brakes DODGE NEON 2000 Service Manual PDF

(4) Install piston into caliper bore pushing it past
the piston seal until it bottoms in the caliper bore
(Fig. 122).
(5) Position the dust boot into the counterbore of
the caliper assembly piston bore.
(6) Using a hammer and Installer, Special Tool
C-4689, and Handle, Special Tool C-4171, drive the
boot into the counterbore of the caliper (Fig. 123).
(7) Install the brake shoes.
(8) Reinstall the caliper on the vehicle and bleed
the brakes as necessary. Follow the installation pro-
cedure found in DISC BRAKE CALIPER in the
REMOVAL AND INSTALLATION section in this sec-
tion of this service manual group.
CLEANING AND INSPECTION
BRAKE TUBES AND HOSES
Flexible rubber hose is used at both front and rear
brakes. Inspection of brake hoses should be per-
formed whenever the brake system is serviced and
every 7,500 miles or 12 months, whichever comes
first (every engine oil change). Inspect hydraulic
brake hoses for severe surface cracking, scuffing,
worn spots or physical damage. If the fabric casing of
the rubber hose becomes exposed due to cracks or
abrasions in the rubber hose cover, the hose should
be replaced immediately. Eventual deterioration of
the hose can take place with possible burst failure.
Faulty installation can cause twisting, resulting in
wheel, tire, or chassis interference.The steel brake tubing should be inspected period-
ically for evidence of corrosion, physical damage or
contact with moving or hot components of the vehi-
cle.
DISC BRAKES (FRONT)
BRAKE SHOES
Clean the front brake shoes and calipers with a
water-dampened cloth or with a brake cleaner. Do
not use a petroleum based product.
If a visual inspection does not adequately deter-
mine the condition of the lining, a physical check will
be necessary.
Remove the front disc brake shoes. Refer to DISC
BRAKE SHOES in the REMOVAL AND INSTALLA-
TION section in this section of this service manual
group.
The combined brake shoe and lining material
thickness should be measured at the thinnest part of
the assembly.
When a set of brake shoes are worn to a total
thickness of approximately 7.95 mm (5/16 inch) or
less, they should be replaced.
Replace both brake shoe assemblies (inboard and
outboard). It is necessary that both front wheel sets
be replaced whenever brake shoe assemblies on
either side are replaced.
Fig. 122 Installing Piston Into Caliper Bore
1 ± BOOT
2 ± PISTON
3 ± CALIPER
Fig. 123 Installing Dust Boot In Caliper Counterbore
1 ± HAMMER
2 ± SPECIAL TOOL C-4171
3 ± SPECIAL TOOL C-4689
4 ± CALIPER
PLBRAKES 5 - 59
DISASSEMBLY AND ASSEMBLY (Continued)

If the brake shoe assemblies do not require
replacement, reinstall the assemblies making sure
each brake shoe is returned to the original position.
Refer to DISC BRAKE SHOES in the REMOVAL
AND INSTALLATION section in this section of this
service manual group.
CALIPER INSPECTION
Check for brake fluid leaks in and around the boot
area. Check for any ruptures, brittleness or damage
to the piston dust boot. If the boot is damaged, or a
fluid leak is visible, disassemble the caliper assembly
and install a new seal and boot, and a piston if it is
scored. Refer to DISC BRAKE CALIPER in the DIS-
ASSEMBLY AND ASSEMBLY section in this section
of this service manual group.
Check the guide pin dust boots to determine if they
are in good condition. Replace if they are damaged,
dry, or found to be brittle. Refer to DISC BRAKE
CALIPER in the DISASSEMBLY AND ASSEMBLY
section in this section of this service manual group.
DISC BRAKES (REAR)
BRAKE SHOES
Clean the rear brake shoes and calipers with a
water-dampened cloth or with a brake cleaner. Do
not use a petroleum based product.
If a visual inspection does not adequately deter-
mine the condition of the lining, a physical check will
be necessary.
Remove the rear disc brake shoes. Refer to DISC
BRAKE SHOES in the REMOVAL AND INSTALLA-
TION section in this section of this service manual
group.
The combined brake shoe and lining material
thickness should be measured at the thinnest part of
the assembly.
When a set of brake shoes are worn to a total
thickness of approximately 7.0 mm (9/32 inch) or
less, they should be replaced.
Replace both brake shoe assemblies (inboard and
outboard). It is necessary that both front wheel sets
be replaced whenever brake shoe assemblies on
either side are replaced.
If the brake shoe assemblies do not require
replacement, reinstall the assemblies making sure
each brake shoe is returned to the original position.
Refer to DISC BRAKE SHOES in the REMOVAL
AND INSTALLATION section in this section of this
service manual group.
CALIPER INSPECTION
Check for brake fluid leaks in and around the boot
area. Check for any ruptures, brittleness or damage
to the piston dust boot. If the boot is damaged, or afluid leak is visible, disassemble the caliper assembly
and install a new seal and boot, and a piston if it is
scored. Refer to DISC BRAKE CALIPER in the DIS-
ASSEMBLY AND ASSEMBLY section in this section
of this service manual group.
Check the guide pin dust boots to determine if they
are in good condition. Replace if they are damaged,
dry, or found to be brittle. Refer to DISC BRAKE
CALIPER in the DISASSEMBLY AND ASSEMBLY
section in this section of this service manual group.
DRUM BRAKES (REAR)
BRAKE SHOES
Clean the rear brake shoes and springs with a
water-dampened cloth or with a brake cleaner. Do
not use a petroleum based product.
Rear brake shoe lining should show contact across
the entire width of the lining and also from the heel
to the toe of the lining. Replace the shoes if noted
otherwise.
Brake shoes with lack of contact at the toe or heel
of the brake shoe lining may be improperly ground.
Clean and inspect the brake support plate and
shoe adjuster screw. Apply a thin coat of Mopart
Multi-Purpose Lubricant or equivalent to the threads
of the self-adjuster (Fig. 124). Replace the adjuster
screw if it is corroded.
NOTE: Adjuster screws are different side-to-side.
Left side adjuster screws have left-hand threads
and right side adjuster screws have right-handed
threads.
If the old brake shoe return or hold down springs
have overheated or are damaged, replace them. Over-
heating indications are paint discoloration or dis-
torted end coils.
Fig. 124 Adjuster Screw And Lever (Typical)
1 ± OUTBOARD FORWARD
2 ± SELF ADJUSTER
3 ± OUTBOARD REAR
4 ± SELF ADJUSTER LEVER
5 - 60 BRAKESPL
CLEANING AND INSPECTION (Continued)

WHEEL CYLINDER
With the brake drums removed, inspect the wheel
cylinder boots for evidence of a brake fluid leak.
Visually check the boots for cuts, tears, or heat
cracks. If any of these conditions exist, the wheel cyl-
inders should be completely cleaned, inspected and
new parts installed.
If a wheel cylinder is leaking and the brake lining
material is saturated with brake fluid, the brake
shoes must be replaced.
ADJUSTMENTS
BRAKE LAMP SWITCH
(1) Depress and hold the brake pedal while rotat-
ing the brake lamp switch (Fig. 125) in a counter-
clockwise direction approximately 30 degrees.
(2) Pull the switch rearward and remove it from
its mounting bracket.
(3) If necessary, disconnect the wiring harness con-
nector from the switch.
(4) Hold the brake lamp switch firmly in one hand.
Using the other hand, pull outward on the plunger of
the switch until it has ratcheted out to its fully
extended position.
(5) If disconnected, connect the wiring harness
connector to the stop lamp switch.(6) Mount the brake lamp switch into the bracket
using the following procedure:
²Depress the brake pedal as far down as possible.
²Install the switch in its bracket by aligning the
index tab on the switch with the slot in the mounting
bracket.
²When the switch is fully seated in its bracket,
rotate the switch clockwise approximately 30É to lock
the switch into place.
CAUTION: Do not use excessive force when pulling
back on the brake pedal to adjust the brake lamp
switch. If too much force is used, the switch or
striker can be damaged.
(7) Gently pull back on the brake pedal until the
pedal stops moving. This will ratchet the switch
plunger backward to the correct adjustment position.
(8) Check the stop lamps to verify that they are
operating properly and not staying on when the
pedal is in the released position.
DRUM BRAKE SHOES
(1) Verify the parking brake lever is in the fully
released position.
(2) Raise the vehicle. Refer to HOISTING in the
LUBRICATION AND MAINTENANCE group fro the
proper lifting procedure.
(3) Remove the rear brake adjusting hole rubber
plug from the rear brake shoe support plate (Fig.
126).
Fig. 125 Brake Lamp Switch
1 ± SWITCH
2 ± CLIP
3 ± BRAKE PEDAL
4 ± CONNECTOR
Fig. 126 Rear Brake Adjusting Hole Plug
1 ± REAR BRAKE SUPPORT PLATE
2 ± REAR STRUT
3 ± BRAKE ADJUSTING HOLE PLUG
PLBRAKES 5 - 61
CLEANING AND INSPECTION (Continued)

(4) Insert a brake adjustment tool, or a screw-
driver, through the adjusting hole in support plate
and against the star wheel of the adjuster screw.
Move the handle of tool downward to adjust the
brake drag. Rotate the tire and wheel assembly while
adjusting the adjuster screw. Continue to adjust the
shoes until a slight drag is noticed when the tire and
wheel assembly is rotated.
NOTE: In the event the brake shoes are over-ad-
justed, the adjuster can be backed off using the fol-
lowing step. If not, proceed to step 6.
(5) If the shoes are in the over-adjusted position,
insert a thin screwdriver into brake adjusting hole
and push back the adjusting lever out of engagement
with star wheel (Fig. 127). Take care not to bend the
adjusting lever. While holding the adjusting lever out
of engagement with star wheel, back off the star
wheel until the tire and wheel assembly is free to
turn without dragging. Repeat the adjustment proce-
dure.
(6) Install adjusting hole rubber plug (Fig. 126).
(7) Repeat the above adjustment procedure to the
other side brakes.
(8) Apply and release the park brake lever one
time after the adjustment process is completed so the
parking brakes can readjust themselves to the new
brake shoe adjustment.
PARKING BRAKE SHOES (REAR DISC BRAKES)
NOTE: The parking brake shoes used in the drum-
in-hat park brake system do not automatically
adjust to compensate for brake shoe lining wear.Therefore, it is necessary to manually adjust the
parking brake shoes.
(1) Verify the parking brake lever is in the
released position.
(2) Raise the vehicle. Refer to HOISTING in the
LUBRICATION AND MAINTENANCE group for the
proper lifting procedure.
(3) Remove the rubber plug from the adjusting
hole in the disc brake caliper adapter.
(4) Adjust the parking brakes. Use the first bullet
point for the adjustment of the left side parking
brake shoes. Use the second bullet point for the
adjustment of the right side parking brake shoes.
²Insert a medium size screwdriver through
adjustment hole in the left backing plate. Position
the screwdriver against the star wheel on the park-
ing brake shoe adjuster. Using the screwdriver,
rotate the star wheel downward until a slight drag is
noticed when turning the rear tire and wheel assem-
bly. Then, using the screwdriver, slowly rotate the
star wheel upward, backing off the adjuster, just
enough to allow the rear tire and wheel assembly to
rotate without the parking brake shoes dragging. Do
not back off the adjuster star wheel more than two
clicks past the point of no drag. The parking brake
shoe-to-drum clearance is now properly set.
²Insert a medium size screwdriver through
adjustment hole in the right backing plate. Position
the screwdriver against the star wheel on the park-
ing brake shoe adjuster. Using the screwdriver,
rotate the star wheel upward until a slight drag is
noticed when turning the rear tire and wheel assem-
bly. Then, using the screwdriver, slowly rotate the
star wheel downward, backing off the adjuster, just
enough to allow the rear tire and wheel assembly to
rotate without the parking brake shoes dragging. Do
not back off the adjuster star wheel more that two
clicks past the point of no drag. The parking brake
shoe-to-drum clearance is now properly set.
(5) Install the rubber plug in the adjusting holes of
the disc brake caliper adapter.
(6) Lower the vehicle until the rear tires are just
clearing the floor.
(7) Reach inside the vehicle and fully apply and
release the park brakes two times after adjusting the
parking brake shoes.
(8) With the parking brake lever in the fully
applied position, attempt to hand rotate each rear
tire and wheel assembly to ensure that the parking
brake shoes are working.
(9) With the parking brake lever in the released
position, hand rotate each rear tire and wheel assem-
bly to ensure that the parking brake shoes are not
dragging.
Fig. 127 Backing Off Brake Adjuster Screw
1 ± MEDIUM SCREWDRIVER
2 ± BRAKE ADJUSTING HOLE
3 ± THIN SCREWDRIVER OR WELDING ROD
5 - 62 BRAKESPL
ADJUSTMENTS (Continued)

SPECIFICATIONS
BRAKE FLUID
The brake fluid used in this vehicle must conform
to DOT 3 specifications and SAE J1703 standards.
No other type of brake fluid is recommended or
approved for usage in the vehicle brake system. Use
only Mopar brake fluid or an equivalent from a
tightly sealed container.
CAUTION: Never use reclaimed brake fluid or fluid
from an container which has been left open. An
open container will absorb moisture from the air
and contaminate the fluid.
CAUTION: Never use any type of a petroleum-
based fluid in the brake hydraulic system. Use of
such type fluids will result in seal damage of the
vehicle brake hydraulic system causing a failure of
the vehicle brake system. Petroleum based fluids
would be items such as engine oil, transmission
fluid, power steering fluid, etc.
BRAKE ACTUATION SYSTEM
ACTUATION:
Vacuum Operated Power Brakes.....Standard
Hydraulic System.......Dual-Diagonally Split
BRAKE PEDAL:
Pedal Ratio..........................3.41
POWER BRAKE BOOSTER:
Make/Type..................Bosch/Vacuum
Mounting Studs.................. M8x1.25
Diaphragm Size/Type........ 205mmTandem
MASTER CYLINDER ASSEMBLY:
Type ........................Dual Tandem
Body Material...........Anodized Aluminum
Reservoir Material.............Polypropelene
MASTER CYLINDER BORE STROKE AND
SPLIT:
NonABS ..............22.23 mm x 34.0 mm
(0.875 in. x 1.34 in.)
ABS . . 23.82 mm x 34.0 mm (0.937 in. x 1.34 in.)
Displacement Split.................. 50/50MASTER CYLINDER FLUID OUTLET PORTS:
Tube Fitting Type...... SAE45ÉInverted Flare
W/ABS - Primary Tube Nut
Thread........................7/16 in.±24
W/ABS - Secondary Tube Nut
Thread........................ 3/8in.±24
W/O ABS - All Tube Nut Threads....7/16 in.±24
ABS HYDRAULIC CONTROL UNIT:
Hydraulic Tube Fitting
Type................ SAE45ÉInverted Flare
All Tube Nut Threads............7/16 in.±24
PROPORTIONING VALVE:
Material.......................Aluminum
Function.....Hydraulic Pressure Proportioning
BRAKE FASTENER TORQUE SPECIFICATIONS
DESCRIPTION TORQUE
BRAKE TUBES:
Tube Nuts............... 17N´m(145 in. lbs.)
MASTER CYLINDER:
Mounting Nuts.......... 28N´m(250 in. lbs.)
POWER BRAKE BOOSTER:
Mounting Nuts.......... 34N´m(300 in. lbs.)
DISC BRAKE CALIPER:
Caliper Banjo Bolt......... 48N´m(35ft.lbs.)
Guide Pin Bolts.......... 22N´m(192 in. lbs.)
Bleeder Screw........... 15N´m(125 in. lbs.)
WHEEL CYLINDER (REAR):
Mounting Bolts.......... 13N´m(115in.lbs.)
Bleeder Screw............ 10N´m(80in.lbs.)
DRUM BRAKE SHOE SUPPORT PLATE
(REAR):
Mounting Bolts........... 75N´m(55ft.lbs.)
DISC BRAKE ADAPTER (REAR):
Mounting Bolts........... 75N´m(55ft.lbs.)
HUB AND BEARING (REAR):
Retaining Nut.......... 217N´m(160 ft. lbs.)
PARKING BRAKE:
Lever Mounting Nuts..... 28N´m(250 in. lbs.)
TIRE AND WHEEL:
Wheel Mounting Nut...........109±150 N´m
(80±110 ft. lbs.)
INTEGRATED CONTROL UNIT:
Mounting Bolts........... 11N´m(97in.lbs.)
CAB Mounting bolts........ 2N´m(17in.lbs.)
Bracket-to-Frame Rail Bolts.......... 23N´m
(200 in. lbs.)
WHEEL SPEED SENSOR:
Head Mounting bolt...... 12N´m(105 in. lbs.)
PLBRAKES 5 - 63

SPECIAL TOOLS
BASE BRAKE SYSTEM
Adapters, Brake Pressure 6805
Adapter, Brake Pressure 8644
Gauge Set C-4007-A
Handle, Universal C-4171
Installer, Dust Boot C-4689
Dial Indicator C-3339
Tubes, Master Cylinder Bleed 8358
5 - 64 BRAKESPL

ANTILOCK BRAKE SYSTEM
TABLE OF CONTENTS
page page
DESCRIPTION AND OPERATION
ANTILOCK BRAKE SYSTEM OPERATION......65
ANTILOCK BRAKE SYSTEM COMPONENTS....66
ELECTRONIC BRAKE DISTRIBUTION.........69
TRACTION CONTROL SYSTEM..............70
HYDRAULIC CIRCUITS AND VALVE
OPERATION...........................71
DIAGNOSIS AND TESTING
SERVICE WARNINGS AND CAUTIONS........74
ABS GENERAL DIAGNOSTICS INFORMATION . . 74
ABS WIRING DIAGRAM INFORMATION........74
ABS VEHICLE TEST DRIVE.................74
ABS ELECTRONIC DIAGNOSIS..............75
TONE WHEEL...........................76
BRAKE FLUID CONTAMINATION.............76
SERVICE PROCEDURES
BRAKE FLUID LEVEL CHECKING............77ANTILOCK BRAKE SYSTEM BLEEDING.......77
MASTER CYLINDER BLEEDING.............77
REMOVAL AND INSTALLATION
SERVICE WARNINGS AND CAUTIONS........78
MASTER CYLINDER......................78
INTEGRATED CONTROL UNIT...............79
WHEEL SPEED SENSOR (FRONT)...........81
WHEEL SPEED SENSOR (REAR)............83
DISASSEMBLY AND ASSEMBLY
INTEGRATED CONTROL UNIT...............84
SPECIFICATIONS
TONE WHEEL RUNOUT....................85
WHEEL SPEED SENSOR-TO-TONE WHEEL
CLEARANCE...........................85
BRAKE FASTENER TORQUE
SPECIFICATIONS.......................85
DESCRIPTION AND OPERATION
ANTILOCK BRAKE SYSTEM OPERATION
This section covers the physical and operational
descriptions, and the on-car service procedures for
the Mark 20e Antilock Brake System (ABS) with
traction control. It is the only antilock brake system
available on this vehicle.
The purpose of the antilock brake system is to pre-
vent wheel lockup under braking conditions on virtu-
ally 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.
The traction control system reduces wheel slip and
maintains traction at the driving speeds below 56
kph (35 mph) when road conditions call for traction
assistance. Refer to TRACTION CONTROL SYSTEM
in this section for more information.
Vehicles equipped with ABS use electronic brake
distribution (EBD) to balance front-to-rear braking
when the brakes are applied in the partial braking
range. Refer to ELECTRONIC BRAKE DISTRIBU-
TION in this section for more information.
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 four control channels.
During antilock operation of the vehicle's brake sys-
tem, the wheels are controlled independently and are
on separate control channels.
The system can build, hold 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).
PLBRAKES 5 - 65

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.
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.
ANTILOCK BRAKE SYSTEM COMPONENTS
The following is a detailed description of the
antilock brake system components. For information
on servicing base brake system components used in
conjunction with these components, see the BASE
BRAKE SYSTEM found at the beginning of this ser-
vice manual group.
MASTER CYLINDER
A vehicle equipped with ABS uses a different mas-
ter cylinder than a vehicle that is not equipped with
ABS. Vehicles equipped with ABS use a center port
master cylinder with only two outlet ports (Fig. 1).
The brake tubes from the primary and secondary
outlet ports on the master cylinder go directly to the
integrated control unit (ICU).
The master cylinder mounts to the power brake
booster in the same manner a non-ABS master cylin-
der does.
INTEGRATED CONTROL UNIT (ICU)
The hydraulic control unit (HCU) and the control-
ler antilock brake (CAB) used with this antilock
brake system are combined (integrated) into one
unit, which is called the integrated control unit (ICU)
(Fig. 2). The ICU is located on the driver's side of the
vehicle, and is mounted to the left front frame rail
below the master cylinder (Fig. 1).
5 - 66 BRAKESPL
DESCRIPTION AND OPERATION (Continued)

The ABS with traction control ICU consists of the
following components: the CAB, eight (build/decay)
solenoid valves (four inlet valves and four outlet
valves), two hydraulic shuttle valves, two traction
control valves, valve block, fluid accumulators, a
pump, and an electric pump/motor.
The replaceable components of the ICU are the
HCU and the CAB. No attempt should be made to
service any components found inside of the HCU or
CAB.
CONTROLLER ANTILOCK BRAKE (CAB)
The controller antilock brake (CAB) is a micropro-
cessor-based device which monitors the ABS system
during normal braking and controls it when the vehi-
cle is in an ABS stop. The CAB is mounted to the
bottom of the HCU (Fig. 2). The CAB uses a 25-way
electrical connector on the vehicle wiring harness.
The power source for the CAB is through the ignition
switch in the RUN or ON position. The CAB is on
the PCI bus.
The primary functions of the (CAB) are to:
(1) monitor the antilock brake system for proper
operation.
(2) detect wheel locking or wheel slipping tenden-
cies by monitoring the speed of all four wheels of the
vehicle.
(3) control fluid modulation to the wheel brakes
while the system is in an ABS mode or the traction
control system is activated.
(4) store diagnostic information.
(5) provide communication to the DRB scan tool
while in diagnostic mode.
The CAB constantly monitors the antilock brake
system for proper operation. If the CAB detects a
fault, it will send a message to the mechanical instu-
ment cluster (MIC) instructing it to turn on the
amber ABS warning lamp and disable the antilock
braking system. The normal base braking system will
remain operational.
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 that 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 CAB contains a self-diagnostic program that
monitors the antilock brake system for system faults.
When a fault is detected, the amber ABS warning
lamp is turned on and the fault diagnostic trouble
code (DTC) is then stored in a diagnostic program
memory. These DTC's will remain in the CAB mem-
ory even after the ignition has been turned off. The
DTC's can be read and cleared from the CAB mem-
ory by a technician using the DRB scan tool. If not
cleared with a DRB scan tool, the fault occurrence
and DTC will be automatically cleared from the CAB
memory after the identical fault has not been seen
during the next 3,500 miles of vehicle operation.
Fig. 1 Master Cylinder And ICU
1 ± PRIMARY BRAKE TUBE
2 ± MASTER CYLINDER
3 ± SECONDARY BRAKE TUBE
4 ± ABS ICU
Fig. 2 Integrated Control Unit (ICU)
1 ± HCU
2 ± PUMP/MOTOR
3 ± CAB
PLBRAKES 5 - 67
DESCRIPTION AND OPERATION (Continued)

CONTROLLER ANTILOCK BRAKE INPUTS
²wheel speed sensors (four)
²stop lamp switch
²ignition switch
²system relay voltage
²ground
²traction control lamp
²diagnostic communication (PCI)
CONTROLLER ANTILOCK BRAKE OUTPUTS
²amber ABS warning lamp actuation (through
MIC)
²red BRAKE warning lamp actuation (through
MIC)
²traction control lamp actuation (through MIC)
²diagnostic communication. (PCI)
HYDRAULIC CONTROL UNIT (HCU)
The hydraulic control unit (HCU) is mounted to
the CAB as part of the ICU (Fig. 2). The HCU con-
trols the flow of brake fluid to the brakes using a
series of valves and accumulators. A pump/motor is
mounted on the HCU to supply build pressure to the
brakes during an ABS stop.
VALVES AND SOLENOIDS
The valve block contains four inlet valves and four
outlet solenoid valves. The inlet valves are spring-
loaded in the open position and the outlet valves are
spring-loaded in the closed position during normal
braking. The fluid is allowed to flow from the master
cylinder to the wheel brakes.
During an ABS stop, these valves cycle to maintain
the proper slip ratio for each wheel. The inlet valve
closes preventing further pressure increase and the
outlet valve opens to provide a path from the wheel
brake to the HCU accumulators and pump/motor.
This releases (decays) pressure from the wheel brake,
thus releasing the wheel from excessive slippage.
Once the wheel is no longer slipping, the outlet valve
is closed and the inlet valve is opened to reapply
(build) pressure.
There are four other valves in the HCU. These four
remaining valves are used for traction control. Two
traction control (TC) valves, mounted in the HCU
valve block, are normally in the open position and
close only when the traction control is applied. There
are also two shuttle valves which control pressure
return to the master cylinder under ABS and traction
control conditions.
These TC valves are used to isolate the rear (non-
driving) wheels of the vehicle from the hydraulic
pressure that the HCU pump/motor is sending to the
front (driving) wheels when traction control is being
applied. The rear brakes need to be isolated from the
master cylinder when traction control is beingapplied so the rear wheels do not drag. For more
information on the TC and shuttle valves, see TRAC-
TION CONTROL SYSTEM in this section.
BRAKE FLUID ACCUMULATORS
There are two fluid accumulators in the HCU: one
for the primary hydraulic circuit, and one for the sec-
ondary hydraulic circuit. Each hydraulic circuit uses
a 3 cc accumulator.
The fluid accumulators temporarily store brake
fluid that is removed from the wheel brakes during
an ABS cycle. This stored fluid is used by the pump/
motor to provide build pressure for the brake hydrau-
lic system. When the antilock stop is complete, the
accumulators are drained by the pump/motor.
There are two noise dampening chambers in the
HCU on this vehicle equipped with traction control.
PUMP/MOTOR
There are two pump assemblies in the HCU: one
for the primary hydraulic circuit, and one for the sec-
ondary hydraulic circuit. Both pumps are driven by a
common electric motor (Fig. 2). This DC-type motor
is integral to the HCU and is controlled by the CAB.
The pump/motor provides the extra amount of
brake fluid needed during antilock braking. Brake
fluid is released to the accumulators when the outlet
valve is opened during an antilock stop. The pump
mechanism consists of two opposing pistons operated
by an eccentric camshaft. In operation, these pistons
are used to purge fluid from the accumulators back
into the master cylinder circuits. When the antilock
stop is complete, the pump/motor drains the accumu-
lators.
The pump motor is also used to build pressure
when the system goes into traction control mode. For
more information, refer to TRACTION CONTROL
SYSTEM in this section.
The CAB may turn on the pump/motor when an
antilock stop is detected. The pump/motor continues
to run during the antilock stop and is turned off after
the stop is complete. Under some conditions, the
pump/motor runs to drain the accumulators during
the next drive-off.
The pump/motor is not a serviceable item; if it
requires replacement, the HCU must be replaced.
ABS FUSES
The ABS fuse and the ABS pump/motor fuse are
located in the power distribution center (PDC). Refer
to the sticker on the inside of the PDC cover for the
location of these fuses. The PDC is located on the
driver's side of the engine compartment between the
back of the battery and the brake master cylinder.
The CAB fuse can be found in the fuse junction
block under the instrument panel.
5 - 68 BRAKESPL
DESCRIPTION AND OPERATION (Continued)