Antilock Brakes - Jeep 1997 Grand Cherokee Service Manual

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GENERAL INFORMATION
ANTILOCK BRAKE SYSTEM
DESCRIPTION AND OPERATION
ABS SYSTEM RELAYS
ABS WARNING LAMP . . . . . . . . . . . . . . . . . . . 38
ACCELERATION SWITCH . . . . . . . . . . . . . . . . 38
ANTILOCK BRAKE SYSTEM
COMBINATION VALVE . . . . . . . . . . . . . . . . . . . 37
CONTROLLER ANTILOCK BRAKES . . . . . . . . . 36
HYDRAULIC CONTROL UNIT . . . . . . . . . . . . . . 36
WHEEL SPEED SENSORS AND TONE WHEEL . .
DIAGNOSIS AND TESTING

ANTILOCK BRAKES . . . . . . . . . . . . . . . . . . . . . 38

GENERAL INFORMATION
ANTILOCK BRAKE SYSTEM
The antilock brake system (ABS) is an electroni-
cally operated, all wheel brake control system.
The system is designed to prevent wheel lockup
and maintain steering control during periods of high
wheel slip when braking. Preventing lockup is accom-
plished by modulating fluid pressure to the wheel
brake units.
The hydraulic system is a three channel design.
The front wheel brakes are controlled individually
and the rear wheel brakes in tandem (Fig. 1). The
ABS electrical system is separate from other electri-
cal circuits in the vehicle. A specially programmed
controller antilock brake unit operates the system
components.
ABS system major components include:
• Controller Antilock Brakes (CAB)
• Hydraulic Control Unit (HCU)
• Wheel Speed Sensors (WSS)
• Acceleration Switch
• ABS Warning Light
DESCRIPTION AND OPERATION
ANTILOCK BRAKE SYSTEM
Battery voltage is supplied to the CAB ignition ter-
minal when the ignition switch is turned to Run posi-
tion. The CAB performs a system initialization
procedure at this point. Initialization consists of a
static and dynamic self check of system electrical
components.
ANTILOCK BRAKES
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HYDRAULIC BRAKE LINES WIRES TO WHEEL SPEED MASTER POWER BRAKE BOOSTER ACCELERATION SWITCH RIGHT FRONT WHEEL COMBINATION VALVE LEFT FRONT WHEEL RIGHT REAR WHEEL LEFT REAR WHEEL CYLINDER HCU HARNESS TO WHEELS RESERVOIR SENSORS
INDEX
SERVICE PROCEDURES
BLEEDING ABS BRAKE SYSTEM
REMOVAL AND INSTALLATION
ACCELERATION SWITCH . . . . . . . . . . . . . . . . 40
FRONT WHEEL SPEED SENSOR
HYDRAULIC CONTROL UNIT/CONTROLLER
ANTILOCK BRAKES . . . . . . . . . . . . . . . . . . . 38
REAR WHEEL SPEED SENSOR
DISASSEMBLY AND ASSEMBLY
HYDRAULIC CONTROL UNIT/CONTROLLER
ANTILOCK BRAKE . . . . . . . . . . . . . . . . . . . . 41
37 SPECIFICATIONS
TORQUE CHART . . . . . . . . . . . . . . . . . . . . . . . 42
Fig. 1 Antilock Brake System
The static check occurs after the ignition switch is
turned to Run position. The dynamic check occurs
when vehicle road speed reaches approximately 10
kph (6 mph). During the dynamic check, the CAB
briefly cycles the pump and solenoids to verify oper-
ation.
If an ABS component exhibits a fault during ini-
tialization, the CAB illuminates the amber warning
light and registers a fault code in the microprocessor
memory.
NORMAL BRAKING
The CAB monitors wheel speed sensor inputs con-
tinuously while the vehicle is in motion. However,
HCU AND CAB
BRAKES
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5 - 35
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