CHEVROLET PLYMOUTH ACCLAIM 1993 Service Manual

INSTALL (1) Install differential pressure switch into hydrau-
lic assembly by hand, until fully threaded into hy-
draulic assembly. Then torque differential pressure
switch, into hydraulic assembly, using Socket, Spe-
cial Tool 6684, to 1.5 N Im (13 in. lbs.).
(2) Lower vehicle
(3) Connect differential pressure switch wiring
harness connector into hydraulic assembly wiring
harness (Fig. 19). (4) Connect the hydraulic assembly wiring harness
connector into the primary pressure transducer (Fig.
19). (5) Turn the ignition switch to the on position and
let the system pressurize. Check for any signs of
leakage at the differential pressure switch. (6) Fully de-pressurize the hydraulic assembly a
second time to purge any air out that may have en-
tered hydraulic assembly when the differential pres-
sure switch was removed. Turn the ignition switch to
the on position and let the system pressurize again. (7) Fill hydraulic assembly fluid reservoir to the
top of the screen on the filter rainer. Use only fresh
clean brake fluid conforming to DOT 3 requirements,
such as Mopar tor equivalent.
(8) Road test vehicle to insure that the brake sys-
tem is performing correctly.
BOOST PRESSURE TRANSDUCER
REMOVE
WARNING: FAILURE TO FULLY DE-PRESSURIZE
THE HYDRAULIC BLADDER ACCUMULATOR PRIOR
TO REMOVING BOOST PRESSURE TRANSDUCER.
MAY RESULT IN PERSONAL INJURY AND/OR DAM-
AGE TO PAINTED SURFACES OF THE VEHICLE. To remove the boost pressure transducer (Fig. 21),
from the hydraulic assembly, removal of the hydrau-
lic assembly from the vehicle is notrequired.
(1) De-pressurize hydraulic bladder accumulator on
hydraulic assembly by pumping the brake pedal a
minimum of 40 times. Refer to the procedure as de-
scribed in De-Pressurizing Hydraulic Accumulator
listed earlier in this section. (2) Raise vehicle on a frame contact type hoist. See
Hoisting in the Lubrication And Maintenance section
of this manual, for the required lifting procedure to
be used for this vehicle. (3) Disconnect hydraulic assembly wiring harness
connectors from the dual function pressure switch
and boost pressure transducer (Fig. 21). (4) Using a long extension and Socket, Special Tool
6607, remove dual function pressure switch from bot-
tom of hydraulic assembly (Fig. 22)
(5) Remove boost pressure transducer from hydrau-
lic assembly, from under vehicle using a long exten-
sion and Socket, Special Tool 6684 (Fig. 23).
Fig. 20 Differential Pressure Switch Removal And Replacement
Fig. 21 Boost Pressure Transducer Location
Fig. 22 Remove And Install Dual Function Pressure Switch
Ä ANTI-LOCK 10 BRAKE SYSTEM 5 - 111

INSTALL (1) Install boost pressure transducer (Fig. 23) into
hydraulic assembly by hand, until O-ring is fully
seated into hydraulic assembly. Then torque boost pressure transducer, into hydraulic assembly, using
Socket, Special Tool 6684, to 12 N Im (106 in. lbs.).
(2) Install Dual Function Pressure Switch (Fig. 22)
into hydraulic assembly by hand, until O-ring is
fully seated into hydraulic assembly. Then torque
dual function pressure switch, into hydraulic assem-
bly, using Socket, Special Tool 6607, to 12 N Im (106
in. lbs.). (3) Connect hydraulic assembly wiring harness
connectors, onto the dual function pressure switch
and boost pressure transducer (Fig. 21). (4) Turn the ignition switch to the on position and
let the system pressurize. Check for any signs of
leakage at the differential pressure switch. (5) Fully de-pressurize the hydraulic assembly a
second time to purge any air out that may have en-
tered hydraulic assembly when the differential pres-
sure switch was removed. Turn the ignition switch to
the on position and let the system pressurize again. (6) Fill hydraulic assembly fluid reservoir to the
top of the screen on the filter rainer. Use only fresh
clean brake fluid conforming to DOT 3 requirements,
such as Mopar tor equivalent.
(7) Road test vehicle to insure that the brake sys-
tem is performing correctly.
Fig. 23 Remove And Install Boost Pressure Transducer
5 - 112 ANTI-LOCK 10 BRAKE SYSTEM Ä

ANTI-LOCK BRAKE SYSTEMÐBENDIX ANTI-LOCK 6 AA,AG,AJ,AP BODY INDEX
page page
ABS Brake System Diagnosis .............. 123
ABS Brake System Diagnostic Features ...... 125
ABS Computer System Service Precautions . . . 124
ABS General Service Precautions ........... 124
Anti-Lock Brake System Components ........ 116
Anti-Lock Brake System Definitions .......... 113
Anti-Lock Brakes Operation and Performance . . 115
Anti-Lock System Relays and Warning Lamps . . 120
Controller Anti-Lock Brake (CAB) ............ 119
Diagnostic Connector ..................... 120
Electronic Components ................... 130 General Information
...................... 113
Hydraulic Circuits and Valve Operation ....... 121
Major Components ...................... 114
Mechanical Diagnostics and Service Procedures . 125
Normal Braking System Function ............ 114
On-Car ABS Brake System Service .......... 126
Specifications .......................... 135
System Self-Diagnostics .................. 115
Vehicle Performance ..................... 115
Warning Systems Operation ............... 116
GENERAL INFORMATION
The purpose of the Anti-Lock Brake System (ABS)
is to prevent wheel lock-up under heavy braking con-
ditions on virtually any type of road surface. Anti-
Lock Braking is desirable because a vehicle which is
stopped without locking the wheels will retain direc-
tional stability and some steering capability. This al-
lows the driver to retain greater control of the
vehicle during heavy braking. This section of the service manual covers the de-
scription, diagnostics, and on car service for the Ben-
dix Anti-Lock 6 Brake System. If other service is required on the non ABS related components of the
brake system. Refer to the appropriate section in this
group of the manual for the specific service procedure
required.
ANTI-LOCK BRAKE SYSTEM DEFINITIONS
In this section of the manual several abbreviations
are used for the components that are in the Anti-
Lock Braking System They are listed below for your
reference.
² CABÐController Anti-Lock Brake
² ABSÐAnti-Lock Brake System
Fig. 1 Four-Wheel Anti-Lock Brake System Components AA/AG/AJ Body
Ä ANTI-LOCK 6 BRAKE SYSTEM 5 - 113

² PSIÐPounds per Square Inch (pressure)
² WSSÐWheel Speed Sensor
NORMAL BRAKING SYSTEM FUNCTION
Under normal braking conditions, the ABS System
functions the same as a standard brake system with
a diagonally split master cylinder and conventional
vacuum assist. If a wheel locking tendency is detected during a
brake application, the system will enter Anti-Lock
mode. During Anti-Lock Braking, hydraulic pressure
in the four wheel circuits is modulated to prevent
any wheel from locking. Each wheel circuit is de-
signed with a set of electrical valves and hydraulic
line to provide modulation, although for vehicle sta-
bility, both rear wheel valves receive the same elec-
trical signal. The system can build or reduce
pressure at each wheel, depending on signals gener-
ated by the wheel speed sensors (WSS) at each wheel
and received at the Controller Anti-Lock Brake
(CAB).
MAJOR COMPONENTS
The following is a list of major system components.
Details of all components can be found later in this
section. See (Fig. 1) for the general location of the
components in the vehicle.
MASTER CYLINDER AND VACUUM BOOSTER
The Bendix Anti-Lock 6 Brake System uses the ve-
hicles standard Master Cylinder/Reservoir and Vac-
uum Booster (Fig. 2). The master cylinder primary
and secondary outputs go directly to the Modulator
Assembly.
MODULATOR AND PUMP MOTOR/ASSEMBLY
The Modulator Assembly (Fig. 3) contains the
wheel circuit valves used for brake pressure modula-
tion and the Pump/Motor. The Pump/Motor function, as part of the Modulator
Assembly. Is to pump low pressure brake fluid from
the brake fluid sump into the ABS Accumulator.
During a stop which requires the ABS system to be-
come operational.
WHEEL SPEED SENSORS
A Wheel Speed Sensor (Fig. 4) is located at each
wheel to transmit wheel speed information to the
Controller Anti-Lock Brake (CAB).
Fig. 2 Master Cylinder Brake Booster Assemble
Fig. 3 Modulator And Pump/Motor Assembly
Fig. 4 Wheel Speed Sensor
5 - 114 ANTI-LOCK 6 BRAKE SYSTEM Ä

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

PROPORTIONING VALVES
Two Proportioning Valves (Fig. 3) are used in the
system, one for each rear brake hydraulic circuit.
The Proportioning Valves function the same as in a
standard brake system. The Proportioning Valves are
located on the bottom of the hydraulic assembly (Fig.
1). They are the same screw in type as the ones used
on the Bendix Anti-Lock 10 and Bosh Anti-Lock
Brake systems.
WHEEL SPEED SENSORS
One Wheel Speed Sensor (WSS), is located at each
wheel (Fig. 4 and 5), and sends a small (AC) signal
to the control module (CAB). This signal is generated
by magnetic induction. The magnetic induction is
created, when a toothed sensor ring Tone Wheel (Fig.
6) passes a stationary magnetic Wheel Speed Sensor.
The (CAB) converts the (AC) signal generated at
each wheel into a digital signal. If a wheel locking
tendency is detected, the (CAB) will then modulate
hydraulic pressure to prevent the wheel(s) from lock-
ing. The front Wheel Speed Sensor is attached to a boss
in the steering knuckle (Fig. 4). The tone wheel is
part of the outboard constant velocity joint. The rear
Wheel Speed Sensor is mounted to the caliper adap-
tor (Fig. 5) and the rear tone wheel is an integral
part of the rear wheel hub (Fig. 6). The speed sensor
air gap is NOT adjustable. The four Wheel Speed Sensors are serviced individ-
ually. The front Tone Wheels are serviced as an as-
sembly with the outboard constant velocity joint. The
rear Tone Wheels are serviced as an assembly with
the rear brake hub. Correct Anti-Lock system operation is dependent
on the vehicle's wheel speed signals, that are gener-
ated by the Wheel Speed Sensors. The vehicle's
wheels and tires must all be the same size and type
to generate accurate signals. In addition, the tires
must be inflated to the recommended pressures for
optimum system operation. Variations in wheel and
tire size or significant variations in inflation pres-
sure can produce inaccurate wheel speed signals.
Fig. 3 Proportioning Valve Identification
Fig. 4 Front Wheel Speed Sensor
Fig. 5 Rear Wheel Speed Sensor
5 - 118 ANTI-LOCK 6 BRAKE SYSTEM Ä

CONTROLLER ANTI-LOCK BRAKE (CAB)
The Anti-Lock Brake Controller is a small micro-
processor based device which monitors the brake sys-
tem and controls the system while it functions in
Anti-Lock mode. The CAB is mounted on the top of
the right front frame rail and uses a 60-way system
connector (Fig. 7). The power source for the CAB is
through the ignition switch in the Run or On posi-
tion. THE CONTROLLER ANTI-LOCK BRAKE
(CAB) IS NOT ON THE CCD BUS The primary functions of the (CAB) are:
(1) Detect wheel locking tendencies.
(2) Control fluid modulation to the brakes while in
Anti-Lock mode. (3) Monitor the system for proper operation.
(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 front wheel locking tendency is
detected, 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/Decay valves to modulate brake fluid
pressure in some or all of the hydraulic circuits. The
(CAB) continues to control pressure in individual hy-
draulic 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 will turn on the Amber Anti-Lock Warning
Lamp and disable the ABS braking system. The nor-
mal Non ABS braking system will remain opera-
tional. The (CAB) contains a self-diagnostic program
which will turn on the Amber Anti-Lock Warning
Lamp when a system fault is detected. Faults are
stored in a diagnostic program memory. There are 16
fault codes which 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. The fault codes can be cleared
by using the DRB II diagnostics tester, or they will
be automatically cleared from the memory after (50)
ignition switch on/off cycles.
CONTROLLER ANTI-LOCK BRAKE (INPUTS)
² Four wheel speed sensors.
² Stop lamp switch.
² Ignition switch.
² System relay voltage.
² Ground.
² Pump/Motor Relay Monitor
² Diagnostics Communications
CONTROLLER ANTI-LOCK BRAKE (OUTPUTS)
²6 modulator valves, 4 Build/Decay and 2 isolation
valves.
² Anti-Lock warning lamp.
² System relay actuation.
² Diagnostic communication.
² Pump motor relay actuation
Fig. 6 Tone Wheel (Typical)
Fig. 7 Location Controller Anti-Lock Brake (CAB)
Ä ANTI-LOCK 6 BRAKE SYSTEM 5 - 119

DIAGNOSTIC CONNECTOR
On the AA, AG, AJ and AP bodies, the Bendix An-
ti-Lock System diagnostic connector is located under
the fuse panel access cover. The access cover is lo-
cated on the lower section of the instrument panel on
the left side of the steering column. The diagnostics
connector is a blue 6 way connector see (Fig. 8).
ANTI-LOCK SYSTEM RELAYS AND WARNING
LAMPS
SYSTEM RELAY
The (ABS) Modulator Valves and Anti-Lock Warn-
ing Lamp Relay. Are powered through a System Re-
lay located on a bracket mounted to the (CAB) see
(Fig. 9) for location of the relay. The System Relay
provides power to the (CAB) for modulator valve op-
eration (pins 47 and 41) after the startup cycle when
the ignition is turned on.
ANTI-LOCK WARNING LAMP RELAY
The Amber Anti-Lock Warning Lamp is controlled
by the Anti-Lock Warning Lamp relay. The relay is
mounted to the same bracket as the system relay at
the (CAB) see (Fig. 9). With the relay de-energized,
the lamp is lit. When the System Relay is energized
by the (CAB), the Anti-Lock warning lamp relay is
energized, and the lamp is turned off. Thus, the lamp
will be lit if the (CAB) is disconnected or if a system
fault causes the (ABS) function to be turned off.
PUMP/MOTOR RELAY
Pump/Motor power is supplied by the Pump/Motor
Relay. The Pump/Motor Relay is either mounted on
the left front inner fender shield, or the front of the
left shock tower. The mounting location is dependent
on whether the vehicle is or is not equipped with a
power distribution center. See (Fig. 10 and 11) for
specific mounting locations.
ANTI-LOCK WARNING LAMP OFF
System Relay and Anti-Lock Warning Lamp
Relay Energized From pin 57 the (CAB) energizes the system relay
coil. The electrical current flow in the coil closes the
system relay. Then electrical current is provided to
pins 47 and 41 of the (CAB) to provide power to the
modulator valves. This electrical current also ener-
gizes the Amber Anti-Lock Warning Lamp Relay
coil. The current flow in the Anti-Lock Warning
Fig. 8 A.B.S. Diagnostic Connector Location
Fig. 9 System Relay/Warning Lamp Relay
Fig. 10 Pump Motor Relay With Power Distribution Center
5 - 120 ANTI-LOCK 6 BRAKE SYSTEM Ä