battery CHEVROLET DYNASTY 1993 User Guide

(1) Remove dryer-to-compressor retaining screw
(Fig. 13). (2) Rotate dryer assembly 90É to release retaining
tangs from exhaust solenoid housing and withdraw
unit.
INSTALLATION
Inspect O-Ring for damage and location on dryer
assembly. (1) Insert and index air dryer locking tangs into
exhaust solenoid outlet. (2) Rotate air dryer assembly to lock position and
install air dryer-to-compressor retaining screw (Fig.
13).
SOLENOIDS (STRUTS AND AIR SPRINGS)
Front struts and rear springs are equipped with so-
lenoids that control air pressure and volume within
the assemblies. The solenoids are electrically oper-
ated to allow air input, contain air, or release air
pressure, depending on control module commands.
REMOVAL
WARNING: DO NOT ATTEMPT TO REMOVE OR IN-
STALL SOLENOIDS WHILE AIR SUSPENSION
(FRONT STRUTS AND REAR AIR SPRINGS) ARE
SUPPORTING VEHICLE.
Disconnect negative battery cable. Raise vehicle
and remove wheel and tire assembly then remove so-
lenoid(s) as follows: (1) Separate electrical connection to solenoid.
(2) Disconnect air line, see Air Lines and Fittings.
Solenoids have molded square tangs to fit into
stepped notches of the air spring housing. The
notches provide an air relief position and a retaining
position. The retaining position is locked with a re-
taining clip. (3) Remove retaining clip (Fig. 14). (4) Rotate solenoid to first step in housing and al-
low air pressure to vent (Fig. 15).
(5) Rotate solenoid to release slot and remove (Fig.
16).
Fig. 13 Air Dryer Remove/Install
Fig. 14 Remove Retaining Clips
Fig. 15 Release Air Pressure
Fig. 16 Remove Solenoid (Inspect O Ring)
2 - 86 SUSPENSION AND DRIVESHAFTS Ä

INSTALL
(1) Inspect O-Ring condition and position on sole-
noid stem. (O-Ring can become dislodged during re-
moval (Fig. 16). (2) Install solenoid with tangs to top ledge of hous-
ing and install retaining clip. (3) Reconnect air line and electrical connection.
STRUT (AIR SUSPENSION) DAMPERASSEMBLY
Service procedures for removal and installation for
(air or steel spring) assemblies are essentially the
same. Except for air venting/recharging and discon-
necting/connecting air lines and electrical connection.
REMOVAL (1) Disconnect battery negative cable.
(2) Hoist vehicle and remove wheel and tire assem-
bly. (3) See AIR LINES AND FITTINGS and discon-
nect air line. (4) Disconnect electrical leads, solenoid and height
sensors. (5) See SOLENOIDS (STRUT AND AIR SPRING)
and vent air spring and remove solenoids. (6) See STRUT DAMPER ASSEMBLY in FRONT
SUSPENSION and remove strut.
DISASSEMBLY/ASSEMBLE Disassembly is restricted to upper mount and bear-
ing housing. The strut shock absorber, air spring
with integral height sensor, solenoid and wiring har-
ness are serviced as an assembly. (1) Hold retaining plate locking washer and re-
move strut rod nut. (2) Remove locking washer, retainer plate, spacer,
flat washer and mount/bearing housing assembly
(Fig. 17). (3) Assemble in reverse order. Hold retainer plate
locking washer with suitable tool and tighten strut
rod nut to 75 N Im (55 ft. lbs.) torque.
INSTALLATION (1) See STRUT DAMPER ASSEMBLY in FRONT
SUSPENSION and install strut. (2) Install solenoid, see: SOLENOIDS (STRUT
AND AIR SPRINGS). (3) Connect electrical leads, solenoid and height
sensor. (4) Charge (inflate) air spring. See RECHARGE-
AIR SPRING to activate spring solenoid and air com-
pressor. Add air for 60 seconds.
RECHARGE AIR SPRING
To activate compressor; Ground Pin S08 to Pin
X20. To Activate Spring Solenoid:
² LF: Ground Pin S31 to X20 ²
RF: Ground Pin S30 to X20
² RR: Ground Pin S32 to X20
AIR SPRINGS REAR
REMOVAL
(1) Disconnect battery negative cable, hoist vehicle
and remove wheel and tire assembly. (2) See AIR LINES AND FITTINGS and discon-
nect air line and electrical connector from solenoid. (3) See SOLENOIDS (STRUT AND AIR SPRINGS)
and vent air from spring. Remove solenoid. (4) Release upper air spring alignment/retainer
clips. (Fig. 18) (5) Remove lower spring to axle nut (Fig. 19).
(6) Pry assembly down to pull alignment studs
through retaining clips (Fig. 20). Remove assembly.
INSTALLATION
(1) Position assembly lower stud into axle seat and
upper alignment pins through frame rail adaptor. (2) Install upper retaining clips.
(3) Install lower spring to axle nut: LOOSE AS-
SEMBLE. (4) Install solenoid and connect air line and electri-
cal connector. (5) Charge (inflate) air spring. See RECHARGING
AIR SPRING and add air for 60 seconds. (6) AFTER partial air recharge tighten lower nut
Fig. 17 Air Strut Upper Mount Assembly
Ä SUSPENSION AND DRIVESHAFTS 2 - 87

to 68 N Im (50 ft. lbs.) torque.
(7) Install wheel and tire assembly. Lower vehicle,
install wheel and tire assembly and connect battery
negative cable.
RIGHT SHOCK ABSORBER (WITH HEIGHT
SENSOR)
REMOVAL
(1) Disconnect battery negative cable.
(2) Raise vehicle, see Hoisting, Group 0.
(3) Remove tire assembly.
(4) Disconnect height sensor connector located on
right rear frame rail. (5) Remove shock, see Shock Absorbers, Removal.
INSTALLATION
(1) Install shock assembly, see Shock Absorbers,
Installation. (2) Route height sensor wire through retaining
clips and then tie strap to fuel filler tube. (3) Snap height sensor connector into underbody
harness connector. (4) Install wheel/tire assembly.
(5) Height sensor wiring harness and white paint
mark on bottom shock eye must face to the front of
the vehicle (Fig. 21).
Fig. 18 Release Retaining Clips
Fig. 19 Remove/Install Lower Spring to Axle Nut
Fig. 20 Pry Assembly Out of Retaining Clips
Fig. 21 Right Rear Shock Absorber Installation
2 - 88 SUSPENSION AND DRIVESHAFTS Ä

circuits are hydraulically isolated so a leak or mal-
function in one circuit will allow continued braking
ability in the other.When force is applied to the brake pedal, the input
pushrod applies force to the boost control valve. As
the boost control valve is moved, it allows the pres-
surized fluid from the accumulator to flow into the
master cylinder booster chamber. The pressure gen-
erated in the booster chamber is directly propor-
tioned to the brake pedal force exerted by the driver.
This pressure in the booster servo in turn applies
pressure to the primary master cylinder piston that
in turn applies pressure to the secondary master cyl-
inder piston. The pressure generated in the primary
and secondary circuits are used to apply the brakes
during normal braking.
WARNING: THE HYDRAULIC ACCUMULATORS
CONTAIN BRAKE FLUID AND NITROGEN GAS AT
HIGH PRESSURE. CERTAIN PORTIONS OF THE
BRAKE SYSTEM ALSO CONTAIN BRAKE FLUID AT
HIGH PRESSURE. REMOVAL OR DISASSEMBLY
MAY RESULT IN PERSONAL INJURY AND IM-
PROPER SYSTEM OPERATION. REFER TO THE AP-
PROPRIATE SERVICE MANUAL FOR PROPER
SERVICE PROCEDURES.
HYDRAULIC BLADDER ACCUMULATOR
A Hydraulic Bladder Accumulator (Fig. 2) is used
to store brake fluid at high pressure. The pressurized
fluid is used for Anti-Lock operation and for power
assisted normal braking. The accumulator uses an
elastomeric bladder configuration with a nitrogen
pre-charge of about 6,895 kPa (1,000 psi.) With no
brake fluid in the system, the nitrogen gas pre-
charge applies approximately 6,895 kPa (1,000 psi.)
to one side of the diaphragm (Fig. 2) Under normal operation, the Pump/Motor assembly
charges the accumulator to an operating pressure of
between 11,032 and 13,790 kPa (1600 psi to 2,000
psi.) As pressurized brake fluid enters the accumula-
tor, pushing against the opposite side of the dia-
phragm, (Fig. 2) the nitrogen gas is compressed and
increases in pressure.
DUAL FUNCTION PRESSURE SWITCH
The Dual Function Pressure Switch is located on
the bottom of the hydraulic assembly (Fig. 1) and
monitors Accumulator Pressure. The Dual Function
Pressure Switch, if found to be functioning improp-
erly using the ABS diagnostics, can be replaced. See
service procedure in Electronic Components area of
On Car ABS Service in this section of the service
manual. The primary function is to control operation
of the Pump/Motor assembly and thus maintain
proper accumulator operating pressure. When accu-
mulator pressure falls to or below 11,032 kPa (1600 psi.) the pump motor switch (internal to the dual
function pressure switch) will close. This provides a
ground, through Pin 1 of the Transducer and Switch,
10 way electrical connector to the Pump/Motor relay
coil. The energized coil pulls the relay contacts
closed, providing battery voltage to run the Pump/
Motor. When Accumulator Pressure reaches 13,790
kPa (2,000 psi.) the switch opens, de-energizing the
Pump/Motor Relay that turns off the Pump/Motor. NOTE: THE (CAB) DOES NOT REGULATE
OR CONTROL ACCUMULATOR PRESSURE. The second purpose of the Dual Function Pressure
Switch is to provide a signal to the (CAB) when the
Accumulator Pressure falls below 6,895 kPa (1,000
psi). A Warning Pressure Switch, internal to the
Dual Function Pressure Switch, is normally closed
above 6,895 kPa (1,000 psi.) This sends a ground sig-
nal to pin 17 at the (CAB). At or below 6,895 kPa
(1,000 psi.) the Warning Pressure Switch opens. In-
ternally, the (CAB) (pin 17) detects 12 volts and thus
low pressure. At this warning pressure, the (CAB)
will disable the Anti-Lock Braking functions, light
the Red Brake Warning Lamp and the Amber Anti-
Lock Warning Lamp. After two minutes of continu-
ous detection, a low accumulator fault is stored. Grounding for the Dual Function Pressure Switch.
Is provided through Pin 1 of the Transducer and
Switch, 10 way electrical connector and the Modula-
tor Assembly.
PRESSURE TRANSDUCERS
Two Pressure Transducers are used for brake sys-
tem fault detection. Both transducers generate a
voltage signal (between 0.25 volts and 5.0 volts) that
is proportional to pressure. These signals are com-
Fig. 2 Hydraulic Fluid Accumulator
Ä ANTI-LOCK 10 BRAKE SYSTEM 5 - 77

In order to effectively diagnose an Anti-Lock Brake
System (ABS) condition. It is important to read Sec-
tion 1 of this manual, Anti-Lock Brake System De-
scription. This section will give you information on
the function of the ABS components. Then follow the
diagnostic procedures outlined in this section. Many conditions that generate customer com-
plaints of the ABS system may be normal operating
conditions. These conditions though are judged to be
a problem due to unfamiliarity with the ABS system.
These conditions can be recognized without perform-
ing extensive diagnostic work, given adequate under-
standing of operating principles and performance
characteristics of the ABS system. See Section 1 of
this manual to familiarize yourself with the operat-
ing principles of the ABS system.
DEFINITIONS
Several abbreviations are used in this manual.
They are presented here for reference.
² CABÐController Anti-Lock Brake
² ABSÐAnti-Lock Brake System
² PSIÐPounds per Square Inch (pressure)
² WSSÐWheel Speed Sensor
ABS CONTROLLER ANTI-LOCK BRAKE (CAB) SER-
VICE PRECAUTIONS
The ABS system uses an electronic control module,
the (CAB). This module is designed to withstand nor-
mal current draws associated with vehicle operation.
However care must be taken to avoid overloading the
(CAB) circuits. In testing for open or short circuits, do
not ground or apply voltage to any of the circuits unless
instructed to do so by the appropriate diagnostic pro-
cedure. These circuits should only be tested using a
high impedance multi-meter, special tools or the DRB
II tester 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.
ABS SYSTEM GENERAL SERVICE PRECAUTIONS
TEST DRIVING ABS COMPLAINT VEHICLES
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. Before test driving a brake complaint vehicle,
especially if the Red Brake Warning Lamp is on.
Test the brake function at low speed to be sure
that the car will stop normally. Remember that
conditions that result in illumination of the Red
Fig. 14 Decay Pressure - Hydraulic Control
5 - 88 ANTI-LOCK 10 BRAKE SYSTEM Ä

Brake Warning Lamp may indicate reduced
braking ability. The following procedure should
be used to test drive an ABS complaint:(1) Ignition on. Turn the ignition to the ON position
without starting the car and wait until the Red Brake
Warning Lamp and Amber Anti-Lock Warning Lamp
turn off. This will allow the pump to charge the
accumulator to operating pressure. If the warning
lamp(s) do not turn off, go to step 3. (2) Ignition off for 15 seconds.
(3) Start car. Wait for displays to return to normal
operating mode before proceeding. (4) With Shift lever in PARK, slowly depress brake
pedal and release. (5) Drive vehicle a short distance. During this test
drive, be sure that the vehicle achieves at least 20 mph.
Then brake to at least one complete stop and accelerate
slowly back up to at least 20 mph. (6) If a functional problem with the A.B.S. system is
determined while test driving a vehicle. Refer to the
Bendix Anti-Lock 10 Diagnostics Manual for required
test procedures and proper use of the DRB II tester.
CAUTION: The following are general precautions that
should be observed when servicing and diagnosing
the ABS system and/or other vehicle systems. Failure
to observe these precautions may result in ABS
system damage.
(1) If welding work is to be performed on the vehicle
using an arc welder, the (CAB) should be disconnected
before the welding operation begins. (2) The (CAB) and hydraulic assembly 10 way con-
nectors should never be connected or disconnected with
the ignition on. (3) Some components of the ABS system are not
serviced separately and must be serviced as complete
assemblies. Do not disassemble any component which
is designated as non-serviceable. (4) Always de-pressurize the Hydraulic Accu-
mulator when performing any work that re-
quires disconnecting any hydraulic tube, flex
hose or fitting. The ABS system uses brake fluid
at high pressure. Failure to de-pressurize the
accumulator may result in personal injury
and/or damage to painted surfaces. Brake fluid will damage painted surfaces. If brake
fluid is spilled on any painted surfaces, wash off with
water immediately.
DE-PRESSURIZING HYDRAULIC ACCUMULA- TOR
The ABS pump/motor assembly keeps the hydraulic
accumulator charged between approximately 11,032
and 13,790 kPa (1600 and 2000 psi) anytime key is in the ON position. The pump/motor assembly
cannot run if the ignition is off or either battery ca-
ble is disconnected. Unless otherwise specified, the hydraulic accumu-
lator should be de-pressurized before disassembling
any portion of the hydraulic system. The following
procedure should be used to de-pressurize the hy-
draulic accumulator: (1) With ignition off, or either battery cable discon-
nected, pump the brake pedal a minimum of 40 times
using approximately 50 pounds of pedal force. A no-
ticeable change in pedal feel will occur when the ac-
cumulator becomes discharged. (2) When a definite increase in pedal effort is felt,
pump the pedal a few additional times. This will in-
sure removal of all hydraulic pressure from the
brake system.
WHEEL SPEED SENSOR CABLES
Proper installation of wheel speed sensor cables is
critical to continued ABS system operation. Be sure
that cables are installed and routed properly. Failure
to install cables in their retainers, as shown in Sec-
tion 3 of this manual. May result in contact with
moving parts or over extension of cables, resulting in
an open circuit.
MECHANICAL DIAGNOSTICS AND SERVICE
PROCEDURES
SPECIAL SERVICE TOOLS
Some diagnostic procedures in this section require
the use of special service tools. Each of these tools is
described below.
DRB II DIAGNOSTIC TESTER
Some of the diagnostic procedures that are ex-
plained in this section require the use of the DRB II
DIAGNOSTICS TESTER to insure that proper diag-
nostics are performed. Refer to those sections for
proper testing procedures and the DRB II manual for
its proper operational information.
MST-6163 PRESSURE TESTER
Some diagnostic procedures in this manual require
the use of the MST-6163 pressure gauge and adaptor
(Fig. 2). Pressure Gauge, Special Tool MST-6163 is
required to measure accumulator pressure during
certain phases of ABS operation. The pressure gauge
and adaptor should be installed as follows: (1) De-pressurize the accumulator by pumping the
brake pedal a minimum of 40 times with the ignition
off. The procedure is fully explained under De-Pres-
surizing Hydraulic Accumulator which is described
earlier in this System Diagnosis Section.
Ä ANTI-LOCK 10 BRAKE SYSTEM 5 - 89

DRIVE-OFF CYCLE
The DRIVE-OFF CYCLE takes place when the ve-
hicle reaches about 3 miles per hour the first time af-
ter an ignition reset. During this test, the modulator
solenoid valves are activated briefly to test their
function. The DRIVE-OFF CYCLE will be bypassed
if you drive-off with the service brake pedal de-
pressed.
LATCHING VERSUS NON-LATCHING FAULTS
Some faults detected by the (CAB) are latching.
The fault is latched and (ABS) function is disabled
until the ignition switch is reset (turned OFF/ON).
Thus (ABS) function is disabled even if the original
fault has disappeared during the ignition cycle in
which it occurred. Other faults are non-latching; any
warning lights that are turned on are only on as long
as the fault condition exists. As soon as the condition
goes away. The Amber Anti-Lock Warning Light is
turned off. Although a fault code will be set in most
cases. (Example:low accumulator fault will not be
stored for a time of 2 minutes after the fault is de-
tected).
BENDIX ABS SYSTEMS DIAGNOSTICS
The Bendix Anti-Lock 10 Brake System diagnos-
tics. Beyond the basic mechanical diagnostics, sys-
tems and components covered earlier in this section,
is accomplished by using the DRB II diagnostic
tester. See testing procedures outlined in the Bendix
Anti-Lock 10 Diagnostics Manual for the 1993 M.Y. Please reference the above mentioned manual. For
any further diagnostic service procedures that are re-
quired on the Bendix Anti-Lock 10 Brake System, re-
quiring the use of the DRB II diagnostic tester.
ON CAR HYDRAULIC ABS COMPONENT SERVICE
WARNING: FAILURE TO FULLY DE-PRESSURIZE
THE HYDRAULIC ACCUMULATOR BEFORE PER-
FORMING HYDRAULIC SYSTEM SERVICE OPERA-
TIONS. COULD RESULT IN INJURY TO SERVICE
PERSONNEL AND OR DAMAGE TO PAINTED SUR-
FACES. SEE SECTION 2 FOR ADDITIONAL WARN-
INGS AND CAUTIONS.
GENERAL SERVICE PRECAUTIONS
The following are general precautions that should
be observed when servicing the Anti-Lock Brake Sys-
tem and/or other vehicle systems. Failure to observe
these precautions may result in Anti-Lock brake sys-
tem damage. If welding work is to be performed on the vehicle,
using an electric arc welder, the (CAB) connector
should be disconnected during the welding operation. The (CAB) or hydraulic assembly connector should
never be connected or disconnected with the ignition
switch in the ONposition.
Many components of the Anti-Lock brake system are
not serviceable and must be replaced as an assembly.
Do not attempt to disassemble any component
that is not designed to be a serviced component.
DE-PRESSURIZING HYDRAULIC ACCUMULA- TOR
The pump/motor assembly will keep the hydraulic
accumulator charged to approximately 11,032 and
13,790 kPa (1600 and 2000 psi) any time that the
ignition is in the ON position. The pump/motor assem-
bly cannot run if the ignition is off or if either battery
cable is disconnected. Unless otherwise specified, the hydraulic accumula-
tor should be de-pressurized before disassembling any
portion of the hydraulic system. The following proce-
dure should be used to relieve the pressure in the
hydraulic accumulator: (1) With ignition off, or either battery cable discon-
nected, pump the brake pedal a minimum of 40 times,
using approximately 222 N (50 lbs.) pedal force. A
noticeable change in pedal feel will occur, when the
accumulator is discharged. (2) When a definite increase in pedal effort is felt,
pump pedal a few additional times. This will insure
removal of all hydraulic pressure from the brake sys-
tem.
CHECKING BRAKE FLUID LEVEL
CAUTION: Use only brake fluid conforming to DOT 3
specifications such as Mopar Tor Equivalent. Do not
use any fluid in the brake hydraulic system, which
contains a petroleum base. Do not use a container
which has been used for petroleum based fluids or a
container that is wet with water. Petroleum based
fluids will cause swelling and distortion of rubber
parts in the hydraulic brake system and water will mix
with brake fluid, lowering the fluid boiling point. Keep
all brake fluid containers tightly capped to prevent
contamination.
The hydraulic assembly is equipped with a plastic
fluid reservoir, with a filter/strainer located in the filler
neck of each reservoir section. The Anti-Lock brake system requires that the hy-
draulic accumulator be de-pressurized when checking
the fluid level. To check the brake fluid level, the
following procedure should be used: (1) With the ignition off, de-pressurize the hydraulic
accumulator by applying the brake pedal approxi-
mately 40 times, using a pedal force of approximately
220 N (50 lbs.). A noticeable change in pedal feel will
occur when the accumulator is de-
Ä ANTI-LOCK 10 BRAKE SYSTEM 5 - 93

If the vehicle is not set in motion within 3 minutes
from the time the ignition switch is set in the on po-
sition. The solenoid test is bypassed but the pump/
motor is activated briefly to verify that it is
operating correctly.
WARNING SYSTEMS OPERATION
The ABS system uses an Amber Anti-Lock Warn-
ing Lamp, located in the instrument cluster. The
purpose of the warning lamp is discussed in detail
below. The Amber Anti-Lock Warning Light will turn on
when the (CAB) detects a condition which results in
a shutdown of the Anti-Lock function. The Amber
Anti-Lock Warning Lamp is normally on until the
(CAB) completes its self tests and turns the lamp off
(approximately 1-2 seconds). When the Amber Anti-
Lock Warning Light is on only the Anti-Lock func-
tion of the brake system if affected. The standard
brake system and the ability to stop the car will not
be affected when only the Amber Anti-Lock Warning
Light is on.
NORMAL OPERATION OF WARNING LAMP
With the ignition in the Crank position, the Red
Brake Warning Lamp will turn on as a bulb check.
The Amber Anti-Lock Warning Lamp will stay on for
1-2 seconds then turn off. Once verification of the self
diagnosis is completed.
ANTI-LOCK BRAKE SYSTEM COMPONENTS
The following is a detailed description of the Anti-
Lock Brake System components. For information on
servicing the Four Wheel Disk Brake System, see the
standard Brake section of this Service Manual.
MODULATOR ASSEMBLY
WARNING: THE ONLY PART OF THE MODULATOR
ASSEMBLY THAT IS A SERVICEABLE COMPONENT
IS THE DELTA P SWITCH. THE REMAINING COM-
PONENTS OF THE MODULATOR ASSEMBLY ARE
NOT SERVICEABLE ITEMS. NO ATTEMPT SHOULD
BE MADE TO REMOVE OR SERVICE ANY OTHER
PARTS OF THE MODULATOR ASSEMBLY.
The Modulator Assembly (Fig. 1) is located under
the battery tray and is covered with an acid shield.
The Modulator Assembly contains the following com-
ponents for controlling the Anti-Lock braking sys-
tem. 2 Isolation Valves, 4 Build/Decay Valves, 4
Shuttle Orifices, 2 Fluid Sumps, 2 Accumulators, a
Pump/Motor and a Pressure Differential Valve/
Switch. Also attached to the Modulator Assembly are
4 brake tubes which are connected to an 8 way con-
nector block. The connector block is mounted to the
left frame rail below the master cylinder in the same location as the non ABS equipped combination valve.
The wheel brake lines are attached to the system via
the connector block.
ISOLATION VALVES
The Isolation Valves are used to isolate the master
cylinder from the rest of the brake hydraulic circuit
during an Anti-Lock stop. Two Isolation Valves are
used, one for the primary circuit and one for the sec-
ondary circuit. The Isolation Valves are spring
loaded in the released position. In the released posi-
tion the Isolation Valves provide a fluid path from
the master cylinder outputs to the wheel brakes via
the Build/Decay valves. When actuated it provides a
fluid path from the accumulator (which was charged
by the Pump/Motor during ABS operation) to the
Build/Decay valves through the Shuttle Orifices.
BUILD/DECAY VALVES
There are 4 Build/Decay valves, one for each
wheel. In the released position they provide a fluid
path from the wheel brakes to the Isolation Valve
through the shuttle orifices. In the actuated (decay)
position, they provide a fluid path from the wheel
brakes to the sump. The Build/Decay valves are
spring loaded in the released (build) position.
SHUTTLE ORIFICE
There are 4 Shuttle Orifice Valves, one for each
wheel. The Shuttle Orifice Valve is a hydraulically
actuated valve which shuttles when the Build/Decay
valve is actuated. Actuating of the Build/Decay valve
causes a pressure differential to be created across the
Shuttle Orifice Valve. This acts like placing an ori-
fice (restriction) in the line between the Isolation
Valve and the Build/Decay Valve. This restriction
provides a controlled build rate to each wheel brake
during an Anti-Lock stop. The Shuttle Orifice Valve
will remain in the orificed position until the ABS cy-
cle is complete. When the ABS cycle has been com-
pleted the Isolation and Build/Decay valves will
return to their released position which will equalize
the pressure across the Shuttle Orifice Valves. When
the pressure equalizes, the spring loaded Shuttle Or-
ifice valves will return to the unrestricted position.
FLUID SUMPS
There are two Fluid Sumps in the Hydraulic As-
sembly, one each for the primary and secondary hy-
draulic circuits. The Fluid Sumps store the brake
fluid that is decayed from the wheel brakes during
ABS cycle. This fluid is then pumped to an accumu-
lator and/or the hydraulic system in order to provide
build pressure. The typical pressure in the sumps is
50 psi, During ABS operation only.
5 - 116 ANTI-LOCK 6 BRAKE SYSTEM Ä

In order to effectively diagnose an Anti-Lock Brake
System (ABS) condition. It is important to read Anti-
Lock Brake System Description. And to follow the
diagnostic procedures outlined in this section. Many conditions that generate customer complaints
may be normal operating conditions, but are judged to
be a problem due to not being familiar with the ABS
system. These conditions can be recognized without
performing extensive diagnostic work. Given adequate
understanding of the operating principles and perfor-
mance characteristics of the ABS system. See Section 1
of this manual to familiarize yourself with the operat-
ing principles of the ABS system.
DEFINITIONS
Several abbreviations are used in this manual. They
are presented here for reference.
² CABÐController Anti-Lock Brake
² ABSÐAnti-Lock Brake System
² PSIÐPounds per Square Inch (pressure)
² WSSÐWheel Speed Sensor
ABS COMPUTER SYSTEM SERVICE PRECAUTIONS
The ABS system uses an electronic control module,
the (CAB). This module is designed to withstand nor-
mal current draws associated with vehicle operation.
However care must be taken to avoid overloading the
(CAB) circuits. In testing for open or short circuits,
do not ground or apply voltage to any of the
circuits unless instructed to do so by the appro-
priate diagnostic procedure. These circuits should
only be tested using a high impedance multi-meter,
special tools or the DRB II tester as described in this
section. Power should never be removed or applied to
any control module with the ignition in the ON posi-
tion. Before removing or connecting battery cables,
fuses, or connectors, always turn the ignition to the
OFF position.
ABS GENERAL SERVICE PRECAUTIONS
TEST DRIVING ABS COMPLAINT VEHICLES
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. Remember conditions that result in the turn-
ing on of the Red Brake Warning Lamp may
indicate reduced braking ability. The following
procedure should be used to test drive an ABS
complaint vehicle. Before test driving a brake complaint vehicle, note
whether the Red or Amber Brake Warning Lamp is
turned on. If it is the Red Brake Warning Lamp, refer
to the standard brake, Control Valves Section in the
brake group of this manual. If the Amber Anti-Lock
Warning light was/is on, read record and erase the
fault. While the Amber ABS Warning Lamp is on the
ABS system is not functional. When the Am- ber Anti-Lock Warning Lamp is on only the Anti-Lock
function of the brake system if affected. The standard
brake system and the ability to stop the car is not be
affected if only the Amber Anti-Lock Warning Lamp is
on. (1) Turn the key to the off position and then back to
the on position. Note whether the Amber ABS Warning
Lamp continues to stay on. If it does refer to the 1993
M.Y. Bendix Anti-Lock 6 Diagnostic Manual for the
required test procedures. (2) If the Amber ABS Warning Lamp goes out, shift
into gear and drive the car to a speed of 5 mph to
complete the ABS start up cycle. If at this time the
Amber ABS Warning Lamp goes on refer to the Bendix
Anti-Lock 6 Diagnostic Manual. (3) If the Amber ABS Warning Lamp remains OUT,
drive the vehicle a short distance. During this test
drive be sure that the vehicle achieves at least 25 mph.
Brake to at least one complete stop and again acceler-
ate to 25 mph. (4) If a functional problem with the A.B.S. system is
determined while test driving a vehicle. Refer to the
Bendix Anti-Lock 6 Diagnostics Manual for required
test procedures and proper use of the DRB II tester.
ABS BRAKE SYSTEM ON VEHICLE SERVICE
The following are general precautions which
should be observed when servicing and diagnos-
ing the ABS system and/or other vehicle systems.
Failure to observe these precautions may result
in ABS system damage. (1) If welding work is to be performed on a vehicle
using an arc welder, the (CAB) should be disconnected
before the welding operation begins. (2) The (CAB) and modulator assembly 10 way con-
nector should never be connected or disconnected with
the ignition in the on position. (3) Some components of the ABS system are not
serviced separately and must be serviced as complete
assemblies. Do not disassemble any component which
is designated as non-serviceable.
CAUTION: Brake fluid will damage painted surfaces.
If brake fluid is spilled on any painted surfaces, wash
off with water immediately.
WHEEL SPEED SENSOR CABLES
Proper installation of the Wheel Speed Sensor Cables
is critical to continued system operation. Be sure that
cables are installed, routed and clipped properly. Fail-
ure to install speed sensor cables as shown in the on
car service section of this manual. May result in
contact with moving parts or over extension of cables,
resulting in component failure and an open circuit.
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As soon as the condition goes away, the Anti-Lock
Warning Light is turned off. Although a fault code
will be set in most cases.
BENDIX ABS SYSTEMS DIAGNOSTICS
Bendix Anti-Lock 6 Brake System Diagnostics, be-
yond basic mechanical diagnostics, covered earlier in
this section. Are accomplished by using the DRB II
scan tool. See testing procedures outlined in the Ben-
dix Anti-Lock 6 Diagnostics Manual for the 1992
M.Y. vehicles. Please refer to the above mentioned manual for
any further electronic diagnostics and service proce-
dures that are required on the Bendix Anti-Lock 6
Brake System.
ON-CAR ABS BRAKE SYSTEM SERVICE
GENERAL SERVICE PRECAUTIONS
The following are general cautions which should be
observed when servicing the Anti-Lock brake system
and/or other vehicle systems. Failure to observe
these precautions may result in Anti-Lock Brake
System component damage. If welding work is to be performed on the vehicle,
using an electric arc welder, the (CAB) connector
should be disconnected during the welding operation. The (CAB) connector should never be connected or
disconnected with the ignition switch in the ON po-
sition. Many components of the Anti-Lock Brake System
are not serviceable and must be replaced as an as-
sembly. Do not disassemble any component which is
not designed to be serviced.
CHECKING BRAKE FLUID LEVEL
CAUTION: Only use brake fluid conforming to DOT
3 specifications, such as Mopar or Equivalent. Do
not use any fluid which contains a petroleum base.
Do not use a container which has been used for pe-
troleum based fluids or a container which is wet
with water. Petroleum based fluids will cause swell-
ing and distortion of rubber parts in the hydraulic
brake system. Water will mix with brake fluid, low-
ering the fluid boiling point. Keep all brake fluid
containers capped to prevent contamination. Re-
move the front cap of the master cylinder reservoir
and fill to the bottom of the split ring.
For the specific procedure for the inspection of
brake fluid level and adding of brake to the reser-
voir. Refer to the Service Adjustments Section in this
group of the service manual.
BLEEDING BENDIX ANTI-LOCK 6 BRAKE SYSTEM
The Anti-Lock Brake System must be bled anytime
air is permitted to enter the hydraulic system, due to
disconnection of brake lines, hoses of components. If the Modulator Assembly is removed from the ve-
hicle, both the Base Brake System and the Anti-Lock
Brake System must be bled using the appropriate
procedures. It is important to note that excessive air
in the brake system will cause a soft or spongy feel-
ing brake pedal. During bleeding operations, be sure that the brake
fluid level remains close to the FULL level in the
reservoir. Check the fluid level periodically during
the bleeding procedure and add DOT 3 brake fluid as
required. The Bendix Anti-Lock 6 Brake System must be
bled as two independent braking systems. The non
ABS portion of the brake system is to be bled the
same as any non ABS system. Refer to the Service
Adjustments section in this manual for the proper
bleeding procedure to be used. This brake system can
be either pressure bled or manually bled. The Anti-Lock portion of brake system MUST be
bled separately. This bleeding procedure requires the
use of the DRB II Diagnostic tester and the bleeding
sequence procedure outlined below.
ABS BLEEDING PROCEDURE (FIG. 1)
(1) Assemble and install all brake system compo-
nents on vehicle making sure all hydraulic fluid
lines are installed and properly torqued. (2) Bleed the base brake system. Using the stan-
dard pressure or manual bleeding procedure as out-
lined in the Service Adjustments section of this
service manual. To perform the bleeding procedure on the ABS
unit. The battery and acid shield must be removed
from the vehicle. Reconnect the vehicles battery, to
the vehicles positive and negative battery cables us-
ing jumper cables. This is necessary to allow access
to the 4 bleeder screws located on the top of the Mod-
ulator assembly. (3) Connect the DRB II Diagnostics Tester to the
diagnostics connector. Located behind the Fuse Panel
access cover on the lower section of the dash panel to
the left of the steering column. (It is a blue 6 way
connector). (4) Using the DRB II check to make sure the
(CAB) does not have any fault codes stored. If it does
remove them using the DRB II.
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