRIPTION
DESCRIPTION - ANTILOCK BRAKE
SYSTEM............................85
DESCRIPTION - ANTILOCK BRAKE
SYSTEM (EXPORT)....................85
DESCRIPTION - ELECTRONIC VARIABLE
BRAKE PROPORTIONING...............86
DESCRIPTION - TRACTION CONTROL
SYSTEM............................86
OPERATION
OPERATION - ANTILOCK BRAKE SYSTEM . . 86
OPERATION - ELECTRONIC VARIABLE
BRAKE PROPORTIONING...............87
OPERATION - TRACTION CONTROL
SYSTEM............................87
CAUTION
CAUTIONS..........................88
STANDARD PROCEDURE - ANTILOCK BRAKE
SYSTEM BLEEDING...................88
SPECIFICATIONS
ABS FASTENER TORQUE...............89
TONE WHEEL RUNOUT................89
WHEEL SPEED SENSOR AIR GAP........89
FRONT WHEEL SPEED SENSOR
REMOVAL.............................89
INSTALLATION.........................89
REAR WHEEL SPEED SENSOR - AWD
REMOVAL.............................90INSTALLATION.........................90
REAR WHEEL SPEED SENSOR - FWD
REMOVAL.............................91
INSTALLATION.........................91
TONE WHEEL
INSPECTION - TONE WHEEL..............92
TRACTION CONTROL SWITCH
DIAGNOSIS AND TESTING - TRACTION
CONTROL SWITCH....................92
HYDRAULIC/MECHANICAL
OPERATION - HYDRAULIC CIRCUITS AND
VALVES .............................93
HCU (HYDRAULIC CONTROL UNIT)
DESCRIPTION.........................99
OPERATION...........................99
ICU (INTEGRATED CONTROL UNIT)
DESCRIPTION........................100
OPERATION..........................100
REMOVAL
REMOVAL - LHD.....................100
REMOVAL - RHD.....................101
DISASSEMBLY - ICU...................103
ASSEMBLY - ICU......................103
INSTALLATION
INSTALLATION - LHD.................104
INSTALLATION - RHD.................105
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.
RSBRAKES - ABS5-85
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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-
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).
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 sys-
tem enters the ABS mode. During ABS braking,
hydraulic pressure in the four wheel circuits is mod-ulated to prevent any wheel from locking. Each
wheel circuit is designed with a set of electric sole-
noids to allow modulation, although for vehicle sta-
bility, 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 nor-
mal.
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
5 - 86 BRAKES - ABSRS
BRAKES - ABS (Continued)
ProCarManuals.com

black tire marks since the wheel never reaches a
fully locked condition. However, tire marks may 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.
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 thepressure 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 the
master 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
RSBRAKES - ABS5-87
BRAKES - ABS (Continued)
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ªthermo-protection mode,º the traction control func-
tion lamp illuminates TRAC OFF; note that no trou-
ble code is registered.
CAUTION
CAUTIONS
The ABS uses an electronic control module, the
CAB. This module is designed to withstand normal
current draws associated with vehicle operation.
Care must be taken to avoid overloading the CAB
circuits.
CAUTION: In testing for open or short circuits, do
not ground or apply voltage to any of the circuits
unless instructed to do so for a diagnostic proce-
dure.
CAUTION: These circuits should only be tested
using a high impedance multi-meter or the DRBIIIT
scan tool as described in this section. Power
should never be removed or applied to any control
module with the ignition in the ON position. Before
removing or connecting battery cables, fuses, or
connectors, always turn the ignition to the OFF
position.
CAUTION: The CAB 24-way connector should never
be connected or disconnected with the ignition
switch in the ON position.
CAUTION: This vehicle utilizes active wheel speed
sensors. Do not apply voltage to wheel speed sen-
sors at any time.
CAUTION: Use only factory wiring harnesses. Do
not cut or splice wiring to the brake circuits. The
addition of aftermarket electrical equipment (car
phone, radar detector, citizen band radio, trailer
lighting, trailer brakes, etc.) on a vehicle equipped
with antilock brakes may affect the function of the
antilock brake system.
CAUTION: When performing any service procedure
on a vehicle equipped with ABS, do not apply a
12-volt power source to the ground circuit of the
pump motor in the HCU. Doing this will damage the
pump motor and will require replacement of the
entire HCU.CAUTION: An attempt to remove or disconnect cer-
tain system components may result in improper
system operation. Only those components with
approved removal and installation procedures in
this manual should be serviced.
CAUTION: If welding work is to be performed on the
vehicle, using an electric arc welder, the CAB con-
nector should be disconnected during the welding
operation.
CAUTION: Many components of the ABS System
are not serviceable and must be replaced as an
assembly. Do not disassemble any component
which is not designed to be serviced.
CAUTION: Only the recommended jacking or hoist-
ing positions for this vehicle are to be used when-
ever it is necessary to lift a vehicle. Failure to raise
a vehicle from the recommended locations could
result in lifting a vehicle by the hydraulic control
unit mounting bracket. Lifting a vehicle by the
hydraulic control unit mounting bracket will result
in damage to the mounting bracket and the hydrau-
lic control unit.
CAUTION: Brake fluid will damage painted surfaces.
If brake fluid is spilled on any painted surface,
wash off with water immediately.
STANDARD PROCEDURE - ANTILOCK BRAKE
SYSTEM BLEEDING
The base brake's hydraulic system must be bled
anytime air enters the hydraulic system. The ABS
though, particularly the ICU (HCU), should only be
bled when the HCU is replaced or removed from the
vehicle. The ABS must always be bled anytime it is
suspected that the HCU has ingested air. Under
most circumstances that require the bleeding of the
brakes hydraulic system, only the base brake
hydraulic system needs to be bled.
It is important to note that excessive air in the
brake system will cause a soft or spongy feeling
brake pedal.
During the brake bleeding procedure, be sure the
brake fluid level remains close to the FULL level in
the master cylinder fluid reservoir. Check the fluid
level periodically during the bleeding procedure and
add DOT 3 brake fluid as required.
The ABS must be bled as two independent braking
systems. The non-ABS portion of the brake system
with ABS is to be bled the same as any non-ABS sys-
tem.
5 - 88 BRAKES - ABSRS
BRAKES - ABS (Continued)
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