1993 CHEVROLET DYNASTY service

earlier in this service manual supplement. Then 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.
DEFINITIONS
Several abbreviations are used in this manual. They
are presented here for reference.
² CABÐController Antilock Brake
² ABSÐAntilock Brake System
² PSIÐPounds per Square Inch (pressure)
² WSSÐWheel Speed Sensor
² ACÐAlternating Current
ABS COMPUTER SYSTEM SERVICE PRECAUTIONS
The ABS system uses an electronic control module,
the CAB. This module is designed to withstand normal
current draws associated with vehicle operation. How-
ever 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 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 position.
Before removing or connecting battery cables, fuses, or
connectors, always turn the ignition to the OFF posi-
tion.
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 the Red Brake Warning Lamp, is
turned on, refer to the base brake Control Valves
Section in the Front Wheel Drive, chassis service
manual. If the Amber Antilock Warning light was or
is on, read record and erase the faults. While the
Amber ABS Warning Lamp is on the ABS system is
not functional. The standard brake system and abil- ity to stop the car is not affected, if only the Amber
Antilock Warning Lamp is on.
(1) Turn ignition 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 1994 Bendix Antilock 4 Brake System Diagnostic
Manual for the required diagnostic test procedures. (2) If the Amber ABS Warning Lamp goes out, shift
vehicle into gear and drive car to a speed of 5 mph to
complete the ABS drive-off cycle. If at this time, the
Amber ABS Warning Lamp goes on refer to the 1994
Bendix Antilock 4 Brake System Diagnostic Manual. (3) If the Amber ABS Warning Lamp remains OUT,
continue to 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
accelerate to 25 mph. (4) If a functional problem with the ABS system is
determined while test driving a vehicle. Refer to the
Bendix Antilock 4 Brake System Diagnostics Manual
for required diagnostic 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 whenever servicing and or
diagnosing the ABS system and other vehicle
electronic systems. Failure to observe these pre-
cautions may result in ABS system damage. (1) If welding work is to be performed on a vehicle
using an arc welder. The wiring harness connector
should be disconnected from the CAB before beginning
any welding operation. (2) The CAB 60 way connector and modulator as-
sembly 10 way connector, should never be connected or
disconnected with the ignition in the on position. (3) Some components of Bendix Antilock 4 Brake
System assemblies can not be serviced separately from
the assembly and will require replacement of the
complete assembly for servicing. 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 and routing of the Wheel Speed
Sensor Cables is critical to continued system opera-
tion. Be sure that cables are installed, routed and
clipped properly. Failure to install speed sensor ca-
bles as shown in the on car service section of this
Ä ANTILOCK 4 BRAKE SYSTEM 5 - 23

manual. May result in contact with moving parts or
over extension of cables, resulting in component fail-
ure and an open circuit.
MECHANICAL DIAGNOSTICS AND SERVICE
PROCEDURES
SPECIAL SERVICE TOOL
Some diagnostic procedures in this section require
the use of the DRB diagnostics tester. The proper ap-
plication and procedures for the use of this tool are
described below.
DRB DIAGNOSTIC TESTER
Some of the diagnostic procedures that are ex-
plained in this section require the use of the DRB Di-
agnostics Tester to insure that proper diagnostics are
performed. Refer to those sections for proper testing
procedures and the DRB 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 wiring harness 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
checked and carefully reformed to increase contact
tension with its mating terminal. (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
(5) Connector push-in, spread, and corrosion.
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 set Fault code. Most failures of the ABS system will disable the
Antilock 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 it oc-
curred, if the failure condition is no longer present.
The following conditions may result in intermittent
illumination of the Amber Antilock Warning Lamp.
All other failures will cause the lamp to remain on
until the ignition switch is turned off. Circuits in-
volving these inputs to the CAB should be investi-
gated 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 Am-
ber Antilock Warning Lamp until normal system voltage is achieved. Once normal voltage is seen at
the CAB, normal operation resumes.
(2) Antilock system and pump/motor relay. If the
relays fail to make the ground circuit connection or
has an intermittent ground. The CAB will turn on
the Amber Antilock Warning Light. (3) Excess decay, an extended pressure decay pe-
riod, will turn on the Amber Antilock 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 modulator
assembly, may cause the Amber Antilock 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 Antilock Light is turned on for approximately
1- 2 seconds. Further Functional testing is accomplished once
the vehicle is set in motion, known as drive-off.
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 ANTILOCK BRAKE CAB
Fault codes are kept in a Non-Volatile memory un-
til either erased by the technician using the DRB 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 using
the DRB 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 displayed.
Most functions of the CAB and ABS system can be
accessed by the technician for testing and diagnostic
purposes by using the DRB.
5 - 24 ANTILOCK 4 BRAKE SYSTEM Ä

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.
As soon as the condition goes away, the Antilock
Warning Light is turned off. Although a fault code
will be set in most cases.
BENDIX ANTILOCK 4 BRAKE SYSTEM DIAGNOSTICS
Bendix Antilock 4 Brake System Diagnostics, be-
yond basic mechanical diagnostics, covered earlier in
this section, are accomplished by using the DRB scan
tool. See testing procedures outlined in the 1994 Ben-
dix Antilock 4 Diagnostics Manual. Please refer to the above mentioned manual for
any further electronic diagnostics and service proce-
dures that are required on the Bendix Antilock 4
Brake System.
ON-CAR ABS BRAKE SYSTEM SERVICE
GENERAL SERVICE PRECAUTIONS
The following are general cautions which should be
observed when servicing the Bendix Antilock 4
Brake System and other vehicle electronic systems.
Failure to observe these precautions may result in
Antilock Brake System component damage. If welding work is to be performed on a vehicle us-
ing an electric arc welder, disconnect the 60 way wir-
ing harness connector from the CAB, prior to
performing the welding operation. The wiring harness connector should never be con-
nected or disconnected from the CAB with the igni-
tion key in the ON or Run position. (3) Most components making up the assemblies of
the Bendix Antilock 4 Brake System can not be ser-
viced separately from those assemblies. This will re-
quire replacement of the complete assembly for the
servicing of these components. Do not disassemble
any component from an assembly which is desig-
nated as non-serviceable.
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 boiling point of the brake fluid, possibly causing brake fluid to boil resulting in brake fade.
Keep all brake fluid containers capped to prevent
contamination. Remove 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 ANTILOCK 4 BRAKE SYSTEM
The base brakes and Antilock Brake System must
be bled anytime air is permitted to enter the hydrau-
lic system, due to disconnection of brake lines, hoses
or components. If the Antilock Modulator Assembly is removed
from the vehicle, both the Base Brake System and
the Antilock Brake System must be bled using the
appropriate procedure. It is important to note that
excessive air in the brake system will cause a soft or
spongy feeling brake pedal. During brake bleeding operations, ensure that
brake fluid level remains close to the FULL level in
the reservoir. Check brake fluid level periodically
during bleeding procedure, adding DOT 3 brake fluid
as required.
CAUTION: The base brake and Antilock brake hy-
draulic systems, on the Bendix Antilock 4 Brake
System, can NOT be bled using any type of brake
pressure bleeding equipment. This type of bleeding
equipment does not develop the pressure required
in the brake hydraulic system, to adequately bleed
all trapped air. The only approved method for bleed-
ing air out of the hydraulic system on vehicles
equipped with the Bendix Antilock 4 Brake System,
is the manual procedure of pressurizing the hydrau-
lic system using constant, moderate to heavy foot
pressure on the brake pedal.
The Bendix Antilock 4 Brake System must be bled
as two independent brake systems. The non ABS por-
tion of the brake system is to be bled the same as
any non ABS system. Refer to the Service Adjust-
ments section in this manual for the proper bleeding
procedure to be used. The Bendix Antilock 4 Brake
System can only be bled using a manual method of
pressurizing the brakes hydraulic system. The Antilock portion of brake system MUST be
bled separately. This bleeding procedure requires the
use of the DRB Diagnostic tester and the bleeding se-
quence procedure outlined below.
Ä ANTILOCK 4 BRAKE SYSTEM 5 - 25

BENDIX ANTILOCK 4 MODULATOR ASSEMBLY BLEEDING PROCEDURE
(1) Assemble and install all brake system compo-
nents on the vehicle, making sure all hydraulic fluid
lines are installed and properly torqued. (2) Bleed the base brake system, using ONLYthe
bleeding procedure outlined in the Service Adjust-
ments section of this service manual supplement. To perform the bleeding procedure on the ABS modu-
lator assembly, the battery, battery tray and acid shield
must be removed from vehicle. Then reconnect the
vehicle's battery to vehicle's battery cables, using
ONLY approved battery jumper cables. (3) Connect the DRB Diagnostics Tester to the vehi-
cle's diagnostics connector. The vehicle diagnostic con-
nector is located behind the fuse panel access cover on
the lower section of the dash panel left of the steering
column. The diagnostic connector is a blue 6 way
connector. (4) Using the DRB check to make sure the CAB does
not have any stored fault codes. If it does, remove them
using the DRB.
WARNING: WHEN BLEEDING THE MODULATOR AS-
SEMBLY WEAR SAFETY GLASSES. A CLEAR BLEED
TUBE MUST BE ATTACHED TO THE MODULATOR
BLEED SCREWS AND SUBMERGED IN A CLEAR
CONTAINER FILLED PART WAY WITH FRESH CLEAN
BRAKE FLUID. DIRECT THE FLOW OF BRAKE FLUID
AWAY FROM THE PAINTED SURFACES OF THE VE-
HICLE. BRAKE FLUID AT HIGH PRESSURE MAY
COME OUT OF THE BLEEDER SCREWS, WHEN
OPENED.
When bleeding Antilock modulator assembly, the
following bleeding sequence MUSTbe followed to
insure a complete bleeding of all air from the Antilock
brake, and base brake hydraulic systems. The modu-
lator assembly can ONLY be bled using a manual
bleeding procedure to pressurize the hydraulic
system.
MODULATOR ASSEMBLY CIRCUIT BLEEDING PROCEDURE AND SEQUENCE
1 MODULATOR PRIMARY CHECK VALVE CIRCUIT
Note: To bleed hydraulic circuits of the Bendix
Antilock 4 Brake System modulator assembly,
the aid of a second mechanic or helper will be
required to pump the brake pedal. (1) Install a clear bleed tube (such as Tygon) on
primary check valve circuit bleed screw (Fig. 1). Then
install bleed tube into a clear container partially filled
with fresh clean brake fluid (Fig. 1). (2) Pump brake pedal several times, then apply and
hold a constant medium to heavy force on brake pedal. (3) Open primary check valve circuit bleed screw
(Fig. 1) at least 1 full turn to ensure an adequate flow
of brake fluid. Continue bleeding primary check valve
circuit until brake pedal bottoms. (4) After brake pedal bottoms, close and tighten
bleed screw. Then release brake pedal. Do not release
brake pedal prior to closing and tightening bleed
screw. (5) Continue bleeding modulator assembly, repeat-
ing steps 2 through 4 until a clear, bubble free flow of
brake fluid is evident. (6) When all air is bled from primary check valve
circuit, tighten bleed screw and remove bleed hose
from bleed screw. Do not remove bleed hose before
tightening bleed screw, air may re-enter modula-
tor. (7) Torque modulator assembly primary bleed screw
to9N Im (80 in. lbs.).
2 MODULATOR SECONDARY CHECK VALVE CIRCUIT (1) Move clear bleed tube to secondary check valve
circuit bleed screw (Fig. 2). Then install bleed tube into
a container partially filled with fresh clean brake fluid
(Fig. 2). (2) Pump brake pedal several times, then apply and
hold a constant medium to heavy force on brake pedal. (3) Open secondary check valve circuit bleeder screw
(Fig. 2), at least 1 full turn to ensure an adequate flow
of brake fluid. Continue to bleed secondary check valve
circuit until the brake pedal bottoms.
Fig. 1 Bleeding Modulator Assembly Primary Check Valve Circuit
5 - 26 ANTILOCK 4 BRAKE SYSTEM Ä

brake pedal. Do not release brake pedal prior to
closing and tightening bleeder screw. (6) After secondary sump bleed screw is closed, re-
move bleed hose from bleed screw. (7) Torque secondary sump bleed screw to 9 N Im (80
in. lbs.).
6 MODULATOR ASSEMBLY SECONDARY ACCUMULATOR
CIRCUIT
(8) Transfer bleed tube to secondary accumulator
bleed screw (Fig. 6). Then install bleed tube into a
container partially filled with fresh clean brake fluid
(Fig. 6).
(9) Apply constant, medium to heavy force on brake
pedal. Then using the DRB, select the bleed ABS
hydraulic unit mode, and then select the secondary
circuit valves. (The LF and RR modulator assembly
solenoids will fire for 5 seconds). (10) Open the secondary accumulator circuit bleed
screw (Fig. 6) at least one full turn. This will ensure an
adequate flow of brake fluid is expelled from the
secondary accumulator circuit. Continue to bleed pri- mary accumulator circuit, until an air-free flow of
brake fluid from the bleed screw is maintained or brake
pedal bottoms. If an air-free flow of brake fluid is not
maintained from bleed screw before brake pedal bot-
toms, close bleed screw and then repeat steps 8 and 9
until an air free flow is maintained. (11) After an air-free flow of brake fluid is main-
tained from the bleed screw, close and lightly tighten
the bleed screw. Then release force from brake pedal.
Do not release force from brake pedal prior to
closing and tightening bleeder screw. Note: For the next modulator assembly bleed-
ing procedure, use of the DRB is not required.
This step of the bleeding procedure does not
require the modulator solenoids to be operated
for bleeding to be performed. (12) Pump brake pedal several times, then apply
and hold constant medium to heavy force on brake
pedal. (13) Again without firing modulator assembly sole-
noids, open secondary accumulator circuit bleed screw
(Fig. 6) at least 1 full turn. This will ensure an
adequate flow of brake fluid is expelled from the
secondary accumulator circuit. (14) Bleed secondary accumulator circuit until a
clear, air-free flow of brake fluid is maintained from the
secondary accumulator bleed screw or the brake pedal
bottoms. If an air- free flow of brake fluid is not
maintained from secondary accumulator bleed screw
before brake pedal bottoms, repeat steps 12 and 13 of
this bleeding procedure until an air-free flow is main-
tained. (15) After an air free flow of brake fluid is main-
tained from secondary accumulator circuit bleed screw,
close and lightly tighten bleed screw. Then release
force from brake pedal. Do not release force from
brake pedal prior to closing and tightening bleed
screw. (16) After secondary accumulator bleed screw is
closed, remove bleed hose from bleed screw. (17) Torque secondary accumulator bleed screw to 9
N Im (80 in. lbs.).
PUMP/MOTOR SERVICE
On the Bendix Antilock 4 Brake System the
Pump/Motor assembly can only be serviced as part of
Modulator Assembly.
Fig. 6 Bleeding Modulator Assembly Secondary Ac- cumulator Circuit
Ä ANTILOCK 4 BRAKE SYSTEM 5 - 29

(10) Using approved battery jumper cables, attach
battery, to the vehicles negative and positive battery
cables (Fig. 17). (11) Bleed the vehicles base brake and Antilock
brake hydraulic systems. Refer to Bleeding Bendix
Antilock 4 Brake System in this service manual
supplement for required bleeding procedure. (12) Install the battery acid shield (Fig. 18) onto
modulator assembly. Be sure acid shield is securely
attached to modulator assembly before installing
battery tray. (13) Install battery tray in vehicle. Then install the 4
bolts (Fig. 19) attaching battery tray to inner fender
and frame rail. Torque the 4 attaching bolts to 20 N Im
(175 in.lbs.). (14) If equipped, install speed control vacuum reser-
voir on battery tray. Then install the 2 speed control
vacuum reservoir attaching bolts (Fig. 20). Torque the
vacuum reservoir to attaching bolts to 4 N Im (30 in.
lbs.). (15) Install battery tray access cover (Fig. 21) on
battery tray. The access cover MUST be back on
battery tray, before battery is installed in battery
tray. (16) Install battery on battery tray. Then install and
securely tighten battery hold down clamp (Fig. 22).
Then install battery heat shield, on battery (Fig. 22). (17) Install battery cables on battery. Securely
tighten clamping bolts on battery cable terminals.
Fig. 15 Hydraulic Brake Line Connections at Modulator Assembly
Fig. 16 Torquing Brake Line Connections To Modulator Assembly
Fig. 17 Battery Connected To Vehicle For Bleeding Modulator Assembly
Fig. 18 Modulator Assembly Acid Shield Installed
Ä ANTILOCK 4 BRAKE SYSTEM 5 - 33

Antilock 4 Brake System in this service manual
supplement for required bleeding procedure.(9) Install battery acid shield (Fig. 14) onto the ABS
modulator assembly. Be sure acid shield is securely
attached to modulator assembly before installing
battery tray. (10) Install battery tray into vehicle. Then install
the 4 bolts (Fig. 15) attaching battery tray to inner
fender and frame rail. Torque the 4 battery tray attach-
ing bolts to 20 N Im (175 in.lbs.).
(11) If equipped, install speed control vacuum reser-
voir on battery tray. Install the 2 speed control vacuum
reservoir attaching bolts (Fig. 16). Torque the 2
vacuum reservoir attaching bolts to 4 N Im (30 in. lbs.).
(12) Install battery tray access cover (Fig. 17) on
bottom of battery tray. The access cover MUST be
on battery tray, before battery is installed. (13) Install battery on battery tray. Then install
and securely tighten the battery hold down clamp
(Fig. 18). Then install battery heat shield, on battery
(Fig. 18). (14) Install battery cables on battery. Securely
tighten clamping bolts on battery cable terminals. (15) Reset any electrical components of the vehicle
which were affected by the removal of the battery. (16) Road test vehicle to verify correct operation of
the vehicles's base and Antilock brake systems.
Fig. 13 Battery Connected To Vehicle For Bleeding Modulator Assembly
Fig. 14 Modulator Assembly Acid Shield Installed
Fig. 11 Hydraulic Brake Line Connections atModulator Assembly
Fig. 12 Torquing Brake Line Connections To Modulator Assembly
Ä ANTILOCK 4 BRAKE SYSTEM 5 - 37

MASTER CYLINDER AND POWER BOOSTER
REMOVAL AND INSTALLATION If the Master Cylinder or Power Booster need to be
removed for replacement or servicing of other vehicle
components. Refer to Master Cylinder or Power
Brake Service section in group 5 of the 1993 M.Y.
Front Wheel Drive Car service manual. After servicing master cylinder, refer back to this
service manual supplement for the appropriate proce-
dure and sequence used to bleed the base and Anti-
lock portion of the brake system.
PROPORTIONING VALVES (FIG. 1)
CAUTION: Proportioning valves should never be
disassembled.
REMOVAL (1) Disconnect and remove both battery cables
from battery. (2) Remove heat shield (Fig. 2) from the battery.
Then remove battery hold down clamp (Fig. 2) and
battery from battery tray.
Fig. 15 Battery Tray Installation And Attaching Bolts
Fig. 16 Vacuum Reservoir Installation And Attaching Bolts
Fig. 17 Battery Tray Access Shield Installed
Fig. 18 Battery Hold Down Clamp And Heat Shield Installed
Fig. 1 ABS Proportioning Valve Identification
5 - 38 ANTILOCK 4 BRAKE SYSTEM Ä