low oil pressure CHEVROLET PLYMOUTH ACCLAIM 1993 Service Manual

² SG service engine oil is a high quality crankcase
lubricant designed for use in all naturally aspirated
engines. If SG service engine oil is used in turbo-
charged engine, change engine oil at every 4 800
km (3,000 miles) or three months.
² SG/CD service engine oil is a high quality crank-
case lubricant designed for use in most naturally as-
pirated and turbocharged gasoline or diesel engines.
FLEXIBLE FUEL VEHICLES
Vehicles operated using Flexible Fuel (M85) re-
quire engine oil that meet or exceed Chrysler Stan-
dard MS-9214. Mopar Flexible Fuel engine oil or
equivalent should be used when adding or changing
crankcase lubricant. The API symbol (Fig. 1) on the
container indicates the viscosity grade, quality and
fuel economy ratings of the lubricant it contains. Use
ENERGY CONSERVING II motor oil with API SER-
VICE SG or SG/CD classification.
ENGINE OIL ADDITIVES
Chrysler Corporation recommends that Mopar En-
gine Oil Supplement or equivalent be used when fric-
tion and corrosion reducing materials added to the
crankcase lubricant is desired.
CRANKCASE OIL LEVEL INSPECTION
CAUTION: Do not overfill crankcase with engine oil,
oil foaming and oil pressure loss can result.
Inspect engine oil level approximately every 800
kilometers (500 miles). Position vehicle on level sur- face. With engine OFF, allow enough time for oil to
settle to bottom of crankcase, remove engine oil level
indicator (dipstick) and wipe clean. Install dipstick
and verify it is seated in the tube. Remove dipstick,
with handle above tip, take oil level reading (Fig. 2).
Add oil only if level is below MIN or ADD mark on
dipstick.
ENGINE OIL CHANGE
Change engine oil at mileage and time intervals
described in Lubrication and Maintenance Schedules.
Position the vehicle on a level surface. Hoist and
support vehicle on safety stands. Refer to Hoisting
and Jacking Recommendations in this group. Place a
suitable 3.8 liter (4 qt.) drain pan under crankcase
drain. Remove drain plug from crankcase. Inspect
drain plug threads for stretching or other damage.
Replace drain plug and gasket if damaged. Install
drain plug in crankcase. Lower vehicle and fill
crankcase with specified type and amount of engine
oil described in this section. Start engine and inspect
for leaks. Stop engine and inspect oil level.
ENGINE OIL FILTER
SELECTING OIL FILTER
Chrysler Corporation recommends a Mopar or
equivalent oil filter be used when replacement is re-
quired. A replacement filter must be designed to
withstand 1756 kPa (256 psi) of internal pressure.
OIL FILTER REPLACEMENT
Position a drain pan under the oil filter. Using a
suitable oil filter wrench (Fig. 3) loosen filter. When
filter separates from adapter nipple, tip gasket end
upward to minimize oil spill. Remove filter from ve-
hicle. With a wiping cloth, clean the gasket sealing
surface (Fig. 4) of oil and grime. Wipe off oil residue
from below oil filter adapter.
TO INSTALL NEW OIL FILTER: Lightly lubricate oil filter gasket with engine oil or
chassis grease. Thread filter onto adapter nipple.
When gasket makes contact with sealing surface,
tighten filter one full turn. If necessary use a filter
wrench, do not over tighten. Add oil, verify crank-
case oil level and start engine. Inspect for oil leaks.
RECOMMENDED VISCOSITY GRADES
Fig. 1 API Symbol
Fig. 2 Oil Level Indicator DipstickÐTypical
Ä LUBRICATION AND MAINTENANCE 0 - 9

ENGINE COOLING SYSTEM
WARNINGS AND PRECAUTIONS
WARNING: ANTIFREEZE IS AN ETHYLENE GLYCOL
BASE COOLANT AND IS HARMFUL IF SWAL-
LOWED OR INHALED. IF SWALLOWED, DRINK
TWO GLASSES OF WATER AND INDUCE VOMIT-
ING. IF INHALED, MOVE TO FRESH AIR AREA.
SEEK MEDICAL ATTENTION IMMEDIATELY. DO
NOT STORE IN OPEN OR UNMARKED CONTAIN-
ERS. WASH SKIN AND CLOTHING THOROUGHLY
AFTER COMING IN CONTACT WITH ETHYLENE
GLYCOL. KEEP OUT OF REACH OF CHILDREN. DISPOSE OF GLYCOL BASE COOLANT PROP-
ERLY, CONTACT YOUR DEALER OR GOVERNMENT
AGENCY FOR LOCATION OF COLLECTION CEN-
TER IN YOUR AREA. DO NOT OPEN A COOLING SYSTEM WHEN THE
ENGINE IS AT RUNNING TEMPERATURE, PER-
SONAL INJURY CAN RESULT. AVOID RADIATOR COOLING FAN WHEN ENGINE
COMPARTMENT RELATED SERVICE IS PER-
FORMED, PERSONAL INJURY CAN RESULT.
CAUTION: Do not use straight antifreeze as engine
coolant, inadequate engine running temperatures
can result. Do not operate vehicle without proper concentra-
tion of recommended ethylene glycol coolant, high
running temperatures and cooling system corrosion
can result.
The engine cooling system will develop internal
pressure of 97 to 123 kPa (14 to 18 psi) at normal op-
erating temperature. Allow the vehicle approxi-
mately one half hour to cool off before opening the
cooling system. As an indicator of pressure, squeeze
the upper radiator hose between index finger and
thumb. If it collapses with little effort the system
would have low internal pressure and should be safe
to open to the first safety notch of the radiator cap.
Refer to Group 7, Cooling System.
COOLING SYSTEM INSPECTION
Coolant level (Fig. 5) should be inspected when
other engine compartment service is performed or
when coolant leak is suspected. Coolant recovery
tank level should read between the MIN and MAX
marks, located on the side of recovery tank, when the
engine is at normal operating temperature. Normal
coolant level maintenance does not require the re-
moval of radiator cap. Cooling system freeze protec-
tion should be tested at the onset of the winter
season or every 12 months. Service is required if
coolant is low, contaminated, rusty or freeze protec-
tion is inadequate. To properly test cooling system,
see Group 7, Cooling System.
The cooling system factory fill is a mixture of 50%
Glycol based antifreeze and 50% water. Using a suit-
able hydrometer, measure antifreeze concentration in
the radiator when the engine is cool. If the cooling
system has recently been serviced, allow coolant to
circulate for at least 20 minutes before taking hy-
drometer reading. Properly mixed coolant will pro-
tect the cooling system to -37ÉC (-35ÉF). If the freeze
protection is above -28ÉC (-20ÉF), drain enough cool-
ant from the cooling system to allow room to add an-
Fig. 3 Remove Oil Filter
Fig. 4 Install Oil Filter
Fig. 5 Coolant Recovery Tank
0 - 10 LUBRICATION AND MAINTENANCE Ä

tifreeze to achieve adequate protection. A mix table
on the coolant container indicates the amount of an-
tifreeze required to winterize the cooling system
based on the capacity, see Capacity Chart in General
Information section of this group.
SELECTING ANTIFREEZE
Chrysler Corporation recommends Mopar Anti-
freeze/Summer Coolant, or equivalent be used to win-
terize and protect cooling system.
RADIATOR CAP
The radiator cap must be secure to provide proper
pressure release and coolant recovery. Inspect and
test radiator cap when cooling system service is per-
formed or when problem is suspected.
COOLING SYSTEM SERVICE
The cooling system should be drained, flushed and
filled with the proper coolant mixture at the inter-
vals described in the Lubrication and Maintenance
Schedules. Refer to General Information section of
this group. For proper service instructions see Group
7, Cooling System.
ENGINE AIR CLEANER
The engine air cleaner should be serviced at the in-
tervals described in the Lubrication and Mainte-
nance Schedules. Refer to General Information
section of this group. Additional information can be
found in Group 14, Fuel System and Group 25, Emis-
sion System. Inspect all air cleaner hoses or tubes for
damage or leaks when other engine compartment
service is performed. Replace faulty components.
AIR CLEANER SERVICE
CAUTION: The air cleaner cover must be installed
properly for the emissions system and engine con-
troller to function correctly. Do not immerse paper air filter element or temper-
ature sensor in cleaning solvents, damage can re-
sult.
TO SERVICE AIR CLEANER ASSEMBLY: (1) Raise hood of vehicle and inspect all air cleaner
components for damage or improper attachment. (2) Remove air cleaner cover (Fig. 6, 7, 8, 9, or 10).
(3) Remove paper air filter element from air
cleaner body. Hold a shop light on throttle body side
of element. Inspect air intake side of element. If light
is visible through element, blow dust from element
(Fig. 11) and reuse. If element is saturated with oil
or light is not visible, replace filter. If element is sat-
urated with oil, perform crankcase ventilation sys-
tem tests. (4) Remove fiber crankcase filter (Fig. 6, 7, 8, 9, or
10) and clean with solvent, squeeze filter dry and ap- ply small amount of engine oil. If a metallic mesh is
used to retain fiber filter, clean mesh with solvent
and reuse.
(5) Clean inside of air cleaner cover and body with
vacuum or compressed air. If oily, wash with solvent. To Install, reverse the preceding operation.
Fig. 6 Air CleanerÐ3.0L Engine
Fig. 7 Air CleanerÐFlexible Fuel Engine
Fig. 8 Air CleanerÐ16 Valve Engine
Ä LUBRICATION AND MAINTENANCE 0 - 11

BRAKE RESERVOIR LEVEL INSPECTION
WARNING: DO NOT ALLOW PETROLEUM OR WATER
BASE LIQUIDS TO CONTAMINATE BRAKE FLUID,
SEAL DAMAGE AND BRAKE FAILURE CAN RESULT.
RELIEVE PRESSURE IN ANTI-LOCK BRAKE SYS-
TEM BEFORE ADDING BRAKE FLUID TO RESER-
VOIR. IF NOT, BRAKE FLUID COULD DISCHARGED
FROM THE RESERVOIR POSSIBLY CAUSING PER-
SONAL INJURY.
The brake reservoir level should be inspected when
other under hood service is performed. It is normal
for the reservoir level to drop as disc brake pads
wear. When fluid must be added, use Mopar, Brake
Fluid or equivalent. Use only brake fluid conforming
to DOT 3, Federal, Department of Transportation
specification. To avoid brake fluid contamination, use
fluid from a properly sealed container. On vehicles with anti-lock brakes, depressurize the
system before inspecting fluid level. Turn OFF the
ignition and remove the key. Pump the brake pedal
at least 50 times to relieve the pressure in the sys-
tem.
On all vehicles, if fluid should become low after sev-
eral thousand kilometers (miles), fill the reservoir to
level marks on the side of the reservoir (Fig. 8 or 9).
HEADLAMPS
The headlamps should be inspected for intensity
and aim whenever a problem is suspected. When lug-
gage compartment is heavily loaded, the headlamp
aim should be adjusted to compensate for vehicle
height change. For proper service procedures, refer to
Group 8L, Lamps. DRIVER SUPPLEMENTAL AIRBAG SYSTEM
If the AIRBAG indicator lamp does not light at all,
stays lit or lights momentarily or continuously while
driving, a malfunction may have occurred. Prompt service is required. Refer to Group 8M, Restraint
Systems for proper diagnostic procedures.
BODY LUBRICATION
Body mechanisms and linkages should be inspected,
cleaned and lubricated as required to maintain ease of
operation and to prevent corrosion and wear. Before a component is lubricated, oil, grease and dirt
should be wiped off. If necessary, use solvent to clean
component to be lubricated. After lubrication is com-
plete, wipe off excess grease or oil. During winter season, external lock cylinders should
be lubricated with Mopar, Lock Lubricant or equiva-
lent to ensure proper operation when exposed to water
and ice. To assure proper hood latching component operation,
use engine oil to lubricate the lock, safety catch and
hood hinges when other under hood service is per-
formed. Mopar, Multi-purpose Grease or equivalent
should be applied sparingly to all pivot and slide
contact areas.
USE ENGINE OIL ON:
² Door hingesÐHinge pin and pivot points.
² Hood hingesÐPivot points.
² Luggage compartment lid hingesÐPivot points.
USE MOPAR LUBRIPLATE OR EQUIVALENT ON:
² Door check straps.
² Hood counterbalance springs.
² Luggage compartment lid latches.
² Luggage compartment lid prop rod pivots.
² Ash tray slides.
² Fuel Fill Door latch mechanism.
² Park brake mechanism.
² Front seat tracks.
Fig. 8 Anti-lock Brake Reservoir
Fig. 9 Master Cylinder Brake ReservoirÐExcept
Anti-lock
0 - 22 LUBRICATION AND MAINTENANCE Ä

FRONT SUSPENSION SERVICE PROCEDURES INDEX
page page
Ball Joints .............................. 13
Hub and Bearing Assembly ................. 20
Knuckle (Front Suspension) ................. 16
Lower Control Arm ....................... 10
Lower Control Arm Pivot Bushings ........... 11 Shock Absorbers (Strut Damper)
............. 10
Strut Damper Assembly ..................... 7
Suspension Coil Springs .................... 9
Sway Bar .............................. 14
Wheel Alignment .......................... 5
WHEEL ALIGNMENT
Front wheel alignment is the proper adjustment of
all interrelated front suspension angles. These angles
are what affects the running and steering of the
front wheels of the vehicle. The method of checking front alignment will vary
depending on the type of equipment being used. The
instructions furnished by the manufacturer of the
equipment should always be followed. With the ex-
ception that the alignment specifications recom-
mended by Chrysler Corporation be used. There are six basic factors which are the founda-
tion to front wheel alignment. These are height,
caster, camber, toe-in, steering axis inclination and
toe-out on turns. Of the six basic factors only camber
and toe in are mechanically adjustable (Fig. 1)
CAUTION: Do not attempt to modify any suspen-
sion or steering components by heating or bending
of the component.
Wheel alignment adjustments and checks should be
made in the following sequence. (1) Camber
(2) Toe
Camber is the number of degrees the top of the
wheel is tilted inward or outward from true vertical.
Inward tilt is negative camber. Outward tilt is posi-
tive camber. Excessive camber is a tire wear factor: negative
camber causes wear on the inside of the tire, while
positive camber causes wear to the outside. Toe
is measured in degrees or inches and is the
distance the front edges of the tires are closer (or far-
ther apart) than the rear edges. See Front Wheel
Drive Specifications for Toesettings.
PRE-ALIGNMENT
Before any attempt is made to change or correct
the wheel alignment factors. The following inspection
and necessary corrections must be made on those
parts which influence the steering of the vehicle. (1) Check and inflate tires to recommended pres-
sure. All tires should be the same size and in good
condition and have approximately the same wear.
Note type of tread wear which will aid in diagnosing,
see Wheels and Tires, Group 22. (2) Check front wheel and tire assembly for radial
runout. (3) Inspect lower ball joints and all steering link-
age for looseness. (4) Check for broken or sagged front and rear
springs. Front suspension must only be checked after the
vehicle has had the following checked or adjusted.
Tires set to recommended pressures, full tank of fuel,
no passenger or luggage compartment load and is on
a level floor or alignment rack. Just prior to each alignment reading. The vehicle
should be bounced (rear first, then front) by grasping
bumper at center and jouncing each end an equal
number of times. Always release bumpers at bottom
of down cycle.
Ä SUSPENSION AND DRIVESHAFTS 2 - 5

FRONT AND REAR AIR SPRINGS
The front and rear air springs are essentially pneu-
matic cylinders that replace the steel coil springs.
The air filled springs allow the vehicle suspension
height to be adjusted for all weight conditions. The air springs allow for the reduction of spring
rates to improve vehicle ride characteristics.
FRONT/REAR SPRING SOLENOIDS
The front and rear solenoids control air flow in and
out of the front and rear springs. The Air Suspension
Control Module (ASCM) opens the solenoids when
the system requires air to be added to or exhausted
from the air springs. The solenoids operate at a cur-
rent draw range of 0.6 to 1.5 amps.
HEIGHT SENSOR
A magnetic switch type sensor. Located in the
right rear shock absorber and left and right front
struts, (Fig. 2) monitors vehicle height. The sensors
transmit signals to the (ASCM) relating to vehicle
height status (low, trim, medium, high).
CONTROL MODULE
The Air Suspension Control Module (ASCM). Is a
device that controls the ground circuits for the Com-
pressor Relay, Compressor Exhaust Solenoid Valve
and Front and Rear Solenoid Valves. The (ASCM)
limits the compressor pump operation time to 170 to
190 seconds. This controlled operation time is to pre- vent damage to the compressor motor.
To prevent excessive cycling between the compres-
sor and the exhaust solenoid circuits during normal
ride conditions. A 14 to 16 second delay is incorpo-
rated in the microprocessor logic. The system is non-operation when one of the fol-
lowing conditions exists. A door(s) is/are open, the
trunk is open, the service brake is applied or the
throttle position sensor is 65% to 100% open. System
operation is inhibited during high speed cornering
activities or if there is a charging system failure.
The control module is on the CCD bus system.
COMPRESSOR ASSEMBLY
The compressor assembly is driven by an electric
motor and supplies air pressure between 930 to 1241
kPa (135 to 180 psi) (Fig. 3). A solenoid operated ex-
haust valve. Located in the compressor head assem-
bly, releases air when energized. A heat actuated circuit breaker. Located inside the
compressor motor housing. Is used to prevent damage
to the compressor motor in case of control module
failure.
COMPRESSOR AIR DRYER
The air dryer is attached to the compressor (Fig. 3).
This component serves two purposes. It absorbs mois-
ture from the atmosphere before it enters the system
Fig. 2 Front and Rear Air Springs
2 - 74 SUSPENSION AND DRIVESHAFTS Ä

expel all the trapped air. Be sure to monitor the fluid
level in the pressure bleeder. It must stay at the
proper level so air will not be allowed to reenter the
brake system through the master cylinder.
BLEEDING WITHOUT A PRESSURE BLEEDER
If a pressure bleeder is not available. A good brake
fluid flow can be obtained by manual bleeding of the
brake hydraulic system, following these steps. Manual bleeding of the brakes hydraulic sys-
tem will require the aid of a helper to correctly
perform manual brake bleeding procedure. The following wheel sequence for bleeding the
brake hydraulic system should be used to ensure ad-
equate removal of all trapped air from the hydraulic
system. ²
Right rear wheel
² Left front wheel
² Left rear wheel
² Right front wheel
(1) Pump the brake pedal three or four times and
hold it down before the bleeder screw is opened. (2) Then open the bleeder screw at least 1 full
turn. When the bleeder screw opens the brake pedal
will drop all the way to the floor. (3) Release the brake pedal only afterthe bleeder
screw is closed. (4) Repeat steps 1 through 3, four or five times, at
each bleeder screw. This should pass a sufficient
amount of fluid to expel all the trapped air from the
brake system. Be sure to monitor the fluid level in
the master cylinder, so it stays at a proper level so
air will not reenter the brake system through the
master cylinder. Test drive vehicle to be sure brakes are operating
correctly and that pedal is solid.
TEST FOR FLUID CONTAMINATION
Indications of fluid contamination are swollen or
deteriorated rubber parts. Swollen rubber parts indicate the presence of petro-
leum in the brake fluid. To test for contamination, put small amount of
drained brake fluid in clear glass jar. If fluid sepa-
rates into layers, there is mineral oil contamination. If contaminated, drain and thoroughly flush sys-
tem. Replace master cylinder, proportioning valve,
caliper seals, wheel cylinder seals and all hoses.
WHEEL STUD NUT TIGHTENING
When tightening wheel stud nuts, a criss-cross
tightening sequence should be followed (Fig. 9).
Tighten all stud nuts to one-half specified torque.
Repeat, fully tightening to 129 N Im (95 ft. lbs.).
Fig. 9 Wheel Stud Nut Tightening Sequence
Fig. 7 Proper Method for Purging Air From Brake
System (Typical)
Fig. 8 Open Bleeder Screw at Least One Full Turn (Typical)
Ä BRAKES 5 - 7

seal, a new seal should be used when reinstalling the
inner bearing. (See Fig. 1) (5) Thoroughly clean all old grease from the outer
and inner bearings, bearing cups and hub cavity (See
Fig. 1). To clean bearings, soak them in an ap-
propriate cleaning solvent. Strike the flat sur-
face of the bearing inner race against a
hardwood block several times. Immerse the
bearings in solvent between the blows to jar
grease loose and wash old particles of hardened
grease from bearings. Repeat this operation un-
til bearings are clean. Bearings can be dried
using compressed air but do not spin the bear-
ings. After cleaning, oil the bearings with engine
oil. Insert the bearing into its appropriate cup,
apply pressure to the bearing while rotating it to
test them for pitting and roughness. Replace all
worn or defective bearings. If bearing shows signs of pitting or roughness they should be
replaced. Bearings must be replaced as a set,
both the cup and the bearing need to be replaced
at the same time. If bearings are suitable for
further use, remove engine oil from bearings
using appropriate solvent and dry bearings. Re-
pack the bearings using a Multi-Purpose NLGI.
Grade 2 EP Grease such as Mopar or equivalent,
and place them in a clean covered container
until ready for installation. If a bearing packer is
not available, hand pack grease into all cavities
between bearing cage and rollers. (6) If bearings and cups are to be replaced, remove
cups from the drum or hub using a brass drift or
suitable remover. (7) Replace bearing cups with appropriate installing
tool. (8) Install inner bearing in grease coated hub and
bearing cup, and install new grease seals using the
appropriate seal installer. (9) Coat hub cavity and cup with grease.
(10) Before installing hub or drum assembly, inspect
stub axle and seal surface for burrs or roughness, and
smooth out all rough surfaces. (11) Coat the stub axle with Multi-Purpose NLGI,
Grade 2 EP grease such as Mopar or equivalent. (12) Carefully slide the hub of drum assembly onto
the stub axle. Do not drag seal or inner bearing
over the threaded area of the stub axle. (13) Install outer bearing, thrust washer and nut.
(14) Tighten the wheel bearing adjusting nut to 27 to
34 N Im (240 to 300 in. lbs.) while rotating hub or drum
assembly. This seats the bearings. (15) Back off adjusting nut 1/4 turn (90É) then
tighten adjusting nut only finger tight. (16) Position the nut lock over the bearing adjusting
nut with one pair of slots in line with the cotter pin hole
in the stub axle, and install cotter pin. (17) Install the grease caps and the wheel and tire
assemblies. Tighten wheel stud nuts to 115 N Im (85 ft.
lbs.) on all models. reinstall wheel covers if so
equipped.
Fig. 1 Rear Wheel Bearings
Ä BRAKES 5 - 71

circuits are hydraulically isolated so a leak or mal-
function in one circuit will allow continued braking
ability in the other.When force is applied to the brake pedal, the input
pushrod applies force to the boost control valve. As
the boost control valve is moved, it allows the pres-
surized fluid from the accumulator to flow into the
master cylinder booster chamber. The pressure gen-
erated in the booster chamber is directly propor-
tioned to the brake pedal force exerted by the driver.
This pressure in the booster servo in turn applies
pressure to the primary master cylinder piston that
in turn applies pressure to the secondary master cyl-
inder piston. The pressure generated in the primary
and secondary circuits are used to apply the brakes
during normal braking.
WARNING: THE HYDRAULIC ACCUMULATORS
CONTAIN BRAKE FLUID AND NITROGEN GAS AT
HIGH PRESSURE. CERTAIN PORTIONS OF THE
BRAKE SYSTEM ALSO CONTAIN BRAKE FLUID AT
HIGH PRESSURE. REMOVAL OR DISASSEMBLY
MAY RESULT IN PERSONAL INJURY AND IM-
PROPER SYSTEM OPERATION. REFER TO THE AP-
PROPRIATE SERVICE MANUAL FOR PROPER
SERVICE PROCEDURES.
HYDRAULIC BLADDER ACCUMULATOR
A Hydraulic Bladder Accumulator (Fig. 2) is used
to store brake fluid at high pressure. The pressurized
fluid is used for Anti-Lock operation and for power
assisted normal braking. The accumulator uses an
elastomeric bladder configuration with a nitrogen
pre-charge of about 6,895 kPa (1,000 psi.) With no
brake fluid in the system, the nitrogen gas pre-
charge applies approximately 6,895 kPa (1,000 psi.)
to one side of the diaphragm (Fig. 2) Under normal operation, the Pump/Motor assembly
charges the accumulator to an operating pressure of
between 11,032 and 13,790 kPa (1600 psi to 2,000
psi.) As pressurized brake fluid enters the accumula-
tor, pushing against the opposite side of the dia-
phragm, (Fig. 2) the nitrogen gas is compressed and
increases in pressure.
DUAL FUNCTION PRESSURE SWITCH
The Dual Function Pressure Switch is located on
the bottom of the hydraulic assembly (Fig. 1) and
monitors Accumulator Pressure. The Dual Function
Pressure Switch, if found to be functioning improp-
erly using the ABS diagnostics, can be replaced. See
service procedure in Electronic Components area of
On Car ABS Service in this section of the service
manual. The primary function is to control operation
of the Pump/Motor assembly and thus maintain
proper accumulator operating pressure. When accu-
mulator pressure falls to or below 11,032 kPa (1600 psi.) the pump motor switch (internal to the dual
function pressure switch) will close. This provides a
ground, through Pin 1 of the Transducer and Switch,
10 way electrical connector to the Pump/Motor relay
coil. The energized coil pulls the relay contacts
closed, providing battery voltage to run the Pump/
Motor. When Accumulator Pressure reaches 13,790
kPa (2,000 psi.) the switch opens, de-energizing the
Pump/Motor Relay that turns off the Pump/Motor. NOTE: THE (CAB) DOES NOT REGULATE
OR CONTROL ACCUMULATOR PRESSURE. The second purpose of the Dual Function Pressure
Switch is to provide a signal to the (CAB) when the
Accumulator Pressure falls below 6,895 kPa (1,000
psi). A Warning Pressure Switch, internal to the
Dual Function Pressure Switch, is normally closed
above 6,895 kPa (1,000 psi.) This sends a ground sig-
nal to pin 17 at the (CAB). At or below 6,895 kPa
(1,000 psi.) the Warning Pressure Switch opens. In-
ternally, the (CAB) (pin 17) detects 12 volts and thus
low pressure. At this warning pressure, the (CAB)
will disable the Anti-Lock Braking functions, light
the Red Brake Warning Lamp and the Amber Anti-
Lock Warning Lamp. After two minutes of continu-
ous detection, a low accumulator fault is stored. Grounding for the Dual Function Pressure Switch.
Is provided through Pin 1 of the Transducer and
Switch, 10 way electrical connector and the Modula-
tor Assembly.
PRESSURE TRANSDUCERS
Two Pressure Transducers are used for brake sys-
tem fault detection. Both transducers generate a
voltage signal (between 0.25 volts and 5.0 volts) that
is proportional to pressure. These signals are com-
Fig. 2 Hydraulic Fluid Accumulator
Ä ANTI-LOCK 10 BRAKE SYSTEM 5 - 77

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