• vacuum booster
• master cylinder
• ABS integrated electronic control module/
hydraulic control unit (HCU), 1 pump motor.
• 4 wheel speed sensor/tone wheel assemblies
• ABS warning indicator
• fuses and wiring harness
• fluid reservoir
• brake lamp switch
ABS With Traction Control
• CAB with Traction Control programming
• HCU with four additional control valves.
• TCS Switch
• TCS indicator
3.3.1 ABS AND BRAKE WARNING
INDICATORS
The amber ABS warning indicator is located in
the instrument cluster. It is used to inform the
driver that the antilock function has been turned
off. The ABS warning indicator is controlled by the
CAB. The CAB controls the lamp with a command
over the PCI bus.
TheABS Warning Indicator will remain litduring
every key cycle until a circuit or component fault is
repaired and the CAB no longer detects the fault.
After repair of a sensor signal fault or a pump motor
fault, the CAB must sense all four wheels at 25
km/h (15 mph) before it will extinguishtheABS and
TCS Indicator.
The Instrument Cluster will illuminate the ABS
Warning Indicator if it loses communication with
the CAB.
The red BRAKE warning indicator is also located
in the instrument cluster. It can be activated in
several ways. Application of the parking brake or a
low fluid signalfromthe fluid level switch located in
the master cylinder reservoir will cause the indica-
tor to come on.
3.3.2 CONTROLLER ANTILOCK BRAKE
(CAB)
The Controller Antilock Brake (CAB) is a
microprocessor-based device that monitors wheel
speeds and controls the antilock functions. The
CAB contains two microprocessors that receive
identical sensor signals and then independently
process the information. The results are then com-
pared to make sure that they agree. Otherwise, the
CAB will turn off the antilock and turn on the ABS
amber warning indicator.
The primary functions of the CAB are to:
• detect wheel locking tendencies
• control fluid pressure modulation to the brakes
during antilock stop
• monitor the system for proper operation
• manage traction control functions
• provide communication to the DRBIIIt while in
diagnostic mode
• store diagnostic information in non-volatile mem-
ory
The CAB continuously monitors the speed of each
wheel. When a wheel locking tendency is detected,
the CAB will command the appropriate valve to
modulate brake fluid pressure in its hydraulic unit.
Brake pedal position is maintained during an an-
tilock stop by being a closed system. The CAB
continues to control pressure in individual hydrau-
lic circuits until a wheel locking tendency is no
longer present. The CAB turns on the pump motor
during an antilock stop.
The antilock brake system is constantly moni-
tored by the CAB for proper operation. If the CAB
detects a system malfunction, it can disable the
antilock system and turn on the ABS warning
indicator. If the antilock function is disabled, the
system will revert to standard base brake system
operation.
The CAB inputs include the following:
• diagnostic communication
• four wheel speed sensors
• three power feeds: valve, pump, and microproces-
sor
• brake lamp switch
• traction control switch (BCM via PCI Bus)
The CAB outputs include the following:
• ABS warning indicator actuation
• 12 volts power to wheel speed sensors
• valve actuation
• diagnostic communication
• PCI bus communication
• traction control lamp illumination
3.3.3 HYDRAULIC CONTROL UNIT
The hydraulic control unit (HCU) contains the
valve block assembly, and pump/motor assembly.
The HCU is attached to the CAB.
Valve Block Assembly: The valve block assem-
bly contains valves with four inlet valves and four
outlet valves. The inlet valves are spring-loaded in
the open position and the outlet valves are spring
loaded in the closed position. During an antilock
stop, these valves are cycled to maintain the proper
slip ratio for each wheel. If a wheel detects slip, the
inlet valve is closed to prevent and further pressure
increase. Then the outlet valve is opened to release
2
GENERAL INFORMATION
ProCarManuals.com
To Next Page
Loading...
