2003 JEEP GRAND CHEROKEE Engine systems

GROUP TAB LOCATOR
Introduction
0Lubrication & Maintenance
2Suspension
3Driveline
5Brakes
7Cooling
8AAudio
8BChime/Buzzer
8EElectronic Control Modules
8FEngine Systems
8GHeated Systems
8HHorn
8IIgnition Control
8JInstrument Cluster
8LLamps
8MMessage Systems
8NPower Systems
8ORestraints
8PSpeed Control
8QVehicle Theft Security
8RWipers/Washers
8WWiring
9Engine
11Exhaust System
13Frame & Bumpers
14Fuel System
19Steering
21Transaxle
22Tires/Wheels
23Body
24Heating & Air Conditioning
25Emissions Control
Service Manual Comment Forms (Rear of Manual)

JUMP STARTING
STANDARD PROCEDURE - JUMP STARTING
WARNING: REVIEW ALL SAFETY PRECAUTIONS
AND WARNINGS IN GROUP 8A, BATTERY/START-
ING/CHARGING SYSTEMS DIAGNOSTICS. DO NOT
JUMP START A FROZEN BATTERY, PERSONAL
INJURY CAN RESULT. DO NOT JUMP START WHEN
MAINTENANCE FREE BATTERY INDICATOR DOT IS
YELLOW OR BRIGHT COLOR. DO NOT JUMP
START A VEHICLE WHEN THE BATTERY FLUID IS
BELOW THE TOP OF LEAD PLATES. DO NOT
ALLOW JUMPER CABLE CLAMPS TO TOUCH
EACH OTHER WHEN CONNECTED TO A BOOSTER
SOURCE. DO NOT USE OPEN FLAME NEAR BAT-
TERY. REMOVE METALLIC JEWELRY WORN ON
HANDS OR WRISTS TO AVOID INJURY BY ACCI-
DENTAL ARCING OF BATTERY CURRENT. WHEN
USING A HIGH OUTPUT BOOSTING DEVICE, DO
NOT ALLOW BATTERY VOLTAGE TO EXCEED 16
VOLTS. REFER TO INSTRUCTIONS PROVIDED
WITH DEVICE BEING USED.
CAUTION: When using another vehicle as a
booster, do not allow vehicles to touch. Electrical
systems can be damaged on either vehicle.
TO JUMP START A DISABLED VEHICLE:
(1) Raise hood on disabled vehicle and visually
inspect engine compartment for:
²Battery cable clamp condition, clean if necessary.
²Frozen battery.
²Yellow or bright color test indicator, if equipped.
²Low battery fluid level.
²Generator drive belt condition and tension.
²Fuel fumes or leakage, correct if necessary.
CAUTION: If the cause of starting problem on dis-
abled vehicle is severe, damage to booster vehicle
charging system can result.
(2) When using another vehicle as a booster
source, park the booster vehicle within cable reach.
Turn off all accessories, set the parking brake, place
the automatic transmission in PARK or the manual
transmission in NEUTRAL and turn the ignition
OFF.
(3) On disabled vehicle, place gear selector in park
or neutral and set park brake. Turn off all accesso-
ries.
(4) Connect jumper cables to booster battery. RED
clamp to positive terminal (+). BLACK clamp to neg-
ative terminal (-). DO NOT allow clamps at opposite
end of cables to touch, electrical arc will result.
Review all warnings in this procedure.
(5) On disabled vehicle, connect RED jumper cable
clamp to positive (+) terminal. Connect BLACK
jumper cable clamp to engine ground as close to the
ground cable attaching point as possible (Fig. 8).
(6) Start the engine in the vehicle which has the
booster battery, let the engine idle a few minutes,
then start the engine in the vehicle with the dis-
charged battery.
CAUTION: Do not crank starter motor on disabled
vehicle for more than 15 seconds, starter will over-
heat and could fail.
(7) Allow battery in disabled vehicle to charge to
at least 12.4 volts (75% charge) before attempting to
start engine. If engine does not start within 15 sec-
onds, stop cranking engine and allow starter to cool
(15 min.), before cranking again.
Fig. 7 Correct Vehicle Lifting Locations
WJLUBRICATION & MAINTENANCE 0 - 7
LIFT POINTS (Continued)

and therefore creates pressure in the pump. The tun-
ing of the front and rear axle orifices and valves
inside the gerotor pump is unique and each system
includes a torque-limiting pressure relief valve to
protect the clutch pack, which also facilitates vehicle
control under extreme side-to-side traction varia-
tions. The resulting pressure is applied to the clutch
pack and the transfer of torque is completed.
Under conditions in which opposite wheels are on
surfaces with widely different friction characteristics,
Vari-loktdelivers far more torque to the wheel on
the higher traction surface than do conventional
Trac-loktsystems. Because conventional Trac-lokt
differentials are initially pre-loaded to assure torque
transfer, normal driving (where inner and outer
wheel speeds differ during cornering, etc.) produces
torque transfer during even slight side-to-side speed
variations. Since these devices rely on friction from
this preload to transfer torque, normal use tends to
cause wear that reduces the ability of the differential
to transfer torque over time. By design, the Vari-lokt
system is less subject to wear, remaining more con-
sistent over time in its ability to transfer torque. The
coupling assembly is serviced as a unit. From a ser-
vice standpoint the coupling also benefits from using
the same lubricant supply as the ring and pinion
gears.
DIAGNOSIS AND TESTING
GEAR NOISE
Axle gear noise can be caused by insufficient lubri-
cant, incorrect backlash, tooth contact, worn/damaged
gears, or the carrier housing not having the proper
offset and squareness.
Gear noise usually happens at a specific speed
range. The noise can also occur during a specific type
of driving condition. These conditions are accelera-
tion, deceleration, coast, or constant load.
When road testing, first warm-up the axle fluid by
driving the vehicle at least 5 miles and then acceler-
ate the vehicle to the speed range where the noise is
the greatest. Shift out-of-gear and coast through the
peak-noise range. If the noise stops or changes
greatly:
²Check for insufficient lubricant.
²Incorrect ring gear backlash.
²Gear damage.
Differential side gears and pinions can be checked
by turning the vehicle. They usually do not cause
noise during straight-ahead driving when the gears
are unloaded. The side gears are loaded during vehi-
cle turns. A worn pinion mate shaft can also cause a
snapping or a knocking noise.
BEARING NOISE
The axle shaft, differential and pinion bearings can
all produce noise when worn or damaged. Bearing
noise can be either a whining, or a growling sound.
Pinion bearings have a constant-pitch noise. This
noise changes only with vehicle speed. Pinion bearing
noise will be higher pitched because it rotates at a
faster rate. Drive the vehicle and load the differen-
tial. If bearing noise occurs, the rear pinion bearing
is the source of the noise. If the bearing noise is
heard during a coast, the front pinion bearing is the
source.
Worn or damaged differential bearings usually pro-
duce a low pitch noise. Differential bearing noise is
similar to pinion bearing noise. The pitch of differen-
tial bearing noise is also constant and varies only
with vehicle speed.
Axle shaft bearings produce noise and vibration
when worn or damaged. The noise generally changes
when the bearings are loaded. Road test the vehicle.
Turn the vehicle sharply to the left and to the right.
This will load the bearings and change the noise
level. Where axle bearing damage is slight, the noise
is usually not noticeable at speeds above 30 mph.
LOW SPEED KNOCK
Low speed knock is generally caused by a worn
U-joint or by worn side±gear thrust washers. A worn
pinion shaft bore will also cause low speed knock.
VIBRATION
Vibration at the rear of the vehicle is usually
caused by a:
²Damaged drive shaft.
²Missing drive shaft balance weight(s).
²Worn or out-of-balance wheels.
²Loose wheel lug nuts.
²Worn U-joint(s).
²Loose/broken springs.
²Damaged axle shaft bearing(s).
²Loose pinion gear nut.
²Excessive pinion yoke run out.
²Bent axle shaft(s).
Check for loose or damaged front-end components
or engine/transmission mounts. These components
can contribute to what appears to be a rearend vibra-
tion. Do not overlook engine accessories, brackets
and drive belts.
All driveline components should be examined
before starting any repair.
(Refer to 22 - TIRES/WHEELS - DIAGNOSIS AND
TESTING)
3 - 92 REAR AXLE - 226RBAWJ
REAR AXLE - 226RBA (Continued)

PRESSURE HOLD
Both solenoid valves are closed in the pressure
hold cycle. Fluid apply pressure in the control chan-
nel is maintained at a constant rate. The CAB main-
tains the hold cycle until sensor inputs indicate a
pressure change is necessary.
PRESSURE INCREASE
The inlet valve is open and the outlet valve is
closed during the pressure increase cycle. The pres-
sure increase cycle is used to counteract unequal
wheel speeds. This cycle controls re-application of
fluid apply pressure due to changing road surfaces or
wheel speed.
REMOVAL
(1) Remove the negative battery cable from the
battery.
(2) Remove the air cleaner housing,(Refer to 9 -
ENGINE/AIR INTAKE SYSTEM/AIR CLEANER
HOUSING - REMOVAL).
(3) Pull the CAB harness connector release up and
remove connector (Fig. 10).(4) Remove the brake lines from the HCU.
(5) Remove the HCU/CAB side mounting bolt and
the two rear mounting bolts. (Fig. 11).
(6) Remove the HCU/CAB assembly from the vehi-
cle.
INSTALLATION
(1) Install HCU/CAB assembly into the mounting
bracket and tighten mounting bolts to 12 N´m (9 ft.
lbs.).
(2) Install the brake lines to the HCU and tighten
to 16 N´m (12 ft. lbs.).
(3) Install CAB harness connector and push down
connector release.
(4) Install air cleaner housing,(Refer to 9 -
ENGINE/AIR INTAKE SYSTEM/AIR CLEANER
HOUSING - INSTALLATION).
(5) Install negative battery cable to the battery.
(6) Bleed base and ABS brake systems,(Refer to 5 -
BRAKES - STANDARD PROCEDURE) OR (Refer to
5 - BRAKES - STANDARD PROCEDURE).
Fig. 10 CAB Connector Release
1 - CONNECTOR RELEASE
2 - CAB
Fig. 11 HCU/CAB Assembly
1 - SIDE MOUNTING BOLT
2 - REAR MOUNTING BOLTS
WJBRAKES - ABS 5 - 47
HCU (HYDRAULIC CONTROL UNIT) (Continued)

corrosion inhibitors called HOAT, for Hybrid Organic
Additive Technology) is recommended. This coolant
offers the best engine cooling without corrosion when
mixed with 50% distilled water to obtain to obtain a
freeze point of -37ÉC (-35ÉF). If it loses color or
becomes contaminated, drain, flush, and replace with
fresh properly mixed coolant solution.
CAUTION: Do not use coolant additives that are
claimed to improve engine cooling.
STANDARD PROCEDURE - COOLING SYSTEM -
REVERSE FLUSHING
CAUTION: The cooling system normally operates at
97-to-124 kPa (14-to -18 psi) pressure. Exceeding
this pressure may damage the radiator or hoses.
Reverse flushing of the cooling system is the forc-
ing of water through the cooling system. This is done
using air pressure in the opposite direction of normal
coolant flow. It is usually only necessary with very
dirty systems with evidence of partial plugging.
CHEMICAL CLEANING
If visual inspection indicates the formation of
sludge or scaly deposits, use a radiator cleaner
(Mopar Radiator Kleen or equivalent) before flushing.
This will soften scale and other deposits and aid the
flushing operation.
CAUTION: Be sure instructions on the container are
followed.
REVERSE FLUSHING RADIATOR
Disconnect the radiator hoses from the radiator fit-
tings. Attach a section of radiator hose to the radia-
tor bottom outlet fitting and insert the flushing gun.
Connect a water supply hose and air supply hose to
the flushing gun.
CAUTION: The cooling system normally operates at
97-to-124 kPa (14- to-18 psi) pressure. Exceeding
this pressure may damage the radiator or hoses.
Allow the radiator to fill with water. When radiator
is filled, apply air in short blasts allowing radiator to
refill between blasts. Continue this reverse flushing
until clean water flows out through rear of radiator
cooling tube passages. For more information, refer to
operating instructions supplied with flushing equip-
ment. Have radiator cleaned more extensively by a
radiator repair shop.
REVERSE FLUSHING ENGINE
Drain the cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE). Remove the thermostat
housing and thermostat. Install the thermostat hous-
ing. Disconnect the radiator upper hose from the
radiator and attach the flushing gun to the hose. Dis-
connect the radiator lower hose from the water
pump. Attach a lead away hose to the water pump
inlet fitting.
CAUTION: Be sure that the heater control valve is
closed (heat off). This is done to prevent coolant
flow with scale and other deposits from entering
the heater core.
Connect the water supply hose and air supply hose
to the flushing gun. Allow the engine to fill with
water. When the engine is filled, apply air in short
blasts, allowing the system to fill between air blasts.
Continue until clean water flows through the lead
away hose. For more information, refer to operating
instructions supplied with flushing equipment.
Remove the lead away hose, flushing gun, water
supply hose and air supply hose. Remove the thermo-
stat housing (Refer to 7 - COOLING/ENGINE/EN-
GINE COOLANT THERMOSTAT - REMOVAL).
Install the thermostat and housing with a replace-
ment gasket (Refer to 7 - COOLING/ENGINE/EN-
GINE COOLANT THERMOSTAT -
INSTALLATION). Connect the radiator hoses. Refill
the cooling system with the correct antifreeze/water
mixture (Refer to 7 - COOLING - STANDARD PRO-
CEDURE).
SPECIFICATIONS
TORQUE
DESCRIPTION N´m Ft. In.
Lbs. Lbs.
Automatic Belt Tensioner to
Mounting
BracketÐBolt
4.0L 28 Ð 250
4.7L 41 30 Ð
Automatic Belt Tensioner
PulleyÐ
Bolt
(4.7L) 61 45 Ð
Block HeaterÐBolt
7 - 14 COOLINGWJ
COOLING (Continued)

²Fan control valve
²Two stage G-rotor hydraulic drive
The hydraulic fan and drive is not serviceable.
Therefore any failure of the fan blade, hydraulic fan
drive or fan shroud requires replacement of the fan
module because the fan blade and hydraulic fan drive
are matched and balanced as a system and servicing
either separately would disrupt this balance.
For hydraulic fluid routing information refer to
(Fig. 5).
CAUTION: Do not attempt to service the hydraulic
cooling fan or fan drive separately replace the cooling
module as an assembly. Failure to do so may cause
severe damage to the hydraulic cooling fan assembly.
OPERATION
The hydraulic radiator cooling fan used on the
Grand Cherokee with the 4.7L engine replaces both
the electric fan and the engine driven mechanical
fan. The use of this hydraulic fan provides the 4.7L
equipped Grand Cherokee with heavy trailer tow
capability while at the same time reducing unneces-
sary power drain on both the engine and the vehicles
electrical system.
HYDRAULIC FAN STRATEGY
The hydraulic radiator cooling fan is controlled by
the JTEC. A PWM (Pulse With Modulated) signal
from the JTEC controls the fan from 0 to 100% of the
available fan speed. There are four inputs to the
JTEC that determine what speed percentage of fan is
required by the vehicle. These inputs are:
²Engine Coolant Temperature
²Transmission Oil Temperature
²Battery Temperature
²A/C System Pressure
By monitoring these four parameters, the JTEC
can determine if cooling airflow is required. If airflow
is required, the JTEC will slowly ramp up (speed up)
the fan speed until the parameter(s) are under con-
trol. Once the temperature or pressure is reduced to
within operating parameters the fan will ramp up,
ramp down, or hold its speed to maintain the temper-
ature / pressure requirements.
NOTE: Even if the JTEC is not requesting fan on
operation the fan blade will usually spin between
100 and 500 RPM when the vehicle is at idle. This is
due to a controlled minimum oil flow requirement
through the fan drive motor.
ACTIVATING THE HYDRAULIC FAN WITH THE DRB
Under the Engine Systems test heading, there is a
subheading. ªHydraulic fan solenoid testº, that has
the selections, on /off. Activating the fan with the
DRB will run the fan at 100% duty cycle, which will
help troubleshoot any system problems, and also help
with the deaeration procedure.
NOTE: Engine must be running to activate the fan
with the DRB.
RADIATOR COOLING FAN HYDRAULIC FLUID PATH
Hydraulic fluid is pumped through the power
steering pump, from the pump the fluid travels
though a high pressure delivery line to the fan drive
motor. As fluid is diverted through the G-rotors, rota-
tional motion is created as fluid moves from the high-
pressure (inlet) side of the motor to the low-pressure
(outlet) side. Fluid exiting the drive motor is divided
into two paths. Path one continues through a high
pressure delivery line to the vehicles steering gear to
provide steering assist. and path two sends fluid
back to the power steering pump through a low pres-
sure line. Fluid exits the steering gear under low
pressure and travels through a low pressure line to
the power steering fluid cooler to be cooled before
being returned back the the power steering fluid res-
ervoir (Fig. 5).
Fig. 4 HYDRAULIC RADIATOR COOLING FAN AND
FAN DRIVE
1 - POWER STEERING FLUID COOLER
2 - RADIATOR
3 - HIGH PRESSURE LINE FROM STEERING GEAR PUMP TO
HYDRAULIC FAN MOTOR
4 - HYDRAULIC FAN MOTOR
5 - HIGH PRESSURE LINE FROM HYDRAULIC FAN MOTOR TO
STEERING GEAR
6 - FAN SHROUD
7 - 28 ENGINEWJ
RADIATOR FAN - 4.7L (Continued)

AUDIO
TABLE OF CONTENTS
page page
AUDIO
DESCRIPTION..........................2
OPERATION............................3
DIAGNOSIS AND TESTING - AUDIO..........3
SPECIAL TOOLS
AUDIO SYSTEMS......................6
AMPLIFIER
DESCRIPTION..........................6
OPERATION............................6
DIAGNOSIS AND TESTING - AMPLIFIER......6
REMOVAL.............................6
INSTALLATION..........................6
ANTENNA BODY & CABLE
DESCRIPTION..........................7
OPERATION............................7
DIAGNOSIS AND TESTING - ANTENNA BODY
AND CABLE..........................7
REMOVAL.............................9
INSTALLATION.........................10
ANTENNA MODULE - EXPORT
DESCRIPTION.........................10
OPERATION...........................11
DIAGNOSIS AND TESTING - ANTENNA
MODULE - EXPORT....................11
REMOVAL.............................12
INSTALLATION.........................12
CD CHANGER
DESCRIPTION.........................12
OPERATION...........................13
DIAGNOSIS AND TESTING - CD CHANGER . . . 13
REMOVAL.............................14
INSTALLATION.........................14
INSTRUMENT PANEL ANTENNA CABLE
REMOVAL.............................15
INSTALLATION.........................15
QUARTER GLASS INTEGRAL ANTENNA -
EXPORT
DESCRIPTION.........................16
OPERATION...........................16
DIAGNOSIS AND TESTING - QUARTER
GLASS INTEGRAL ANTENNA - EXPORT....16RADIO
DESCRIPTION.........................16
OPERATION...........................16
DIAGNOSIS AND TESTING - RADIO.........16
REMOVAL.............................17
INSTALLATION.........................18
RADIO NOISE SUPPRESSION GROUND STRAP
DESCRIPTION.........................18
REMOVAL
REMOVAL - ENGINE-TO-BODY GROUND
STRAP.............................18
REMOVAL - EXHAUST-TO-BODY GROUND
STRAP.............................19
INSTALLATION
INSTALLATION - ENGINE TO BODY
GROUND STRAP......................19
INSTALLATION - EXHAUST-TO-BODY
GROUND STRAP......................19
REMOTE SWITCHES
DESCRIPTION.........................19
OPERATION...........................20
DIAGNOSIS AND TESTING - REMOTE
SWITCHES..........................20
REMOVAL.............................21
INSTALLATION.........................21
SPEAKER
DESCRIPTION.........................22
OPERATION...........................22
DIAGNOSIS AND TESTING - SPEAKER......23
REMOVAL
REAR DOOR SPEAKER................24
INSTRUMENT PANEL SPEAKER..........24
FRONT DOOR SPEAKER...............24
INSTALLATION
INSTALLATION - REAR DOOR SPEAKER . . . 25
INSTALLATION - INSTRUMENT PANEL
SPEAKER...........................25
INSTALLATION - FRONT DOOR SPEAKER . . 25
WJAUDIO 8A - 1

AUDIO
DESCRIPTION
An audio system is standard factory-installed
equipment on this model. The standard equipment
audio system includes an AM/FM/cassette (RBB sales
code) radio receiver, and speakers in six locations.
Several combinations of radio receivers and speaker
systems are offered as optional equipment on this
model. The audio system uses an ignition switched
control of battery current so that the system will only
operate when the ignition switch is in the On or
Accessory positions.
A Compact Disc (CD) changer with a ten disc mag-
azine, remote radio switches with six functions
mounted to the backs of the steering wheel spokes,
and a memory system that automatically stores and
recalls up to twenty radio station presets (ten AM
and ten FM) and the last station listened to for two
drivers are optional factory-installed equipment on
this model. Refer to Electrical, Power Seats for more
information on the memory system.
The audio system includes the following compo-
nents:
²Antenna
²Compact disc changer (available with RBP sales
code radio receivers only)
²Power amplifier (with premium speaker system
only)
²Radio noise suppression components
²Radio receiver
²Remote radio switches
²Speakers
Certain functions and features of the audio system
rely upon resources shared with other electronic
modules in the vehicle over the Programmable Com-
munications Interface (PCI) data bus network. The
PCI data bus network allows the sharing of sensor
information. This helps to reduce wire harness com-
plexity, internal controller hardware, and component
sensor current loads. At the same time, this system
provides increased reliability, enhanced diagnostics,
and allows the addition of many new feature capabil-
ities. For diagnosis of these electronic modules or of
the PCI data bus network, the use of a DRB scan
tool and the proper Diagnostic Procedures manual
are recommended.
The other electronic modules that may affect audio
system operation are as follows:
²Body Control Module (BCM)- (Refer to 8 -
ELECTRICAL/ELECTRONIC CONTROL MOD-
ULES/BODY CONTROL/CENTRAL TIMER MODUL
- DESCRIPTION) for more information.
²Driver Door Module (DDM)(Refer to 8 -
ELECTRICAL/ELECTRONIC CONTROL MOD-ULES/DRIVER DOOR MODULE - DESCRIPTION)
for more information.
²Passenger Door Module (PDM)(Refer to 8 -
ELECTRICAL/ELECTRONIC CONTROL MOD-
ULES/DRIVER DOOR MODULE - DESCRIPTION)
for more information.
The audio system includes the following major
components, which are described in further detail
elsewhere in this service information:
²Amplifier- On models equipped with the
optional premium speaker system, an audio power
amplifier is located on the rear floor panel under-
neath the right end of the rear seat cushion in the
passenger compartment.
²Antenna Body and Cable- The most visible
component of the antenna body and cable are the
antenna adapter and the antenna cap nut, which are
located on the top of the right front fender panel of
the vehicle, near the right end of the cowl plenum.
²Antenna Mast- The antenna mast is a metal
rod that extends upward from the antenna body and
cable on the top of the right front fender panel of the
vehicle, near the right end of the cowl plenum.
²Radio- The radio for this model is located in
the instrument panel center stack area, inboard of
the instrument cluster and above the heater and air
conditioner controls.
²Radio Noise Suppression Ground Strap-A
radio noise suppression ground strap is installed
between the rear of the engine cylinder head(s) and
the dash panel sheet metal in the engine compart-
ment.
²Speaker- The standard speaker system
includes six speakers in six locations, while the pre-
mium speaker system includes an amplifier for the
six speakers in six locations.
Hard wired circuitry connects the audio system
components to each other through the electrical sys-
tem of the vehicle. These hard wired circuits are
integral to several wire harnesses, which are routed
throughout the vehicle and retained by many differ-
ent methods. These circuits may be connected to each
other, to the vehicle electrical system and to the
audio system components through the use of a com-
bination of soldered splices, splice block connectors
and many different types of wire harness terminal
connectors and insulators. Refer to the appropriate
wiring information in this service manual for com-
plete standard and premium audio system circuit
diagrams. The wiring information includes proper
wire and connector repair procedures, further details
on wire harness routing and retention, as well as
pin-out and location views for the various wire har-
ness connectors, splices, and grounds.
8A - 2 AUDIOWJ