steering wheel CHEVROLET DYNASTY 1993 Owner's Manual

BRAKE DISC (ROTOR) INDEX
page page
Braking Disc Removal ..................... 54
General Information ....................... 53
Inspection Diagnosis ...................... 53 Installing Braking Disc
..................... 54
Refinishing Braking Disc ................... 55
Service Procedures ....................... 53
GENERAL INFORMATION
Any servicing of the braking disc requires extreme
care to maintain the braking disc within service toler-
ances to ensure proper brake action.
CAUTION: If the braking disk (rotor) needs to be
replaced with a new part. The protective coating on
the braking surfaces of the rotor MUST BE REMOVED
with an appropriate solvent, to avoid contamination
of the brake shoe linings.
When replacing a rotor with a new part do NOT
reface the new rotor. Rotor already has the re-
quired micro finish when manufactured, only
remove the protective coating.
INSPECTION DIAGNOSIS
Before refinishing or refacing a braking disc, the disc
should be checked and inspected for the following
conditions: Braking surface scoring, rust, impregnation of lining
material and worn ridges. Excessive lateral rotor runout or wobble.
Thickness variation (Parallelism).
Dishing or distortion (Flatness).
If a vehicle has not been driven for a period of time.
The discs will rust in the area not covered by the brake
lining and cause noise and chatter when the brakes are
applied. Excessive wear and scoring of the disc can cause
temporary improper lining contact if ridges are not
removed before installation of new brake shoe assem-
blies. Some discoloration or wear of the disc surface is
normal and does not require resurfacing when linings
are replaced. Excessive runout or wobble in a disc can increase
pedal travel due to piston knock back. This will in-
crease guide pin bushing wear due to tendency of
caliper to follow disc wobble. Thickness variation in a disc can also result in pedal
pulsation, chatter and surge due to variation in brake
output. This can also be caused by excessive runout in
braking disc or hub. Dishing or distortion can be caused by extreme heat
and abuse of the brakes.
SERVICE PROCEDURES
CHECKING BRAKING DISC FOR RUNOUT AND THICKNESS
On vehicle, braking disc (rotor) runout is the com-
bination of the individual runout of the hub face and
the runout of the disc. (The hub and disc are separa-
ble). To measure runout on the vehicle, remove the
wheel and reinstall the lug nuts tightening the disc
to the hub. Mount Dial Indicator, Special Tool
C-3339 with Mounting Adaptor, Special Tool SP-1910
on steering arm. Dial indicator plunger should con-
tact disc (braking surface) approximately one inch
from edge of disc (See Fig. 1). Check lateral runout
(both sides of disc) runout should not exceed 0.13 mm
(0.005 inch).
If runout is in excess of the specification, check the
lateral runout of the hub face. Before removing disc
from hub, make a chalk mark across both the disc
and one wheel stud on the high side of runout. So
you'll know exactly how the disc and hub was origi-
nally mounted (Fig. 2). Remove disc from hub. Install Dial Indicator, Special Tool C-3339 and
Mounting Adaptor, Special Tool SP-1910 on steering
Fig. 1 Checking Braking Disc for Runout
Ä BRAKES 5 - 53

ANTI-LOCK BRAKE SYSTEMÐBENDIX ANTI-LOCK 10 AC/Y BODY INDEX
page page
ABS Brake System Diagnostic Features ....... 92
ABS Braking System Diagnosis .............. 87
ABS Controller Anti-Lock Brake (CAB) Service Precautions ........................... 88
ABS Equipped Vehicle Performance .......... 75
ABS Hydraulic Circuits and Valve Operation .... 85
ABS System Diagnostic Connector ........... 82
ABS System General Service Precautions ...... 88
ABS System Self-Diagnostics ............... 75
ABS Warning Systems Operation ............ 75
Anti-Lock Brake System Components ......... 76 Anti-Lock Brake System Definitions
........... 72
Anti-Lock Operation and Performance ......... 73
Anti-Lock System Relays and Warning Lamps . . . 82
Controller Anti-Lock Brake (CAB) ............. 80
Electronic Components ................... 103
General Information ....................... 72
General Service Precautions ................ 93
Major ABS Components ................... 73
Mechanical Diagnostics and Service Procedures . 89
Normal Braking System Function ............. 72
On Car Hydraulic ABS Component Service ..... 93
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.
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
² PSIÐPounds per Square Inch (pressure)
² WSSÐWheel Speed Sensor
NORMAL BRAKING SYSTEM FUNCTION
Under normal braking conditions, the ABS System
functions much the same as a standard brake system
with a diagonally split master cylinder. The primary
difference is that power assist is provided by hydrau-
lic power assist instead of the conventional vacuum
assist. If a wheel locking tendency is noticed 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 of the vehicle
has a set of electrical solenoid valves and hydraulic
line to provide hydraulic modulation. For vehicle sta-
bility, though both rear wheel valves receive the
same electrical signal. The system can build, hold or
reduce pressure at each wheel of the vehicle. This is
determined by the signals generated by the wheel
Four-Wheel Anti-Lock Brake System
5 - 72 ANTI-LOCK 10 BRAKE SYSTEM Ä

PUMP/MOTOR ASSEMBLY
NOTE: The (CAB) does not control the opera-
tion of the pump/motor assembly. The Pump/Motor Assembly is mounted to the tran-
saxle below the hydraulic assembly,(Fig. 3). Integral to
the Pump/Motor Assembly is an accumulator using a
sliding piston configuration with a nitrogen pre-charge
of 3,172 kPa (460 psi.) The Pump/Motor is an electri-
cally driven pump that takes low pressure brake fluid
from the hydraulic assembly fluid reservoir and pres-
surizes it. The pressurized fluid is then stored in the
piston accumulator and hydraulic bladder accumulator
for power assist and Anti-Lock Braking. Operation of
the Pump/Motor is controlled by the Dual Function
Pressure Switch through the Pump/Motor Relay. The
(CAB) does NOT control the Pump/Motor activa-
tion. Rubber isolators are used to mount the pump to
its bracket for noise isolation. The Pump/Motor Assem-
bly is connected to the Hydraulic Assembly with a low
pressure return hose and a high pressure hose. A filter
is located in the low pressure return line.
WHEEL SPEED SENSORS
One Wheel Speed Sensor (WSS), is located at each
wheel (Fig. 4, 5 and 6) and sends a small (AC) electrical
signal to the control module (CAB). This signal is
generated by magnetic induction. The magnetic induc-
tion is created when a toothed sensor ring (Tone Wheel)
passes by the stationary magnetic (Wheel Speed Sen-
sor). The (CAB) converts the (AC) electrical 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 locking. The front Wheel Speed Sensor (Fig. 4) is mounted to
a boss on the steering knuckle, for both the Front Wheel Drive and All Wheel Drive applications. The
Tone Wheel is part of the outboard constant velocity
joint housing. The Rear Wheel Speed Sensor, is mounted to the
caliper mounting adapter (Fig. 5). The rear Tone
Wheel is an integral part of the rear disc brake rotor
hub (Fig. 6). The speed sensor, to tone wheel air gap on all ap-
plications is NOT adjustable. All 4 of the vehicles, Wheel Speed Sensors are ser-
viced individually as replaceable components. The Front Wheel Drive front Tone Wheels are ser-
viced as an assembly with the front outboard con-
Fig. 3 Pump/Motor Assembly And Heat Shield
PRESSURE SWITCH AND PRESSURE TRANSDUCER WIRING
Ä ANTI-LOCK 10 BRAKE SYSTEM 5 - 79

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

SYSTEM RELAY, ANTI-LOCK WARNING LAMP RELAY AND PUMP/MOTOR RELAYS (FIG. 2)
REMOVE
See (Fig. 2) Power Distribution Center. Find the lo-
cation of the pump/motor relay in the (PDC). Remove
pump/motor relay by pulling upward and install by
pushing firmly into position. Do not twist the relay
when removing or installing it. See (Fig. 10) in the Relay And Warning Lamp Sec-
tion of this group, for the location of the Anti-Lock
system relay and the Yellow Lamp relay. Remove
the relay from the vehicle using the following proce-
dure. (1) Disconnect the wiring harness connectors from
the relays. Connectors are removed from the relays
by disengaging the connector locking tab from relay
and pulling strait off relay, do not twist. (2) Then remove the relay pack to inner fender at-
taching bolt.
INSTALL The Anti-Lock system and Yellow Lamp relay are
installed using the following procedure. (1) Mount the relay pack to the inner fender with
the anti-rotation tab on the bracket around lip of in-
ner fender hole (Fig. 10). (2) Install the relay pack to inner fender mounting
bolt and torque to 4 N Im (35 in. lbs.). (3) Connect the wiring harness connectors onto the
relays until the locking tabs on the connectors and
relays are fully engaged. Do not twist connectors when
installing them on the relays.
WHEEL SPEED SENSORS
INSPECTION
Inspect tone wheels (Fig. 3) for any missing or broken
teeth, this can cause erratic speed sensor signals.
Tone wheels should show no evidence of contact with
the wheel speed sensor. If contact was made, determine
cause and correct. Excessive runout of the tone wheels can cause erratic
wheel speed sensor signals. Replace assembly if runout
exceeds approximately 0.25 mm (0.010 inch).
FRONT WHEEL SPEED SENSOR
REMOVAL
(1) Raise vehicle and remove front wheel and tire
assembly. (2) Remove screw from clip (Fig. 4) that holds sensor
assembly grommet into fender shield. (3) Carefully, pull sensor assembly grommet from
fender shield. When removing grommet from
fender shield, do not pull on speed sensor cable. (4) Unplug speed sensor cable connector, from ve-
hicle wiring harness. (5) Remove the 2 screws (Fig. 4) that secure the
speed sensor cable, routing tube to the fender well. (6) Remove the 2 sensor assembly grommets from
the retainer bracket, on the strut damper (Fig. 4). (7) Remove speed sensor assembly to steering
knuckle attaching bolt (Fig. 4). (8) Carefully, remove sensor head from steering
knuckle. If the sensor has seized, due to corrosion, use
a hammer and punch to tap edge of sensor ear
Fig. 2 Pump/Motor and Anti-Lock System Relays
Fig. 3 Tone Wheel (Typical)
5 - 104 ANTI-LOCK 10 BRAKE SYSTEM Ä

(Fig. 5), rocking the sensor side to side until free. DO
NOT USE PLIERS ON SENSOR HEAD.
INSTALLATION (1) Connect the wheel speed sensor cable connec-
tor, to the vehicle wiring harness. (2) Push sensor assembly grommet into hole in
fender shield. Install clip and screw (Fig. 4). Torque
screw to 4 N Im (35 in. lbs.).
(3) Install speed sensor cable grommets in bracket
on strut damper (Fig. 4). (4) Install speed sensor cable routing tube to fender
well (Fig. 4). Torque both screws to 4 N Im (35 in. lbs.).
(5) Coat the speed sensor with High Temperature
Multi-purpose E.P. Grease before installing into the
steering knuckle. Install speed sensor attaching screw
and tighten to 7 N Im (60 in. lbs.)
CAUTION: Proper installation of wheel speed sensor
cables is critical to continued system operation. Be
sure that cables are routed correctly and installed in
all retainers. Failure to properly route and install
cables in retainers, as shown in this section. May
result in contact with moving parts and/or over ex-
tension of cables, resulting in an open circuit.
REAR WHEEL SPEED SENSOR (FIGS. 6 AND 8)
REMOVAL
(1) Raise vehicle and remove wheel and tire assem-
bly. (2) Remove sensor assembly grommet from under-
body and pull harness through hole in underbody. (3) Unplug connector from harness.
(4) Remove sensor grommet bracket screw from
body hose bracket, just forward of trailing arm bush-
ing. (5) Remove sensor 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.
(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 (Fig. 7) 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. Avoid
getting grease on the pickup area of the speed sensor
assembly.
Fig. 4 Front Wheel Speed Sensor Routing
Fig. 5 Removing Speed Sensor (Typical)
Ä ANTI-LOCK 10 BRAKE SYSTEM 5 - 105

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

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

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

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