2003 JEEP GRAND CHEROKEE 23 Body

(3) Push the cables into the upper suspension arm
brackets.
(4) Install the cable retainer bolts to the rear
spring pads.
(5) Install the ABS sensor wiring harness to the
rear brake cables.
(6) Install the rotors, caliper anchors and brake
calipers.
(7) Install the wheel and tire assemblies.
(8) Remove support and lower the vehicle.
(9) Engage the cable ends into the parking brake
equalizer.
(10) Pull on the lever to release the lock out
spring.
(11) Install center console, (Refer to 23 - BODY/IN-
TERIOR/FLOOR CONSOLE - INSTALLATION).
(12) Fold down the rear carpet cover and rear seat.
(13) Verify parking brake operation.
LEVER
REMOVAL
(1) Remove center console,(Refer to 23 - BODY/IN-
TERIOR/FLOOR CONSOLE - REMOVAL).
(2) Lift up rear seat and carpet covering the park-
ing brake cables.
(3) Place a screw driver through the front cable
eyelet (Fig. 77) and pry back on the front cable.(4) Have an assistant pry down the lock out spring
through the hole in the side of the park brake lever
(Fig. 78) with a small screw driver. Then slowly
release the front cable.
NOTE: Their should be slack in the cable if the lock
out spring is engaged.
(5) Disconnect parking brake switch wiring con-
nector.
(6) Disengage front cable end from parking brake
lever.
(7) Compress the cable retainer with a 13 mm
wrench (Fig. 79) and remove the cable from the park-
ing brake lever bracket.
Fig. 77 FRONT CABLE
1 - REAR CABLES
2 - FRONT CABLE EYELET
3 - FRONT CABLE
4 - EQUALIZER
Fig. 78 Lock Out Spring
1 - LOCK OUT SPRING
Fig. 79 Parking Brake Lever Bracket
1 - FRONT CABLE
2 - WRENCH
5 - 38 BRAKES - BASEWJ
CABLES (Continued)

(8) Remove the park brake lever mounting nuts
and console bracket (Fig. 80).
(9) Lift the lever assembly off the mounting studs
and pull the front cable out of the lever bracket.
INSTALLATION
(1) Install the lever assembly on the mounting
studs while feeding the front cable into the lever
bracket.
(2) Install the console bracket (Fig. 80) and mount-
ing nuts.
(3) Engage the front cable end to the lever.
(4) Connect parking brake switch wire connector.
(5) Pull on the lever to release the lock out spring.
(6) Install center console,(Refer to 23 - BODY/IN-
TERIOR/FLOOR CONSOLE - INSTALLATION).
(7) Fold down the rear carpet cover and rear seat.
SHOES
REMOVAL
(1) Lock out park brake lever (Fig. 81).
(2) Raise vehicle.
(3) Remove rear wheel and tire assembly.
(4) Remove caliper and anchor as an assembly.
(5) Remove rubber access plug from back of rear
disc brake splash shield.
(6) If necessary retract parking brake shoes with
brake adjuster tool (Fig. 82). Position tool at top of
star wheel and rotate wheel.
(7) Remove rotor from axle hub flange.
(8) Remove the lower shoe to shoe spring/adjuster
spring with needle nose pliers (Fig. 83).
(9) Remove the upper shoe to shoe spring/return
spring with brake pliers (Fig. 84).(10) Remove shoe hold-down clips and pins (Fig.
85). Clip is held in place by pin which fits in clip
notch. To remove clip, first push clip ends together
and slide clip until head of pin clears narrow part of
notch. Then remove clip and pin.
(11) Remove shoes and adjuster.
INSTALLATION
(1) Install shoes on splash shield with hold down
clips and pins. Be sure shoes are properly engaged in
the park brake actuator.
(2) Lubricate and install adjuster screw assembly.
Be sure notched ends of screw assembly are properly
seated on shoes and that star wheel is aligned with
access hole in shield.
Fig. 80 Parking Brake Lever Mounting
1 - MOUNTING NUT
2 - PARK BRAKE LEVER
Fig. 81 Lock Out Spring
1 - LOCK OUT SPRING
Fig. 82 Retracting Parking Brake Shoes
1 - ACCESS HOLE
2 - BRAKE ADJUSTING TOOL
3 - SPLASH SHIELD
WJBRAKES - BASE 5 - 39
LEVER (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

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)

DESCRIPTION N´m Ft. In.
Lbs. Lbs.
4.0L 4 Ð 32
4.7L 2 Ð 17
Fan Blade Assy. to Viscous
DriveÐ
Bolts 4.0L 23 Ð 200
Generator MountingÐBolts
4.0L57 42 Ð
Radiator Upper Isolator to
CrossmemberÐNuts 3 Ð 20
Radiator Upper Isolator to
RadiatorÐ
Nuts 4 Ð 36
Radiator BraceÐBolts 10 Ð 90
Thermostat HousingÐBolts
4.0L 22 16 Ð
4.7L 13 Ð 115
Upper Radiator Crossmember
to
BodyÐBolts 10 Ð 90
Water PumpÐBolts
4.0L 23 17 Ð
4.7L 54 40 Ð
Water Pump Pulley to Water
PumpÐ
Bolts 4.0L 28 Ð 250
High Pressure Inlet Hose to
Hydraulic Fan DriveÐ1/2 inch
Fitting49 36 Ð
High Pressure Outlet Hose to
Steering GearÐ3/8 inch
Fitting29 21.5 Ð
Fan Shroud to Radiator
Mounting Bolts6Ð50SPECIAL TOOLS
COOLING
Pliers 6094
Pressure Tester 7700±A
WJCOOLING 7 - 15
COOLING (Continued)

SERPENTINE DRIVE BELT DIAGNOSIS CHART
CONDITION POSSIBLE CAUSES CORRECTION
RIB CHUNKING (ONE OR MORE
RIBS HAS SEPARATED FROM
BELT BODY)1. Foreign objects imbedded in pulley
grooves.1. Remove foreign objects from
pulley grooves. Replace belt.
2. Installation damage. 2. Replace belt.
RIB OR BELT WEAR 1. Pulley(s) misaligned. 1. Align pulley(s).
2. Abrasive environment. 2. Clean pulley(s). Replace belt if
necessary.
3. Rusted pulley(s). 3. Clean rust from pulley(s).
4. Sharp or jagged pulley groove tips. 4. Replace pulley.
5. Rubber deteriorated. 5. Replace belt.
LONGITUDINAL BELT
CRACKING (CRACKS BETWEEN
TWO RIBS)1. Belt has mistracked from pulley
groove.1. Replace belt.
2. Pulley groove tip has worn away
rubber to tensile member.2. Replace belt.
BELT SLIPS 1. Belt slipping because of insufficient
tension.1. Replace automatic belt tensioner.
2. Belt routed 2. Verify belt routing.
incorrectly
3. Incorrect belt. 3. Replace belt.
4. Belt or pulley subjected to
substance (belt dressing, oil ethylene
glycol) that has reduced friction.4. Replace belt and clean pulleys.
5. Driven component bearing failure. 5. Replace faulty component
bearing.
6. Belt glazed and hardened from
heat and excessive slippage.6. Replace belt.
ªGROOVE JUMPING9(BELT
DOES NOT MAINTAIN CORRECT
POSITION ON PULLEY)1. Belt tension either too high or too
low.1. Replace automatic belt tensioner.
2. Belt routed 2. Verify belt routing.
incorrectly.
3. Incorrect belt. 3. Replace belt.
4. Pulley(s) not within design
tolerance.4. Replace pulley(s).
5. Foreign object(s) in grooves. 5. Remove foreign objects from
grooves.
6. Pulley misalignment. 6. Check and replace.
7. Belt cord line is broken. 7. Replace belt.
7 - 18 ACCESSORY DRIVEWJ
DRIVE BELTS - 4.0L (Continued)

SERPENTINE DRIVE BELT DIAGNOSIS CHART
CONDITION POSSIBLE CAUSES CORRECTION
RIB CHUNKING (ONE OR MORE
RIBS HAS SEPARATED FROM
BELT BODY)1. Foreign objects imbedded in pulley
grooves.1. Remove foreign objects from
pulley grooves. Replace belt.
2. Installation damage. 2. Replace belt.
RIB OR BELT WEAR 1. Pulley(s) misaligned. 1. Align pulley(s).
2. Abrasive environment. 2. Clean pulley(s). Replace belt if
necessary.
3. Rusted pulley(s). 3. Clean rust from pulley(s).
4. Sharp or jagged pulley groove tips. 4. Replace pulley.
5. Rubber deteriorated. 5. Replace belt.
LONGITUDINAL BELT
CRACKING (CRACKS BETWEEN
TWO RIBS)1. Belt has mistracked from pulley
groove.1. Replace belt.
2. Pulley groove tip has worn away
rubber to tensile member.2. Replace belt.
BELT SLIPS 1. Belt slipping because of insufficient
tension.1. Replace automatic belt tensioner.
2. Belt routed 2. Verify belt routing.
incorrectly
3. Incorrect belt. 3. Replace belt.
4. Belt or pulley subjected to
substance (belt dressing, oil ethylene
glycol) that has reduced friction.4. Replace belt and clean pulleys.
5. Driven component bearing failure. 5. Replace faulty component
bearing.
6. Belt glazed and hardened from
heat and excessive slippage.6. Replace belt.
ªGROOVE JUMPING9(BELT
DOES NOT MAINTAIN CORRECT
POSITION ON PULLEY)1. Belt tension either too high or too
low.1. Replace automatic belt tensioner.
2. Belt routed 2. Verify belt routing.
incorrectly.
3. Incorrect belt. 3. Replace belt.
4. Pulley(s) not within design
tolerance.4. Replace pulley(s).
5. Foreign object(s) in grooves. 5. Remove foreign objects from
grooves.
6. Pulley misalignment. 6. Check and replace.
7. Belt cord line is broken. 7. Replace belt.
WJACCESSORY DRIVE 7 - 21
DRIVE BELTS - 4.7L (Continued)

(6) Start the engine and operate at 2400 rpm.
Within ten minutes the air temperature (indicated on
the dial thermometer) should be up to 93É C (200É F).
Fan driveengagementshould have started to occur
at between 91É to 96É C (195É to 205É F). Engage-
ment is distinguishable by a definiteincreasein fan
flow noise (roaring). The timing light also will indi-
cate an increase in the speed of the fan.
(7) When the air temperature reaches 93É C (200É
F), remove the plastic sheet. Fan drivedisengage-
mentshould have started to occur at between 62É to
85É C (145É to 185É F). A definitedecreaseof fan
flow noise (roaring) should be noticed. If not, replace
the defective viscous fan drive unit.
PWM FAN CONTROL MODULE -
4.0L
DESCRIPTION
The pulse width modulated (PWM) radiator cooling
fan relay is located behind the front bumper fascia
below the right headlamp.
OPERATION
The PWM relay is used to control the speed of the
electric radiator cooling fan. It allows for multiple fan
speeds. This allows for improved fan noise and A/C
performance, better engine cooling, and additional
vehicle power.
PWM relay operation is controlled by the Power-
train Control Module (PCM). To operate the PWM
relay, the PCM looks at inputs from:
²Engine coolant temperature
²Ambient temperature from the body controller
²Vehicle speed
²Transmission oil temperature
²A/C switch position (A/C request)
REMOVAL
The Pulse Width Modulated (PWM) cooling fan
relay is located below the right headlamp behind the
bumper fascia (Fig. 28).
(1) Remove front bumper and grill assembly.
(2) Remove 1 support bolt near front of reservoir
(Fig. 28).
(3) Remove 2 reservoir mounting bolts.
(4) Remove reservoir from vehicle to gain access to
vacuum hose (Fig. 29). Disconnect vacuum hose from
reservoir fitting at rear of reservoir.
(5) Disconnect electrical connector at relay (Fig.
30).
(6) Remove 2 relay mounting bolts (Fig. 30) and
remove relay.
Fig. 28 Radiator Cooling Fan Relay Location
1 - RADIATOR FAN RELAY
2 - VACUUM RESERVOIR
3 - BOLT
4 - RIGHT FRONT FENDER
Fig. 29 Vacuum Reservoir Removal/Installation
1 - VACUUM HOSE
2 - RADIATOR
3 - VACUUM RESERVOIR
WJENGINE 7 - 41
FAN DRIVE VISCOUS CLUTCH - 4.0L (Continued)