2002 JEEP GRAND CHEROKEE lock

(3) Install lower shoe to shoe spring/adjuster
spring. Needle nose pliers can be used to connect
spring to each shoe.
(4) Install the upper shoe to shoe spring/return
spring with brake pliers (Fig. 83).
(5) Install rotor and caliper anchor assembly.
(6) Install anchor bolts and tighten to 90-115 N´m
(66-85 ft. lbs.).
(7) Actuate park brake lever to unlock the park
brake system.
(8) Adjust the parking brake shoes (Fig. 82).
(9) Install wheel and tire assembly.
(10) Lower vehicle and verify correct parking
brake operation.
ADJUSTMENTS - PARKING BRAKE SHOE
(1) Remove wheel and tire assemblies.
(2) Secure rotor with two wheel nuts.
(3) Remove rubber access plug from back of splash
shield.
(4) Insert brake tool through access hole in splash
shield (Fig. 86). Position tool at bottom of star wheel.
(5) Rotate star wheel upward direction to expand
shoes (while facing front of vehicle).
(6) Expand shoes until light drag is experienced.
Then back off adjuster screw only enough to elimi-
nate drag.
(7) Install plug in splash shield access hole.
(8) Install wheel and tire assemblies.
Fig. 83 Lower Spring
1 - REAR SHOE
2 - NEEDLENOSE PLIERS
3 - ADJUSTER SCREW
4 - LOWER SPRING
Fig. 84 Upper Spring
1 - BRAKE PLIERS
2 - REAR SHOE
3 - UPPER SPRING
Fig. 85 Hold-Down Clip And Pin
1 - HOLD-DOWN CLIP
2 - HOLD-DOWN PIN
Fig. 86 Park Brake Shoe Adjustment
1 - ACCESS HOLE
2 - BRAKE ADJUSTING TOOL
3 - SPLASH SHIELD
5 - 40 BRAKES - BASEWJ
SHOES (Continued)

BRAKES - ABS
TABLE OF CONTENTS
page page
BRAKES - ABS
DESCRIPTION.........................41
OPERATION...........................41
DIAGNOSIS AND TESTING - ANTILOCK
BRAKES............................42
STANDARD PROCEDURE - BLEEDING ABS
BRAKE SYSTEM......................42
SPECIFICATIONS
TORQUE CHART......................42
ELECTRIC BRAKE
DESCRIPTION.........................43
OPERATION...........................43
FRONT WHEEL SPEED SENSOR
DESCRIPTION.........................43
OPERATION...........................43
REMOVAL.............................43INSTALLATION.........................43
G-SWITCH
DESCRIPTION.........................44
OPERATION...........................44
REMOVAL.............................44
INSTALLATION.........................44
REAR WHEEL SPEED SENSOR
DESCRIPTION.........................45
OPERATION...........................45
REMOVAL.............................45
INSTALLATION.........................46
HCU (HYDRAULIC CONTROL UNIT)
DESCRIPTION.........................46
OPERATION...........................46
REMOVAL.............................47
INSTALLATION.........................47
BRAKES - ABS
DESCRIPTION
The purpose of the antilock system is to prevent
wheel lockup during periods of high wheel slip. Pre-
venting lockup helps maintain vehicle braking action
and steering control.
The hydraulic system is a three channel design.
The front brakes are controlled individually and the
rear brakes in tandem.
The ABS electrical system is separate from other
vehicle electrical circuits. A separate controller oper-
ates the system.
OPERATION
The antilock CAB activates the system whenever
sensor signals indicate periods of high wheel slip.
High wheel slip can be described as the point where
wheel rotation begins approaching 20 to 30 percent of
actual vehicle speed during braking. Periods of high
wheel slip occur when brake stops involve high pedal
pressure and rate of vehicle deceleration.
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.
The static check occurs after the ignition switch is
turned to Run position. The dynamic check occurs
when vehicle road speed reaches approximately 30kph (18 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.
ANTILOCK BRAKING
The antilock system prevents lockup during high
slip conditions by modulating fluid apply pressure to
the wheel brake units.
Brake fluid apply pressure is modulated according
to wheel speed, degree of slip and rate of decelera-
tion. A sensor at each wheel converts wheel speed
into electrical signals. These signals are transmitted
to the CAB for processing and determination of
wheel slip and deceleration rate.
The ABS system has three fluid pressure control
channels. The front brakes are controlled separately
and the rear brakes in tandem. A speed sensor input
signal indicating a high slip condition activates the
CAB antilock program.
Two solenoid valves are used in each antilock con-
trol channel. The valves are all located within the
HCU valve body and work in pairs to either increase,
hold, or decrease apply pressure as needed in the
individual control channels.
The solenoid valves are not static during antilock
braking. They are cycled continuously to modulate
pressure. Solenoid cycle time in antilock mode can be
measured in milliseconds.
WJBRAKES - ABS 5 - 41

DIAGNOSIS AND TESTING - ANTILOCK
BRAKES
The ABS brake system performs several self-tests
every time the ignition switch is turned on and the
vehicle is driven. The CAB monitors the systems
input and output circuits to verify the system is oper-
ating correctly. If the on board diagnostic system
senses that a circuit is malfunctioning the system
will set a trouble code in its memory.
NOTE: An audible noise may be heard during the
self-test. This noise should be considered normal.
NOTE: The MDS or DRB III scan tool is used to
diagnose the ABS system. For additional informa-
tion refer to the Electrical section. For test proce-
dures refer to the Chassis Diagnostic Manual.
STANDARD PROCEDURE - BLEEDING ABS
BRAKE SYSTEM
ABS system bleeding requires conventional bleed-
ing methods plus use of the DRB scan tool. The pro-cedure involves performing a base brake bleeding,
followed by use of the scan tool to cycle and bleed the
HCU pump and solenoids. A second base brake bleed-
ing procedure is then required to remove any air
remaining in the system.
(1) Perform base brake bleeding. (Refer to 5 -
BRAKES - STANDARD PROCEDURE) OR (Refer to
5 - BRAKES - STANDARD PROCEDURE).
(2) Connect scan tool to the Data Link Connector.
(3) Select ANTILOCK BRAKES, followed by MIS-
CELLANEOUS, then ABS BRAKES. Follow the
instructions displayed. When scan tool displays TEST
COMPLETE, disconnect scan tool and proceed.
(4) Perform base brake bleeding a second time.
(Refer to 5 - BRAKES - STANDARD PROCEDURE)
OR (Refer to 5 - BRAKES - STANDARD PROCE-
DURE).
(5) Top off master cylinder fluid level and verify
proper brake operation before moving vehicle.
SPECIFICATIONS
TORQUE CHART
TORQUE SPECIFICATIONS
DESCRIPTION N´m Ft. Lbs. In. Lbs.
G-Sensor Bolt 5.6 Ð 50
Hydraulic Control Unit/Controller
Antilock Brakes
Mounting Bolts12 9 125
Hydraulic Control Unit/Controller
Antilock Brakes
Brake Lines16 Ð 144
Hydraulic Control Unit/Controller
Antilock Brakes
CAB Screws1.8 Ð 16
Wheel Speed Sensors
Front Sensor Bolt12-14 106-124 Ð
Wheel Speed Sensors
Rear Sensor Bolt12-14 106-124 Ð
5 - 42 BRAKES - ABSWJ
BRAKES - ABS (Continued)

ELECTRIC BRAKE
DESCRIPTION
The electronic brake distribution (EBD) functions
like a rear proportioning valve. The EBD system uses
the ABS system to control the slip of the rear wheels
in partial braking range. The braking force of the
rear wheels is controlled electronically by using the
inlet and outlet valves located in the HCU.
OPERATION
Upon entry into EBD the inlet valve for the rear
brake circuit is switched on so that the fluid supply
from the master cylinder is shut off. In order to
decrease the rear brake pressure the outlet valve for
the rear brake circuit is pulsed. This allows fluid to
enter the low pressure accumulator (LPA) in the
HCU resulting in a drop in fluid pressure to the rear
brakes. In order to increase the rear brake pressure
the outlet valve is switched off and the inlet valve is
pulsed. This increases the pressure to the rear
brakes. This will continue until the required slip dif-
ference is obtained. At the end of EBD braking (no
brake application) the fluid in the LPA drains back to
the master cylinder by switching on the outlet valve
and draining through the inlet valve check valve. At
the same time the inlet valve is switched on to pre-
vent a hydraulic short circiut in case of another
brake application.
The EBD will remain functional during many ABS
fault modes. If the red and amber warning lamps are
illuminated the EBD may have a fault.
FRONT WHEEL SPEED
SENSOR
DESCRIPTION
A wheel speed sensor is used at each wheel. The
front sensors are mounted to the steering knuckles.
The rear sensors are mounted at the outboard end of
the axle. Tone wheels are mounted to the outboard
ends of the front and rear axle shafts. The gear type
tone wheel serves as the trigger mechanism for each
sensor.
OPERATION
The sensors convert wheel speed into a small digi-
tal signal. The CAB sends 12 volts to the sensors.
The sensor has an internal magneto resistance
bridge that alters the voltage and amperage of the
signal circuit. This voltage and amperage is changed
by magnetic induction when the toothed tone wheel
passes the wheel speed sensor. This digital signal issent to the CAB. The CAB measures the voltage and
amperage of the digital signal for each wheel.
REMOVAL
(1) Raise and support the vehicle.
(2) Remove the front wheel sensor mounting bolt
(Fig. 1).
(3) Remove the sensor from the steering knuckle.
(4) Disengage the sensor wire from the brackets
(Fig. 1)on the steering knuckle.
(5) Disconnect the sensor from the sensor harness
(Fig. 2)and (Fig. 3).
(6) Remove the sensor and wire.
INSTALLATION
(1) Install the sensor on the steering knuckle.
(2) Apply Mopar Lock N' Seal or Loctitet242 to
the sensor mounting bolt. Use new sensor bolt if orig-
inal bolt is worn or damaged.
(3) Install the sensor mounting bolt and tighten
bolt to 12-14 N´m (106-124 in. lbs.).
(4) Engage the grommets on the sensor wire to the
steering knuckle brackets.
(5) Connect the sensor wire to the harness connec-
tor.
(6) Check the sensor wire routing. Be sure the
wire is clear of all chassis components and is not
twisted or kinked at any spot.
(7) Remove the support and lower vehicle.
Fig. 1 Sensor Location
1 - BRACKET
2 - BRACKET
3 - WHEEL SPEED SENSOR
4 - MOUNTING BOLT
WJBRAKES - ABS 5 - 43

INSTALLATION
(1) Insert the sensor through the backing plate
(Fig. 9).
(2) Apply Mopar Lock N' Seal or Loctite 242tto
the original sensor bolt. Use a new bolt if the original
is worn or damaged.
(3) Tighten the sensor bolt to 12-14 N´m (106-124
in. lbs.).
(4) Secure the sensor wire in the brackets and the
retainers on the rear brake lines. Verify that the sen-
sor wire is secure and clear of the rotating compo-
nents.
(5) Route the sensor wires to the rear seat area.
(6) Feed the sensor wires the through floorpan
access hole and seat the sensor grommets into the
floorpan.
(7) Remove the support and lower the vehicle.(8) Fold the rear seat and carpet forward for
access to the sensor wires and connectors.
(9) Connect the sensor wires to the harness con-
nectors.
(10) Reposition the carpet and fold the rear seat
down.
HCU (HYDRAULIC CONTROL
UNIT)
DESCRIPTION
The HCU consists of a valve body, pump motor,
and wire harness.
OPERATION
Accumulators in the valve body store extra fluid
released to the system for ABS mode operation. The
pump is used to clear the accumulator of brake fluid
and is operated by a DC type motor. The motor is
controlled by the CAB.
The valves modulate brake pressure during
antilock braking and are controlled by the CAB.
The HCU provides three channel pressure control
to the front and rear brakes. One channel controls
the rear wheel brakes in tandem. The two remaining
channels control the front wheel brakes individually.
During antilock braking, the solenoid valves are
opened and closed as needed. The valves are not
static. They are cycled rapidly and continuously to
modulate pressure and control wheel slip and decel-
eration.
During normal braking, the HCU solenoid valves
and pump are not activated. The master cylinder and
power booster operate the same as a vehicle without
an ABS brake system.
During antilock braking, solenoid valve pressure
modulation occurs in three stages, pressure increase,
pressure hold, and pressure decrease. The valves are
all contained in the valve body portion of the HCU.
PRESSURE DECREASE
The outlet valve is opened and the inlet valve is
closed during the pressure decrease cycle.
A pressure decrease cycle is initiated when speed
sensor signals indicate high wheel slip at one or
more wheels. At this point, the CAB closes the inlet
then opens the outlet valve, which also opens the
return circuit to the accumulators. Fluid pressure is
allowed to bleed off (decrease) as needed to prevent
wheel lock.
Once the period of high wheel slip has ended, the
CAB closes the outlet valve and begins a pressure
increase or hold cycle as needed.
Fig. 8 Sensor Mounting Bolt
1 - WHEEL SPEED SENSOR
2 - MOUNTING BOLT
Fig. 9 Wheel Speed Sensor
1 - WHEEL SPEED SENSOR
2 - BACKING PLATE
5 - 46 BRAKES - ABSWJ
REAR WHEEL SPEED SENSOR (Continued)

replacement is necessary, replace with the original
Mopartequipment spring type clamp.
CAUTION: A number or letter is stamped into the
tongue of constant tension clamps. If replacement
is necessary, use only a original equipment clamp
with matching number or letter (Fig. 4).
OPERATION
OPERATIONÐCOOLING SYSTEM
The cooling system regulates engine operating tem-
perature. It allows the engine to reach normal oper-
ating temperature as quickly as possible. It alsomaintains normal operating temperature and pre-
vents overheating.
The cooling system also provides a means of heat-
ing the passenger compartment and cooling the auto-
matic transmission fluid (if equipped). The cooling
system is pressurized and uses a centrifugal water
pump to circulate coolant throughout the system.
OPERATIONÐHOSE CLAMPS
The worm type hose clamp uses a specified torque
value to maintain proper tension on a hose connec-
tion.
Fig. 1 Engine Cooling System 4.7L Engine
1 - LH CYL. HEAD
2 - AIR BLEED
3 - THERMOSTAT LOCATION
4 - RH CYL. HEAD5 - RH BANK CYL. BLOCK
6 - LH BANK CYL. BLOCK
7 - COOLANT TEMP. SENSOR
7 - 2 COOLINGWJ
COOLING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
6. Poor seals at the radiator cap. 6. (a) Check condition of cap and cap seals.
(Refer to 7 - COOLING/ENGINE/RADIATOR
PRESSURE CAP - DIAGNOSIS AND
TESTING).
(b) Check condition of radiator filler
neck. If neck is bent or damaged,
replace radiator.
7. Coolant level low in radiator but
not in coolant reserve/overflow tank.
This means the radiator is not
drawing coolant from the coolant
reserve/overflow tank as the engine
cools7. (a) Check condition of radiator cap and
cap seals. (Refer to 7 - COOLING/ENGINE/
RADIATOR PRESSURE CAP - DIAGNOSIS
AND TESTING).
(b) Check condition of radiator filler neck. If
neck is bent or damaged, replace radiator.
(c) Check condition of the hose from the
radiator to the coolant tank. It should fit tight
at both ends without any kinks or tears.
Replace hose if necessary.
(d) Check coolant reserve/overflow tank and
tanks hoses for blockage. Repair as
necessary.
8. Incorrect coolant concentration 8. Check coolant. (Refer to 7 - COOLING/
ENGINE/COOLANT - DESCRIPTION) for
correct coolant/water mixture ratio.
9. Coolant not flowing through
system9. Check for coolant flow at radiator filler
neck with some coolant removed, engine
warm and thermostat open. Coolant should
be observed flowing through radiator. If flow
is not observed, determine area of
obstruction and repair as necessary.
10. Radiator or A/C condenser fins
are dirty or clogged.10. Remove insects and debris. (Refer to 7 -
COOLING/ENGINE/RADIATOR -
CLEANING).
11. Radiator core is corroded or
plugged.11. Have radiator re-cored or replaced.
12. Aftermarket A/C installed without
proper radiator.12. Install proper radiator.
13. Fuel or ignition system
problems.13. Refer to FUEL and /or IGNITION
CONTROL for diagnosis.
14. Dragging brakes. 14. Check and correct as necessary. (Refer
to 5 - BRAKES - DIAGNOSIS AND
TESTING) for correct procedures.
15. Bug screen or cardboard is
being used, reducing airflow.15. Remove bug screen or cardboard.
16. Thermostat partially or
completely shut.16. Check thermostat operation and replaces
necessary. (Refer to 7 - COOLING/ENGINE/
ENGINE COOLANT THERMOSTAT -
DIAGNOSIS AND TESTING).
7 - 6 COOLINGWJ
COOLING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
7. Water pump impeller loose on
shaft.7. Check water pump and replace as
necessary. (Refer to 7 - COOLING/ENGINE/
WATER PUMP - DIAGNOSIS AND
TESTING).
8. Loose accessory drive belt. (water
pump slipping)8. (Refer to 7 - COOLING/ACCESSORY
DRIVE/DRIVE BELTS - DIAGNOSIS AND
TESTING). Check and correct as necessary.
9. Air leak on the suction side of the
water pump allows air to build up in
cooling system causing thermostat
to open late.9. Locate leak and repair as necessary.
PRESSURE CAP IS
BLOWING OFF STEAM
AND/OR COOLANT TO
COOLANT TANK.
TEMPERATURE GAUGE
READING MAY BE
ABOVE NORMAL BUT
NOT HIGH. COOLANT
LEVEL MAY BE HIGH IN
COOLANT RESERVE/
OVERFLOW TANK1. Pressure relief valve in radiator
cap is defective.1. Check condition of radiator cap and cap
seals. (Refer to 7 - COOLING/ENGINE/
RADIATOR PRESSURE CAP - DIAGNOSIS
AND TESTING). Replace cap as necessary.
COOLANT LOSS TO THE
GROUND WITHOUT
PRESSURE CAP
BLOWOFF. GAUGE
READING HIGH OR HOT1. Coolant leaks in radiator, cooling
system hoses, water pump or
engine.1. Pressure test and repair as necessary.
(Refer to 7 - COOLING - DIAGNOSIS AND
TESTING).
DETONATION OR
PRE-IGNITION (NOT
CAUSED BY IGNITION
SYSTEM). GAUGE MAY
OR MAY NOT BE
READING HIGH1. Engine overheating. 1. Check reason for overheating and repair
as necessary.
2. Freeze point of coolant not
correct. Mixture is too rich or too
lean.2. Check coolant concentration. (Refer to 7 -
COOLING/ENGINE/COOLANT -
DESCRIPTION) and adjust ratio as required.
HOSE OR HOSES
COLLAPSE WHILE
ENGINE IS RUNNING1. Vacuum created in cooling system
on engine cool-down is not being
relieved through coolant reserve/
overflow system.1. (a) Radiator cap relief valve stuck. (Refer
to 7 - COOLING/ENGINE/RADIATOR
PRESSURE CAP - DIAGNOSIS AND
TESTING). Replace if necessary
(b) Hose between coolant reserve/overflow
tank and radiator is kinked. Repair as
necessary.
(c) Vent at coolant reserve/overflow tank is
plugged. Clean vent and repair as necessary.
(d) Reserve/overflow tank is internally
blocked or plugged. Check for blockage and
repair as necessary.
7 - 8 COOLINGWJ
COOLING (Continued)