1993 CHEVROLET DYNASTY brake light

pared by the (CAB) and used to detect brake system
faults that would require Anti -Lock Braking to be
disabled.The Boost Pressure Transducer is mounted on the
bottom of the hydraulic assembly, (Fig. 1) and moni-
tors booster servo pressure. The Primary Pressure
Transducer is mounted on the left side of the hydrau-
lic assembly and monitors primary master cylinder
pressure.
DIFFERENTIAL PRESSURE SWITCH
A non-latching Differential Pressure Switch is used
to detect a pressure difference greater than 2,068
kPa (300 psi.) between the primary and secondary
master cylinder hydraulic circuits. If detected, the
Differential Pressure Switch grounds the output of
the primary pressure transducer (circuit B-218). This
results in a 0.0 volt signal from the Primary Pres-
sure Transducer that is sensed by the (CAB) as a dif-
ferential pressure fault. The (CAB) will then light
the Red Brake Warning Lamp and the Amber Anti-
Lock Warning Lamp and disable the Anti-Lock brak-
ing function. See Fig. 1 for location of the differential
pressure switch.
PROPORTIONING VALVES
The ABS system uses screw-in Proportioning
Valves in place of the conventional Height Sensing Proportioning Valve. Each rear brake circuit has its
own screw-in Proportioning Valve that is attached to
the rear brake outlet ports of the hydraulic assembly
(Fig. 1). These valves limit brake pressure to the
rear brakes after a certain brake pressure is reached.
This improves front to rear wheel brake balance dur-
ing normal braking.
FILTERS-SERVICEABILITY
There is a screen filter in each of the two master
cylinder fill ports. There is also a low pressure filter
for the pump/motor. The filter is integral to the
Pump/Motor low pressure hose.
FLUID LEVEL SWITCH
A Low Fluid Switch is located in the hydraulic as-
sembly fluid reservoir, (Fig. 1). The switch consists of
a float and magnetic reed switch that closes when
low fluid is detected. The Low Fluid Switch is used
as an input, to the Red Brake Warning Lamp, the
(CAB), and the EVIC (if so equipped). When a low
fluid condition exists the switch will close, grounding
the low fluid circuit and illuminating the Red Brake
Warning Lamp. The (CAB) will disable the Anti-
Lock Function and light the Amber Anti-Lock Warn-
ing Lamp if vehicle is in motion above 3 mph. If
vehicle is not in motion, the Amber Anti-Lock Warn-
ing Lamp will NOT be lit.
DUAL FUNCTION PRESSURE SWITCH WIRING DIAGRAM
5 - 78 ANTI-LOCK 10 BRAKE SYSTEM Ä

The primary functions of the (CAB) are:
² (1) Detect wheel locking tendencies.
² (2) Control fluid modulation to the brakes while in
Anti-Lock mode.
² (3) Monitor the system for proper operation.
² (4) Provide communication to the DRB II while in
diagnostic mode. The (CAB) continuously monitors the speed of each
wheel, through the signals generated at the Wheel
Speed Sensors, to determine if any wheel is begin-
ning to lock. When a wheel locking tendency is de-
tected, the (CAB) will isolate the master cylinder
from the wheel brakes. This is done by activating the
Isolation Valves. The (CAB) then commands the ap-
propriate Build or Decay valves to modulate brake
fluid pressure in some or all of the hydraulic circuits.
The fluid used for modulation comes from the booster
servo circuit. The (CAB) continues to control pres-
sure in individual hydraulic circuits until a locking
tendency is no longer present. The (ABS) system is constantly monitored by the
(CAB) for proper operation. If the (CAB) detects a
fault, it can disable the Anti-Lock braking function.
Depending on the fault, the (CAB) will light one or
both of the brake warning lamps. The (CAB) contains a System Diagnostic Program
which triggers the brake system warning lamps
when a system fault is detected. Faults are stored in
a diagnostic program memory. There are 19 fault
codes that may be stored in the (CAB) and displayed
through the DRB II. These fault codes will remain in
the (CAB) memory even after the ignition has been
turned off. These fault codes will remain in memory
until they are cleared with the DRB II, or automati-
cally erased from the memory after (50) ignition
switch on/off cycles.
CONTROLLER ANTI-LOCK BRAKE (INPUTS)
² Four wheel speed sensors.
² Boost pressure transducer.
² Primary pressure transducer.
² Low fluid level switch.
² Differential pressure switch.
² Parking brake switch.
² Dual function pressure switch (warning pressure
only)
² Stop lamp switch.
² Ignition switch.
² System relay voltage.
² Ground.
² Low Accumulator
CONTROLLER ANTI-LOCK BRAKE (OUTPUTS)
²Ten modulator valves-3 decay, 3 build and 4 isola-
tion.
² Red Brake warning lamp.
² Amber Anti-Lock Warning Lamp.
² System relay actuation. ²
Diagnostic communication.
ABS SYSTEM DIAGNOSTIC CONNECTOR
The Bendix Anti-Lock system diagnostic connector
is located under the lower dash panel or in the area
of the fuse box (Fig. 8). The fuse box is located be-
hind the access panel that is on the bottom portion of
the dash panel, left of the steering column. The diag-
nostics connector is a blue 6 way connector.
ANTI-LOCK SYSTEM RELAYS AND WARNING
LAMPS
PUMP/MOTOR RELAY
Pump/Motor power is supplied by the Pump/Motor
Relay. The Pump/Motor relay is located inside the
Power Distribution Center (PDC). The relay coil is
energized by a ground from the Dual Function Pres-
sure Switch. See (Fig. 9) for the location of the pump/
motor relay in the (PDC).
SYSTEM RELAY
The (ABS) Modulator Valves and Anti-Lock Warn-
ing Lamp Relay are controlled through a System Re-
lay. The System relay is located on the top left inner
fender behind the headlight (Fig. 10). The system re-
lay provides power to the (CAB) for modulator valve
operation (pins 47 and 50) after the start-up cycle
when the ignition is turned on.
ANTI-LOCK WARNING LAMP RELAY
The Anti-Lock Warning Lamp is controlled by the
Yellow Light Relay. See (Fig. 10) for location behind
the left headlight. With the relay de-energized, the
lamp is lit. When the system relay is energized by
Fig. 8 A.B.S. Diagnostic Connector Location
5 - 82 ANTI-LOCK 10 BRAKE SYSTEM Ä

the (CAB), the Anti-Lock Warning Lamp relay is en-
ergized, and the lamp is turned off. Thus, the lamp
will be lit if the (CAB) is disconnected or if a system
fault causes (ABS) function to be turned off, or if the
system relay fails open.
ANTI-LOCK WARNING LAMP OFF
System Relay (normally open) and Yellow
Light Relay (normally closed) Energized. When the (CAB) energizes the system relay by pro-
viding 12 volts to pin 57. The voltage flow in the coil
closes the system relay. Electrical current is then
provided to pins 47 and 50 of the (CAB) to provide
power to the modulator valves. This voltage also en-
ergizes the Anti-Lock Warning Lamp Relay Switch.
This breaks the ground path to the Anti-Lock Warn-
ing Lamp and the lamp is turned off. The (CAB) by itself, also can turn on the Anti-Lock
Warning Lamp. The (CAB) can turn on the Anti-
Lock Warning Lamp by providing a ground at pin
15.
ANTI-LOCK WARNING LAMP ON
System Relay and Anti-Lock Warning Lamp
Relay De-Energized. When the Amber Anti-Lock Warning Lamp is on,
there is no current flow from the (CAB) at pin 57.
The system relay coil is NOT energized. No electrical
current flows to pins 47 and 50 (modulator valve
power), or to the Anti-Lock Warning Lamp relay coil.
Thus, the Anti-Lock Warning Lamp Relay is not en-
ergized. The Anti-Lock Warning Lamp is grounded
through the Anti-Lock Warning Lamp relay contacts.
The Anti-Lock Warning Lamp is illuminated.
Fig. 9 Pump/Motor
Fig. 10 ABS System Relay And Yellow Lamp Relay Location
Ä ANTI-LOCK 10 BRAKE SYSTEM 5 - 83

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

CONTROLLER ANTI-LOCK BRAKE (CAB)
The (CAB) (Fig. 5) is a small control computer
which receives wheel speed information, controls An-
ti-Lock operation and monitors system operation.
ANTI-LOCK BRAKES OPERATION AND
PERFORMANCE
This Anti-Lock Braking System represents the cur-
rent state-of-the-art in vehicle braking systems and
offers the driver increased safety and control during
braking. This is accomplished by a sophisticated sys-
tem of electrical and hydraulic components. As a re-
sult, there are a few performance characteristics that
may at first seem different but should be considered
normal. These characteristics are discussed below.
More technical details are discussed further in this
section.
PEDAL FEEL
Since the Bendix Anti-Lock 6 Braking System uses
the conventional Booster/Master Cylinder. The brake
pedal feel during normal braking is the same as con-
ventional Non ABS equipped cars. When Anti-Lock is activated during hard braking
due to a wheel lockup tendency. Brake pedal effort
will increase do to the master cylinder pressure be-
ing isolated from the brake system. Some brake
pedal movement and associated noises may be felt
and herd by the driver. This is normal of a Anti-Lock
Braking System due to pressurized fluid being trans-
ferred to and from the wheel brakes.
ANTI-LOCK BRAKE SYSTEM OPERATION
During Anti-Lock Braking, brake pressures are
modulated by cycling electric solenoid valves. The cy-
cling of these valves can be faintly heard as a series
of popping or ticking noises. In addition, the cycling
may be felt as a pulsation in the brake pedal, al-
though no pedal movement will be noticed. If Anti-
Lock 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 pres-
sures are modulated.
Although ABS operation is available at virtually
all vehicle speeds. It will automatically turn off at
speeds below 3 to 5 mph. Wheel lockup may be per-
ceived at the very end of an anti lock stop and is con-
sidered normal.
TIRE NOISE & MARKS
Although the ABS system prevents complete wheel
lock-up, some wheel slip is desired in order to
achieve optimum braking performance. During brake
pressure modulation, as brake pressure is increased,
wheel slip is allowed to reach up to 30%. This means
that the wheel rolling velocity is 30% 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 inter-
preted as total wheel lock-up. Complete wheel lock up normally leaves black tire
marks on dry pavement. The Anti-Lock Braking Sys-
tem will not leave dark black tire marks since the
wheel never reaches a locked condition. Tire marks
may however be noticeable as light patched marks.
VEHICLE PERFORMANCE
Anti-Lock Brakes provide the driver with some
steering control during hard braking, however there
are conditions where the system does not provide any
benefit. In particular, hydroplaning is still possible
when the tires ride on a film of water. This results in
the vehicles tires leaving the road surface rendering
the vehicle virtually uncontrollable. In addition, ex-
treme steering maneuvers at high speed or high
speed cornering beyond the limits of tire adhesion to
the road surface may cause vehicle skidding, inde-
pendent of vehicle braking. For this reason, the ABS
system is termed Anti-Lock instead of Anti-Skid.
SYSTEM SELF-DIAGNOSTICS
The Bendix Anti-Lock 6 Brake System has been
designed with the following self diagnostics capabil-
ity. The self diagnostic ABS startup cycle begins when
the ignition switch is in 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 on for approximately 1-2 seconds. Further Functional testing is accomplished once
the vehicle is set in motion. (1) The solenoid valves and the pump/motor are ac-
tivated briefly to verify function. (2) The voltage output from the wheel speed sen-
sors is verified to be within the correct operating
range.
Fig. 5 Controller Anti-Lock Brake (CAB)
Ä ANTI-LOCK 6 BRAKE SYSTEM 5 - 115

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

HYDRAULIC SPRING ACCUMULATOR
The Hydraulic Spring Accumulators (Fig. 2) (one
on each circuit) are used to store pressurized hydrau-
lic brake fluid during ABS operation only. This fluid
is used during hard braking when the ABS system is
activated, to supplement brake pressure when re-
quired. During normal Non ABS braking operation
there is NO pressurized brake fluid stored in the ac-
cumulators. The Hydraulic Spring Accumulators are
not a serviceable part of the Modulator Assembly
and should never be removed from the assembly.
PRESSURE DIFFERENTIAL VALVE/SWITCH
(DELTA P SWITCH)
The Pressure Differential Valve/Switch is located
inside the hydraulic assembly. This valve/switch func-
tions the same as the Pressure Differential
Valve/Switch located in the combination valve on stan-
dard brake systems. The delta P switch monitors the
primary and secondary hydraulic circuits for a differ-
ence in pressure. A pressure difference greater than
225 psi. Will move and latch the shuttle to ground the
Red Brake Warning Light circuit. This will in turn,
turn on the Red Brake Warning Light in the instru-
ment panel to warn the driver of a hydraulic system
problem. This Pressure Differential Valve Switch is a
replaceable item of the Modulator Assembly. The Red
Brake Warning Light indicates a problem with
the foundation brake system and not the Anti-
Lock system.
PUMP/MOTOR ASSEMBLY
The Modulator Assembly contains 2 Pump Assem-
blies, one each for the primary and secondary hydrau-
lic circuits. Both pumps are driven by a common
electric motor which is part of the Modulator Assembly.
The pumps pick up fluid from the sumps to supply
pressure to the accumulators or hydraulic system via
the isolation valves during an Anti-Lock stop. The
motor only runs during an ABS stop and is controlled
by the (CAB) via the Pump/Motor Relay. The
Pump/Motor Assembly is not a serviceable item. If it
requires service the Modulator Assembly must be re-
placed.
Fig. 1 Modulator Assembly
Fig. 2 Hydraulic Spring Accumulator
Ä ANTI-LOCK 6 BRAKE SYSTEM 5 - 117

Lamp Relay opens the Anti-Lock Warning Lamp Re-
lay switch. This breaks the ground path to the Am-
ber Anti-Lock Warning Lamp and the light is turned
off. The (CAB) by itself, also has the ability to turn on
the Amber Anti-Lock Warning Lamp. The (CAB) can
turn on the Amber Anti-Lock Warning Lamp by pro-
viding a ground at pin 15.
ANTI-LOCK WARNING LAMP ON
System Relay and Anti-Lock Warning Lamp
Relay De-Energized. When the Amber Anti-Lock Warning Lamp is on,
there is no electrical current flow from the (CAB) at
pin 57. The System Relay coil is NOT energized. No
electrical current flows to pin 47 and 41 (modulator
valve power), or to the Anti-Lock Warning Lamp Re-
lay coil. Thus, the Amber Anti-Lock Warning Lamp
is not energized. The Amber Anti-Lock Warning Lamp is grounded through the Anti-Lock Warning
Lamp Relay contacts. The Amber Anti-Lock Warning
Lamp is turned on.
HYDRAULIC CIRCUITS AND VALVE OPERATION
Through the following operation descriptions and
diagrams. The function of the various hydraulic con-
trol valves in the ABS system will be described. The
fluid control valves mentioned below, control the flow
of pressurized brake fluid to the wheel brakes during
the different modes of Anti-Lock braking. For explanation purposes we will assume all speed
sensors are sending the same wheel speed informa-
tion, requiring the same hydraulic fluid modulation
at the same rate.
NORMAL BRAKING
ISOLATION VALVES
Open to primary and secondary master cylinder
fluid supply (Fig. 1)
BUILD/DECAY VALVES Closed (Fig. 1)
The brake pedal is applied. The travel of the brake
pedal closes primary and secondary circuits from the
master cylinder fluid supply. Brake fluid from the
primary and secondary circuits flows through the
open isolation valves, through the build/decay valves
to the wheel brakes.
ABS BRAKING-BUILD PRESSURE
ISOLATION VALVES
Closed, isolating wheel brakes from master cylin-
der primary and secondary fluid supply. Through
open build valves (Fig. 2).
BUILD/DECAY VALVES Open (Fig. 2)
Fig. 11 Pump Motor Relay W/O Power Distribution Center
Ä ANTI-LOCK 6 BRAKE SYSTEM 5 - 121