1993 CHEVROLET DYNASTY turn signal

GROUP TAB LOCATOR
Introduction
8ABattery/Starting/Charging
Systems Diagnostics
8BBattery/Starter/Generator Service
8COverhead Console
8DIgnition Systems
8EInstrument Panel and Gauges
8FAudio System
8GHorns
8HVehicle Speed Control
8JTurn Signal/Hazard Warning Flasher
8KWindshield Wiper/Washer Systems
8LLamps
8MRestraint Systems
8NRear Window Defogger
8PPower Locks
8QVehicle Theft Security System
8RPower Seats
8SPower Windows
8TPower Mirrors
8UChime Warning/Reminder Systems
14Fuel Systems
25Emission Control Systems
Component and System Index
Service Manual Comment Forms (Rear of Manual)

COMPONENT AND SYSTEM INDEX
Name Group-page Name Group-page
AUDIO SYSTEM ............................ 8F-1
ANTENNAS ............................ 8F-20
COMPACT DISC PLAYER ................... 8F-30
RADIOS ............................... 8F-1
SPEAKERS ............................. 8F-24
BATTERY/STARTER/GENERATOR SERVICE ..........8B-1
BATTERY REMOVAL, INSTALLATION AND SERVICE . . 8B-1
GENERATOR ............................ 8B-9
SPECIFICATIONS ........................ 8B-12
STARTER .............................. 8B-4
BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS ........................... 8A-1
BATTERY TEST PROCEDURES ON-VEHICLE .......8A-3
FAULT CODESÐON BOARD DIAGNOSTICS .......8A-23
GENERAL INFORMATION .................... 8A-1
GENERATOR TEST PROCEDURES ON VEHICLE ....8A-19
IGNITION OFF DRAW (IOD) ..................8A-9
SPECIFICATIONS ........................ 8A-28
STARTER TEST PROCEDURES ON VEHICLE ......8A-11
CHIME WARNING/REMINDER SYSTEM ............8U-1
EMISSION CONTROL SYSTEMS .................25-1
EVAPORATIVE EMISSION CONTROLS ...........25-1
EXHAUST EMISSION CONTROLS ..............25-17
FUEL SYSTEMS ............................ 14-1
2.2L TURBO III MULTI-PORT FUEL INJECTIONÐ GENERAL DIAGNOSIS ................... 14-95
2.2L TURBO III MULTI-PORT FUEL INJECTIONÐ ON-BOARD DIAGNOSTICS ................14-100
2.2L TURBO III MULTI-PORT FUEL INJECTIONÐ SERVICE PROCEDURES .................14-107
2.2L TURBO III MULTI-PORT FUEL INJECTIONÐ SYSTEM OPERATION .................... 14-83
2.2L/2.5L SINGLE POINT FUEL INJECTIONÐ GENERAL DIAGNOSIS ................... 14-35
2.2L/2.5L SINGLE POINT FUEL INJECTIONÐ ON-BOARD DIAGNOSTICS .................14-41
2.2L/2.5L SINGLE POINT FUEL INJECTIONÐ SERVICE PROCEDURES .................. 14-48
2.2L/2.5L SINGLE POINT FUEL INJECTIONÐ SYSTEM OPERATION .................... 14-24
2.5L FLEXIBLE FUEL MULTI-PORT FUEL INJECTIONÐGENERAL DIAGNOSIS ..........14-66
2.5L FLEXIBLE FUEL MULTI-PORT FUEL INJECTIONÐON-BOARD DIAGNOSTICS ........14-70
2.5L FLEXIBLE FUEL MULTI-PORT FUEL INJECTIONÐSERVICE PROCEDURES .........14-77
2.5L FLEXIBLE FUEL MULTI-PORT FUEL INJECTIONÐSYSTEM OPERATION ...........14-55
3.0L MULTI-PORT FUEL INJECTIONÐGENERAL DIAGNOSIS .......................... 14-125
3.0L MULTI-PORT FUEL INJECTIONÐON-BOARD DIAGNOSTICS ........................ 14-130
3.0L MULTI-PORT FUEL INJECTIONÐSERVICE PROCEDURES ........................ 14-138
3.0L MULTI-PORT FUEL INJECTIONÐSYSTEM OPERATION ......................... 14-113
3.3L AND 3.8L MULTI-PORT FUEL INJECTIONÐ GENERAL DIAGNOSIS ................... 14-157 3.3L AND 3.8L MULTI-PORT FUEL INJECTIONÐ
ON-BOARD DIAGNOSTICS ................14-162
3.3L AND 3.8L MULTI-PORT FUEL INJECTIONÐ SERVICE PROCEDURES .................14-169
3.3L AND 3.8L MULTI-PORT FUEL INJECTIONÐ SYSTEM OPERATION ................... 14-145
ACCELERATOR PEDAL AND THROTTLE CABLE ....14-21
FUEL DELIVERY SYSTEM .................... 14-3
FUEL TANKS ........................... 14-14
GENERAL INFORMATION .................... 14-1
SPECIFICATIONS ........................ 14-178
HORNS ................................. 8G-1
IGNITION SYSTEMS ......................... 8D-1
2.2L TBI, 2.5L TBI, 2.5L MPI AND 3.0L IGNITION SYSTEMSÐDIAGNOSTIC PROCEDURES .......8D-11
2.2L TBI, 2.5L TBI, 2.5L MPI AND 3.0L IGNITION SYSTEMSÐSERVICE PROCEDURES ..........8D-14
2.2L TBI, 2.5L TBI, 2.5L MPI AND 3.0L IGNITION SYSTEMSÐSYSTEM OPERATION ............8D-1
2.2L TURBO III, 3.3L AND 3.8L IGNITION SYSTEMÐDIAGNOSTIC PROCEDURES ........8D-35
2.2L TURBO III, 3.3L AND 3.8L IGNITION SYSTEMÐSYSTEM OPERATION ............8D-24
2.2L TURBO III, 3.3L AND 3.8L IGNITION SYSTEMSÐSERVICE PROCEDURES ..........8D-39
IGNITION SWITCH ....................... 8D-45
SPECIFICATIONS ........................ 8D-47
INSTRUMENT PANEL AND GAUGES ...............8E-1
AA BODY .............................. 8E-1
AC AND AY BODIES ...................... 8E-23
AG AND AJ BODIES ...................... 8E-42
AP BODY ............................. 8E-58
LAMPS .................................. 8L-1
BULB APPLICATION TABLE ..................8L-38
CONCEALED HEADLAMPS ..................8L-27
EXTERIOR LAMP SWITCHES AND HEADLAMP ALIGNMENT ........................... 8L-3
EXTERIOR LAMP SYSTEMS .................8L-25
EXTERIOR LAMPSÐAA BODY ................8L-7
EXTERIOR LAMPSÐAC BODY ...............8L-10
EXTERIOR LAMPSÐAG BODY ...............8L-14
EXTERIOR LAMPSÐAJ BODY ................8L-16
EXTERIOR LAMPSÐAP BODY ...............8L-19
EXTERIOR LAMPSÐAY-BODY ................8L-22
GENERAL INFORMATION .................... 8L-1
ILLUMINATED ENTRY SYSTEM ...............8L-33
OVERHEAD CONSOLE ........................ 8C-1
AA BODY .............................. 8C-1
AC AND AY BODY ........................ 8C-6
AG AND AJ BODIES ...................... 8C-13
AP BODY ............................. 8C-21
POWER LOCKS ............................ 8P-1
POWER MIRRORS ..........................8T-1
POWER SEATS ............................ 8R-1
POWER WINDOWS .......................... 8S-1
REAR WINDOW DEFOGGER .................... 8N-1
RESTRAINT SYSTEMS ....................... 8M-1
TURN SIGNALS AND HAZARD WARNING FLASHER ....8J-1
VEHICLE SPEED CONTROL .................... 8H-1

In addition, there is an air regeneration cycle that
is controlled by the Control Module (CM). If the
height sensor signal is in the neutral or high posi-
tion. When the ignition switch is turned to the ON
position, after a 22 to 28 second delay, the compres-
sor will run from 2 to 6 seconds. To prevent excessive cycling between the compres-
sor and the exhaust solenoid circuits during normal
ride conditions. A 12 to 18 second delay is incorpo-
rated in the microprocessor.
HEIGHT SENSOR
A magnetic switch type sensor, located in the right
air shock absorber, monitors rear vehicle height. The
sensor sends signals to the (CM) relating to vehicle
rear suspension status (low, trim, high).
AIR LINES AND FITTINGS
To release an air supply line from a rear shock ab-
sorber assembly. Push in (toward shock absorber) on
the plastic ring of the shock absorber air line fitting.
Then while holding in the plastic ring on shock ab-
sorber fitting pull the air supply line strait out of fit-
ting (Fig. 3). The fitting has a unique push-in feature. A brass
type collet locks the air line in place. One rubber
O-ring seals the air line to prevent air leakage. To
attach air line, push into fitting (Fig. 4).
COMPRESSOR RELAY
The relay is mounted to a bracket on the Control
Module (CM). When the relay is energized, it allows
the compressor to operate. This unit is controlled by
the CM.
AIR ADJUSTABLE SHOCK ABSORBERS
Air shock absorbers are essentially hydraulic shock
absorbers with a neoprene bladder sealing upper and
lower sections together. This creates an air cylinder
inside of the shock absorber.
AIR DRYER
The air dryer is attached to the compressor. This
component serves two purposes; it absorbs moisture
from the atmosphere before it enters the system. And
with the internal valves maintains a residual system
pressure of 69 to 152 kPa (10 to 22 psi).
AIR CHECK, RESIDUAL (FIG. 5).
The air dryer has a valves arrangement that main-
tains 69 to 152 kPa (10 to 22 psi) in the air shocks.
This is to improve the ride characteristics of the ve-
hicle under light load conditions. To test this func-
tion, perform the following procedure: (1) Remove the air line from the dryer and right
shock absorber. Attach a piece of bulk nylon tubing
to one side of a Pressure Gauge (0-300 psi), and to
the right shock absorber (Fig. 5). (2) Attach another piece of nylon tubing from the
dryer (compressor) to other side of the pressure
gauge.
Fig. 2 Compressor AssemblyFig. 3 Release Air Line from Fitting
Fig. 4 Push Air Line into Fitting
2 - 60 SUSPENSION AND DRIVESHAFTS Ä

(3) Check solenoid to volume canister joint.
² Front strut to solenoid valve connection.
² Rear spring to solenoid valve connection.
(4) Check air line for ruptures, cuts, splits or heat
damage. Use a soap and water solution or a liquid de-
veloped for leak detection.
SYSTEM OPERATION
ENGINE RUN OPERATION
The system will compensate for load
addition/removal when.
² The trunk and all doors are closed.
² The engine speed exceeds 600 R.P.M.
² Throttle angle is less than 65 degrees.
² The brake is not applied.
² You are not cornering above 10 mph.
² There is not a charging system problem with the
vehicle.
ENGINE OFF OPERATION
After passengers/load is removed from the vehicle
the system will correct the vehicle attitude after:
² The trunk and all doors are closed.
² The ignition switch is in the OFF position.
Opening the a door or trunk wakes up the body
computer and the air suspension module. The air
suspension system is now capable of leveling, if
required.
LONG TERM IGNITION OFF OPERATION
The system is capable of one an additional leveling
cycle. After 2 continuous hours of ignition key off and
no door open or trunk open activities. This feature is
implemented to eliminate possible ice freeze-up be-
tween the tire and the inner fender shield.
SYSTEM OPERATION INHIBITORS
The air suspension system is inhibited when:
² The trunk is open.
² A door(s) is/are open.
² The brake pedal is engaged.
² The throttle is at the wide open position.
² The charging system fails.
The maximum compressor pump or exhaust
time is 3 minutes.
SYSTEM FAILURES
Vehicles equipped with air suspension and overhead
console. Will alert the driver of an air suspension
system malfunction. A warning Check Air Suspension
will appear on the overhead console screen.
SAFETY CONCERNS
WARNING: REAR AIR SPRINGS MUST BE DEFLATED
BEFORE BEING REMOVED FROM THE VEHICLE.
WARNING: OPEN TRUNK, OR DOOR(S) OR REMOVE
GROUND STRAP FROM BATTERY BEFORE HOIST-
ING OR JACKING A VEHICLE DURING MECHANICAL
REPAIRS.
WARNING: IF THE VEHICLE NEEDS SERVICE OR
REPAIR OF THE REAR SHOCK ABSORBERS OR
REAR AXLE PIVOT BUSHINGS. THE REAR AIR
SPRINGS MUST HAVE THE AIR PRESSURE RE-
MOVED BEFORE THE VEHICLE CAN BE SERVICED
SAFELY.
SHIPPING MODE
(1) Removing shipping height signal for customer
use.
² Use DRB II tester and 1991 Chassis (Air Suspen-
sion) service cartridge.
² Follow DRB II requirements to cancel shipping
height message in the body computer.
² Connect the Ignition Off Draw (I.O.D.) circuit.
The connection of the IOD circuit will cancel
the Shipping height signal. (2) Return to shipping height.
² Set shipping command in the body computer using
the DRB II and the 1991 Chassis (Air suspension)
service cartridge.
² Disconnect the I.O.D. connector.
DIAGNOSIS
INITIAL DIAGNOSTIC CHECK
(1) Check for blown or missing fuses.
Fig. 9 Compressor Current Draw Test
2 - 78 SUSPENSION AND DRIVESHAFTS Ä

semblies. This sensor when emitting a sound signals
that brake lining may need inspection and/or re-
placement.
SHOE AND LINING WEAR
If a visual inspection does not adequately deter-
mine the condition of the lining, a physical check
will be necessary. To check the amount of lining
wear, remove the wheel and tire assemblies, and the
calipers. Remove the shoe and lining assemblies. (See Brake
Shoe Removal paragraph). Combined shoe and lining thickness should be
measured at the thinnest part of the assembly. When a shoe and lining assembly is worn to a
thickness of approximately 7.95 mm (5/16 inch) it
should be replaced. Replace bothshoe assemblies (inboard and out-
board) on the front wheels. It is necessary that both
front wheel sets be replaced whenever shoe assem-
blies on either side are replaced. If a shoe assembly does not require replacement.
Reinstall, the shoe assemblies making sure each shoe
assembly is returned to the original position. (See
Brake Shoe Installation).
Fig. 4 Disc Brake Caliper Mounting (Non-Family Caliper)
Fig. 5 Disc Brake Caliper Mounting (Typical)
Fig. 6 Piston Seal Function for Automatic Adjustment
Ä BRAKES 5 - 33

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 has a set of elec-
trical solenoid valves and a hydraulic line to provide
hydraulic modulation. For vehicle stability, though
both rear wheel valves receive the same electrical
signal. The system can build, hold or reduce pressure
at each wheel. Depending on the signals generated
by the wheel speed sensors (WSS) at each wheel and
received at the Controller-Anti-Lock Brake (CAB). The ABS system represents current state-of-the-art
in vehicle braking systems. The ABS system offers the driver increased safety and vehicle control during
hard braking. This is accomplished by a sophisticated
system of electrical and hydraulic components. That
differ from conventional vacuum boosted hydraulic
actuation systems. Because, there are several perfor-
mance characteristics that may at first seem differ-
ent but should be considered normal. These
characteristics are discussed below. More technical
details are discussed further in this section.
PEDAL FEEL
The ABS System uses hydraulic power assist for
both normal power assisted braking and to provide a
source of high pressure hydraulic fluid during Anti-
Lock Braking. In general, pedal feel will be similar
to that of a conventional vacuum boosted brake sys-
tem. If during an Anti-Lock stop additional force is
applied to the brake pedal, or the brake pedal is re-
leased and reapplied rapidly. The driver may notice a
very hard pedal feel. This is due to normal isolation
of the master cylinder during A.B.S. operation as
wheel brake pressure is fed from the hydraulic
booster.
ANTI-LOCK OPERATION
During Anti-Lock Braking, brake pressures are
modulated by cycling electric valves. The cycling of
these valves can be heard as a series of popping or
ticking noises. In addition, the cycling may be felt as
a pulsation in the brake pedal, although no pedal
movement will be noticed. If Anti-Lock operation oc-
curs during hard braking. Some pulsation may be
felt in the vehicle body due to fore and aft movement
of the vehicles suspension as brake pressures are
modulated. Although ABS operation is available at virtually
all vehicle speeds. It will automatically turn off at
speeds below 3 to 5 mph. Therefore wheel lock-up
may be perceived at the very end of an Anti-Lock
stop and should be considered normal.
TIRE NOISE & MARKS
Although the ABS system prevents complete wheel
lock-up, some wheel slip is desired to achieve opti-
mum 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 interpreted as
total wheel lock-up. Complete wheel lock-up normally leaves black tire
marks on dry payment. However, Anti-Lock Braking
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.
Fig. 3 (CAB) Controller Anti-Lock Brake Module
Fig. 4 ABS Pump/Motor Assembly
5 - 74 ANTI-LOCK 10 BRAKE SYSTEM Ä

ABS EQUIPPED 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. Hydroplaning
results in the vehicle tires leaving the road surface
rendering the vehicle almost uncontrollable. In addi-
tion, extreme steering maneuvers at high speed or
high speed cornering beyond limits of tire adhesion
to the road surface may cause vehicle skidding. So,
the ABS system is termed Anti-Lock instead of Anti-
Skid. One of the significant benefits of the ABS system is
that of maintaining steering control during hard
braking or during braking on slippery surfaces. It is
therefore possible to steer the vehicle while braking
on almost any road surface.
ABS SYSTEM SELF-DIAGNOSTICS
The ABS system has been designed with Self Diag-
nostic Capability. There are two self checks the sys-
tems performs every time the vehicle is started.
First, when the key is turned on the system performs
an electrical check called Start-Up Cycle. During this
check, the Red Brake Warning Lamp and the Amber
Anti-Lock Warning Lamp are illuminated. Then
turned off at the end of the test, after about 1 to 2
seconds. When the vehicle reaches a speed of about 3
to 4 miles per hour. The system performs a func-
tional check called Drive-Off. During Drive-Off. hy-
draulic valves are activated briefly to test their
function. Drive-Off can be detected as a series of
rapid clicks upon driving off the first time the car is
started. If the brake pedal is applied during Drive-
Off, the test is by-passed. Both of these conditions
are a normal part of the system self test. Most fault
conditions will set a ABS Fault Code in the (CAB),
which can be retrieved to aid in fault diagnosis. De-
tails can be found in Diagnosis Section.
ABS WARNING SYSTEMS OPERATION
The ABS system uses two methods for notifying
the driver of a system malfunction. These include the
standard Red Brake Warning Lamp and an Amber
Anti-Lock Warning Lamp, both located in the instru-
ment cluster. The purpose of these two lamps are dis-
cussed in detail below.
RED BRAKE WARNING LAMP
The Red Brake Warning Lamp, located in the in-
strument cluster, will Turn On to warn the driver of
brake system conditions that may result in reduced
braking ability. The lamp is also turned on when the
parking brake is not fully released. Conditions which
may cause the Red Brake Warning Lamp to Turn On
include: ²
Parking brake not fully released. If the parking
brake is applied or not fully released. The switch on the
parking brake pedal assembly will ground the Red
Brake Warning Lamp circuit and cause the lamp to
turn on. On vehicles equipped with mechanical instru-
ment clusters, the Amber Anti-Lock Lamp will turn on
if the vehicle is driven above 3 miles per hour with the
Parking Brake applied.
² Low brake fluid. The fluid level sensor in the hy-
draulic assembly reservoir will ground the Red Brake
Warning Lamp circuit if low brake fluid level is de-
tected. In addition, ABS will be deactivated above 3
miles per hour and the Amber Anti-Lock Warning
Lamp will be illuminated. If the vehicle is equipped
with EVIC, a low fluid condition will also cause the
Low Brake Fluid message to appear.
² Low Accumulator Pressure. In the event of low
accumulator pressure, the dual function pressure
switch in the hydraulic assembly will signal the (CAB)
to ground the Red Brake Warning Lamp circuit. This
will cause the Red Brake Warning Lamp to turn on.
Low accumulator pressure also results in the activa-
tion of the Yellow Anti-Lock Warning Lamp. Low accu-
mulator pressure may result in loss of power assist.
² Modulator Or (CAB) Faults. The modulator assem-
bly or (CAB) may turn on the Yellow Anti-Lock Warn-
ing Lamp, if certain faults are detected in either the
modulator assembly or the (CAB).
² Bulb check. As a bulb check, the Red Brake Warning
Lamp will illuminate whenever the ignition switch is
placed in the crank position. Illumination of the red Brake Warning Lamp
may indicate reduced braking ability. A vehicle
that has the Red Brake Warning Lamp ON should
not be driven except to do diagnostic procedures
described in Section 2 of this manual. Most con-
ditions that turn on the Red Brake Warning
Lamp will also turn on the Amber Anti-Lock
Warning Lamp, consequently disabling the Anti-
Lock function.
ANTI-LOCK WARNING LAMP
The Anti-Lock Warning Lamp is located in the in-
strument cluster and is Amber in color. The Amber
Anti-Lock Warning Lamp is illuminated when the
(CAB) detects a condition that results in a shutdown of
Anti-Lock function. The Amber Anti-Lock Warning
Lamp is normally on until the (CAB) completes its self
tests and turns the lamp off. For example, if the (CAB)
is disconnected, the lamp is on. Display of the Amber Anti-Lock Warning Lamp
without the Red Brake Warning Lamp indicates
only that Anti-Lock function has been disabled.
Power assisted normal braking is unaffected.
Ä ANTI-LOCK 10 BRAKE SYSTEM 5 - 75

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