Chrysler PT Cruiser 2001 Service Manual Supplement page 1960

3.1.4 SYSTEM COMPONENTS
ANTILOCK BRAKE SYSTEM
•
Integrated Controller Unit (ICU)
mounting bracket
controller antilock brake (CAB)
hydraulic control unit (HCU)pump/motor as-
sembly:
1 motor
2 pumps
valve block assembly: 10 valves/solenoids (4
• vacuum booster
• master cylinder (w/center valves and fluid reser-
voir)
•
4 wheel speed sensor/tone wheel assemblies
• ABS warning indicator (cluster)
• Trac off indicator (cluster)
•
fuses and wiring harness (w/trac on/off switch)
3.1.5 ABS AND RED BRAKE WARNING
INDICATOR
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
due to a system malfunction. The CAB controls the
lamp indirectly. The CAB monitors its own func-
tions. If the CAB determines that the ABS indicator
should be on, the CAB sends a message via the PCI
BUS to the instrument cluster and the cluster turns
on the indicator. The instrument cluster sends a
message over the PCI BUS, if the CAB does not
respond the instrument cluster will illuminate the
ABS indicator.
The red brake warning indicator is located in the
instrument cluster. It can be activated by applica-
tion of the parking brake, a leak in the front or rear
wheel brake hydraulic circuit which causes the
master cylinder reservoir to be low on fluid, or by
turning the ignition switch to the start position.
The red brake warning indicator can also be turned
on if the CAB indicates an EBD failure.
inlet valves, 4 outlet
valves, 2 traction con-
trol valves.).
2 hydraulic shuttle
valves
2 accumulators
GENERAL INFORMATION
3.1.4 CONTROLLER ANTILOCK BRAKE
(CAB)
The antilock brake controller (CAB) is a
microprocessor-based device that monitors wheel
speeds and controls the antilock functions.
The primary functions of the CAB are:
•
monitor wheel speeds
•
detect wheel locking tendencies
• detect wheel slip
• control fluid pressure modulation to the brakes
during antilock stop and traction control opera-
tion
• monitor the system for proper operation
• provide communication to the DRBIII while in
diagnostic mode
• store diagnostic information in non-volatile
memory
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 with the use of
3 accumulators. The CAB continues to control pres-
sure in individual hydraulic 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 the proper operation. If the
CAB detects a system malfunction, it can disable
the antilock system and turn on the antilock warn-
ing lamp. If the antilock function is disabled, the
system will revert to standard base brake system
operation.
The CAB inputs include the following:
•
four wheel speed sensors
•
brake lamp switch
• ignition switch
• battery voltage
•
diagnostic communication (PCI BUS)
• traction control switch
The CAB outputs include the following:
• ten valve/solenoid drivers
•
pump/motor actuation
•
ABS warning indicator actuation (PCI BUS)
• red brake warning indicator actuation (PCI BUS)
• Trac off lamp (PCI BUS)
•
Trac lamp (PCI BUS)
• diagnostic communication (PCI BUS)
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