1993 CHEVROLET DYNASTY wheel

ABS BRAKING-DECAY PRESSURE
ISOLATION VALVES Closed, isolating the wheel brakes from the master
cylinder primary and secondary fluid supplies (Fig.
3)
BUILD/DECAY VALVES
Open, allowing release of fluid pressure through
decay valve to the fluid reservoir. Which gets
pumped into the accumulator for the build pressure
cycle (Fig. 3).
ABS BRAKE SYSTEM DIAGNOSIS
GENERAL INFORMATION
WARNING: SOME OPERATIONS IN THIS SECTION
REQUIRE THAT HYDRAULIC TUBES, HOSES AND
FITTINGS BE DISCONNECTED FOR INSPECTION
OR TESTING PURPOSES.
CAUTION: REVIEW THIS ENTIRE SECTION PRIOR
TO PERFORMING ANY MECHANICAL WORK ON A
VEHICLE EQUIPPED WITH THE BENDIX ANTI-LOCK
6 BRAKE SYSTEM. THIS SECTION CONTAINS IN-
FORMATION ON PRECAUTIONS PERTAINING TO
POTENTIAL COMPONENT DAMAGE, VEHICLE DAM- AGE AND PERSONAL INJURY WHICH COULD RE-
SULT WHEN SERVICING AN ABS EQUIPPED
VEHICLE.
CAUTION: Certain components of the Anti-Lock
Brake System (ABS) are not intended to be serviced
individually. Attempting to remove or disconnect
certain system components, may result in personal
injury and/or improper system operation. Only
those components with approved removal and in-
stallation procedures in this manual should be ser-
viced.
This section contains information necessary to di-
agnosis mechanical conditions which can affect oper-
ation of the Bendix Anti-Lock 6 Brake System.
Specifically, this section should be used to help diag-
nose mechanical conditions which result in any of
the following: (1) Anti-Lock Warning Lamp turned on.
(2) Brakes Lock on Hard Application
Diagnosis of conditions which are obviously me-
chanical in nature. Such as brake noise, brake pulsa-
tion, lack of power assist, turning on of the Red
Brake Warning Lamp or vehicle vibration during
normal braking. Should be directed to Group 5
Brakes in this service manual. This also pertains to
problems involving the parking brake system.
Fig. 3 Decay Pressure - Hydraulic Control
Ä ANTI-LOCK 6 BRAKE SYSTEM 5 - 123

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.
5 - 124 ANTI-LOCK 6 BRAKE SYSTEM Ä

MECHANICAL DIAGNOSTICS AND SERVICE
PROCEDURES
SPECIAL SERVICE TOOL
Some diagnostic procedures in this section require
the use of the DRB II diagnostics tester. The proper
application and procedures for the use of this tool are
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 diagnostics
are performed. Refer to those sections for proper test-
ing procedures and the DRB II operators manual for
its proper operational information.
INTERMITTENT FAULTS
As with virtually any electronic system, intermit-
tent faults in the ABS system may be difficult to ac-
curately diagnose. Most intermittent faults are caused by faulty elec-
trical connections or wiring. When an intermittent
fault is encountered, check suspect circuits for: (1) Poor mating of connector halves or terminals
not fully seated in the connector body. (2) Improperly formed or damaged terminals. All
connector terminals in a suspect circuit should be
carefully reformed to increase contact tension. (3) Poor terminal to wire connection. This requires
removing the terminal from the connector body to in-
spect. (4) Pin presence in the connector assembly
If a visual check does not find the cause of the
problem, operate the car in an attempt to duplicate
the condition and record the Fault code. Most failures of the ABS system will disable Anti-
Lock function for the entire ignition cycle even if the
fault clears before key-off. There are some failure
conditions, however, which will allow ABS operation
to resume during the ignition cycle in which a fail-
ure occurred. If the failure conditions are no longer
present. The following conditions may result in inter-
mittent illumination of the Amber Anti-Lock Warn-
ing Lamp. All other failures will cause the lamp to
remain on until the ignition switch is turned off. Cir-
cuits involving these inputs to the (CAB) should be
investigated if a complaint of intermittent warning
system operation is encountered. (1) Low system voltage. If Low System Voltage is
detected by the (CAB), the (CAB) will turn on the
Amber Anti-Lock Warning Lamp until normal sys-
tem voltage is achieved. Once normal voltage is seen
at the (CAB), normal operation resumes. (2) Anti-Lock relay. If the relay fails to make the
ground circuit connection or is an intermittent
ground. The (CAB) will turn on the Amber Anti-Lock
Warning Light. (3) Excess decay, an extended pressure decay pe-
riod, will turn on the Amber Anti-Lock Warning
Light until the vehicle comes to a complete stop. Additionally, any condition which results in inter-
ruption of electrical current to the (CAB) or modula-
tor assembly. May cause the Amber Anti-Lock
Warning Lamp to turn on intermittently.
ABS BRAKE SYSTEM DIAGNOSTIC FEATURES
ABS SYSTEM SELF DIAGNOSIS
The ABS system is equipped with a self diagnostic
capability which may be used to assist in isolation of
ABS faults. The features of the self diagnostics sys-
tem are described below.
START-UP CYCLE
The self diagnostic ABS start up cycle begins when
the ignition switch is turned to the on position. An
electrical check is completed on the ABS components.
Such as Wheel Speed Sensor Continuity and System
and other Relay continuity. During this check the
Amber Anti-Lock Light is turned on for approxi-
mately 1- 2 seconds. Further Functional testing is accomplished once
the vehicle is set in motion.
² The solenoid valves and the pump/motor are acti-
vated briefly to verify function.
² The voltage output from the wheel speed sensors is
verified to be within the correct operating range. 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.
CONTROLLER ANTI-LOCK BRAKE (CAB)
Fault codes are kept in a Non-Volatile memory un-
til either erased by the technician using the DRB II
or erased automatically after 50 ignition cycles (key
ON-OFF cycles). The only fault that will not be
erased after 50 (KEY CYCLES) is the (CAB) fault. A
(CAB) fault can only be erased by the technician us-
ing the DRB II diagnostic tester. More than one fault
can be stored at a time. The number of key cycles
since the most recent fault was stored is also dis-
played. Most functions of the (CAB) and ABS system
can be accessed by the technician for testing and di-
agnostic purposes by using the DRB II.
LATCHING VERSUS NON-LATCHING ABS FAULTS
Some faults detected by the (CAB) are latching; the
fault is latched and (ABS) is disabled until the igni-
tion switch is reset. Thus ABS is disabled even if the
original fault has disappeared. Other faults are non-
latching; any warning lights that are turned on, are
only turned on as long as the fault condition exists.
Ä ANTI-LOCK 6 BRAKE SYSTEM 5 - 125

REMOVE/INSTALL PUMP MOTOR RELAY
Find the location of the Pump Motor Relay (Fig. 10
& 11), depending on whether the vehicle has or does
not have a Power Distribution Center.
(1) Hold the relay with one hand. While pulling
the relay connector strait off the relay terminals. (2) Remove the relay from the vehicle.
(3) Installation is done in the reverse order off re-
moval. Be sure that the wiring harness connector is
fully seated onto the terminals of the Pump Motor
Relay.
WHEEL SPEED SENSORS
INSPECTION
Inspect tonewheel for missing or broken teeth, this
can cause erratic sensor signals. Tonewheel should show no evidence of contact with
the wheel speed sensor. If contact was made, deter-
mine cause and correct. Excessive runout of the tonewheel can cause er-
ratic wheel speed sensor. Replace assembly if runout
exceeds approximately 0.25 mm (0.010 inch).
FRONT WHEEL SPEED SENSOR (FIG. 12)
REMOVAL
(1) Raise vehicle and remove wheel and tire as-
sembly. (2) Remove screw from grommet retainer clip that
holds the grommet into fender shield (Fig. 12). (3) Remove the 2 screws that fasten the sensor
routing tube to the frame rail. (4) Carefully, pull sensor assembly grommet from
fender shield. (5) Unplug speed sensor connector from vehicle
wiring harness. (6) Remove the sensor assembly grommets from
the retainer brackets. (7) Remove sensor head screw.
(8) Carefully, remove sensor head from steering
knuckle. If the sensor has seized, due to corrosion,
DO NOT USE PLIERS ON SENSOR HEAD. Use
a hammer and a punch and tap edge of sensor ear,
rocking the sensor side to side until free.
Fig. 10 Pump Motor Relay Location With Power Distribution Center
Fig. 11 Pump Motor Relay Location W/O PowerDistribution Center
Fig. 12 Front Wheel Speed Sensor Routing
5 - 132 ANTI-LOCK 6 BRAKE SYSTEM Ä

INSTALLATION (1) Connect the wheel speed sensor connector to
the wiring harness. (2) Push sensor assembly grommet into hole in
fender shield. Install clip and screw. (3) Install the 2 screws that fasten the speed sen-
sor routing tube to the frame rail. (4) Install sensor grommets in brackets on fender
shield and strut damper. (5) Coat the speed sensor with High Temperature
Multi-purpose E.P. Grease before installing into the
steering knuckle. Install screw tighten to 7 N Im (60
in. lbs.)
CAUTION: Proper installation of wheel speed sen-
sor cables is critical to continued system operation.
Be sure that cables are installed in retainers. Fail-
ure to install cables in retainers, as shown in this
section, may result in contact with moving parts
and/or over extension of cables, resulting in an
open circuit.
REAR WHEEL SPEED SENSOR (FIGS. 13 AND 14)
REMOVAL
(1) Raise vehicle and remove wheel and tire as-
sembly. (2) Remove sensor assembly grommet from under-
body and pull harness through hole in underbody. (3) Unplug connector from harness.
(4) Remove sensor assembly grommets from
bracket which is screwed into the body hose bracket,
just forward of trailing arm bushing (batwing brack-
et.) (5) Remove sensor and brake tube assembly clip,
located on the inboard side of trailing arm. (6) Remove sensor wire fastener from rear brake
hose bracket. (7) Remove outboard sensor assembly retainer nut.
This nut also is used to capture the brake tube clip. (8) Remove sensor head screw.
(9) Carefully, remove sensor head from adapter as-
sembly. If the sensor has seized, due to corrosion, DO
NOT USE PLIERS ON SENSOR HEAD. Use a ham-
mer and a punch and tap edge of sensor ear, rocking
the sensor side to side until free.
INSTALLATION Installation is reverse order of removal. Be sure to
coat sensor with High Temperature Multi-purpose
E.P. Grease before installing into adapter assembly.
Tighten screw to 7 N Im (60 in. lbs.) torque.
Fig. 13 Rear Wheel Speed Sensor Routing at Trailing Arm
Ä ANTI-LOCK 6 BRAKE SYSTEM 5 - 133

BRAKES
CONTENTS
page page
BENDIX ANTILOCK 4 BRAKE SYSTEM ...... 12
GENERAL INFORMATION .................. 1 HYDRAULIC SYSTEM CONTROL VALVES . . . 10
SERVICE ADJUSTMENTS
.................. 3
GENERAL INFORMATION
Throughout this group, references may be made to
a particular vehicle by letter or number designation.
A chart showing the break down of these designa-
tions is included in the Introduction Section at the
front of this service manual. Standard brake equipment consists of:
² Double pin floating caliper disc front brakes.
² Rear automatic adjusting drum brakes.
² Differential valve with a brake warning switch.
² Master cylinder.
² Vacuum power booster.
² Double pin floating caliper rear disc brakes are
available on some models. The Bendix Antilock 4 Brake System, uses the fol-
lowing standard brake system components. Master
cylinder, power booster, caliper assemblies, braking
discs, pedal assembly, brake lines and hoses. The
unique parts of the Bendix Antilock 4 Brake System
consists of the following components, modulator as-
sembly, unique proportioning valves, unique junction
block, wheel speed sensors, tone wheels, and elec-
tronic control unit. These components will be de-
scribed in detail in the Bendix Antilock 4 Brake
System section in this service manual supplement. The hydraulic system, (Fig. 1) on the Bendix Anti-
lock 4 brake system is diagonally split. Diagonally
split hydraulic brake systems, have the left front and
right rear brakes on one hydraulic system and the
right front and left rear on the other. A diagonally
split hydraulic brake system, will maintain half of
the vehicles braking capability if there is a failure in
either half of the hydraulic system. The Bendix Antilock 4 Brake System uses two
types of brake line fittings and tubing flares on the
modulator assembly (Fig. 1). The different types are
the ISO style and double wall style with their corre-
sponding fittings at different joint locations. See (Fig.
2) for specific joint locations and type of tubing
flares. CAUTION: When servicing a vehicle, sheet metal
screws, bolts or other metal fastener cannot be in-
stalled in a shock tower to take the place of any
original plastic clip. Also, NO holes can be drilled
into the front shock tower in the area shown in (Fig.
3), for installation of any metal fasteners into the
shock tower.
Because of minimum clearance in this area, (Fig.
3) installation of metal fasteners could damage the
coil spring coating and lead to a corrosion failure of
the spring. If a plastic clip is missing, lost or broken
during servicing a vehicle, replace only with the
equivalent part listed in the Mopar parts catalog.
Fig. 1 Identifying Hydraulic Brake Tubing Flares
Ä BRAKES 5 - 1

SERVICE ADJUSTMENTS INDEX
page page
Bleeding Bendix Antilock 4 Brake System ....... 3
Master Cylinder Fluid Level .................. 3 Testing for Fluid Contamination
............... 4
MASTER CYLINDER FLUID LEVEL
Check master cylinder reservoir brake fluid level a
minimum of two times a year. Master cylinder reservoirs are marked with the
words fill to bottom of rings indicating proper fluid
level (Fig. 4). Use only Mopar tbrake fluid or an equivalent from
a sealed container. Brake fluid must conform to DOT
3, specifications. Use only brake fluid that was stored in a tightly-
sealed container.
CAUTION: DO NOT use petroleum-based fluid be-
cause seal damage in the brake system will result.
CAUTION: DO NOT use brake fluid with a lower
boiling point, as brake failure could result during
prolonged hard braking.
If necessary add only an approved brake fluid to
master cylinder fluid reservoir until filled to the
proper level. Correct master cylinder fluid reservoir
fill level is to the bottom of the primary reservoir
split ring.
BLEEDING BENDIX ANTILOCK 4 BRAKE SYSTEM
CAUTION: When bleeding the Bendix Antilock 4
Brake System hydraulic circuits, refer to the Bendix
Antilock 4 Brake System bleeding procedure in this
service manual supplement.
BASE BRAKE SYSTEM BLEEDING PROCEDURE
CAUTION: The base brakes hydraulic system, on a
vehicle equipped with a Bendix Antilock 4 Brake
System, can NOT be bled using a brake hydraulic
system pressure bleeder. This type of pressure
bleeding equipment, does not develop the pressure
required in the brake hydraulic system, to ade-
quately bleed all trapped air. The only approved
method of bleeding the base brakes hydraulic sys-
tem, on vehicles equipped with a Bendix Antilock 4
Brake System, is the manual procedure of pressur-
izing the hydraulic system using constant moderate
to heavy foot pressure on the brake pedal.
When bleeding brake hydraulic systems, some air
may be trapped in brake lines or valves as far as ten
feet from the bleeder screw (Fig. 5). Therefore, it is
essential to have a fast flow of a large volume of
brake fluid when bleeding the brakes. This will en-
sure all trapped air is completely bled out of the
brakes hydraulic system.
To bleed the base brake hydraulic system. Attach a
clear plastic hose to the bleeder screw starting at the
right rear wheel and feed the hose into a clear jar
containing fresh brake fluid (Fig. 6). The following wheel sequence when bleeding the
base brakes hydraulic system should be used. This
sequence will ensure adequate removal of all trapped
air from the hydraulic system.
² Right rear wheel
² Left front wheel
Fig. 4 Master Cylinder Fluid Level
Fig. 5 Trapped Air in Brake Line
Ä BRAKES 5 - 3

² Left rear wheel
² Right front wheel
(1) Pump brake pedal three or four times, then
hold a constant moderate to heavy foot pressure on
the brake pedal.
CAUTION: Just cracking the bleeder screw often re-
stricts fluid flow, and a slow, weak fluid discharge
will NOT get all the air out.
(2) Open bleeder screw (Fig. 7) at least 1 full turn.
When bleeder screw opens, brake pedal will drop to
the floor. (3) Close bleeder screw. Release brake pedal off
floor only afterbleeder screw is completely closed.
(4) Repeat steps 1 through 3, four or five times, at
each bleeder screw. This should pass a sufficient
amount of brake hydraulic fluid to expel all trapped
air. Be sure to monitor brake fluid level in master
cylinder fluid reservoir. It must stay at a level that
will not allow air to re-enter the hydraulic system
through the master cylinder. After 4 to 8 ounces of hydraulic fluid has been bled
from the bleeder screw at this wheel, and an air-free
flow has been maintained, a good bleed is indicated. Repeat above procedure at all other remaining
bleeder screws, while checking brake pedal for travel. If brake pedal travel is still excessive or has
not improved, enough brake fluid has not passed
through the hydraulic system to expel all trapped
air. Be sure to monitor brake fluid level in the mas-
ter cylinder brake fluid reservoir. It must stay at the
proper level so air will not be allowed to re-enter the
brake system through the master cylinder. Test drive vehicle to be sure brakes are operating
correctly and that pedal is not spongy.
TESTING FOR FLUID CONTAMINATION
Indications of fluid contamination are swollen or
deteriorated rubber parts. Swollen rubber parts indicate the presence of petro-
leum in the brake fluid. To test for contamination, put small amount of
drained brake fluid in clear glass jar. If fluid sepa-
rates into layers, there is mineral oil contamination. If contaminated, drain and thoroughly flush sys-
tem. Replace master cylinder, proportioning valve,
caliper seals, wheel cylinder seals and all hoses.
Fig. 6 Proper Method for Purging Air From Brake System
Fig. 7 Open Bleeder Screw at Least One Full Turn(Typical)
5 - 4 BRAKES Ä