2003 JEEP GRAND CHEROKEE Power System

(3) Raise vehicle.
(4) Remove engine cylinder block drain plug(s)
located on the sides of cylinder block above the oil
pan rail (Fig. 16).
(5) Remove power cord from block heater.(6) Loosen screw at center of block heater. Remove
heater assembly (Fig. 17).
REMOVALÐ4.0L ENGINE
(1) Disconnect negative battery cable from battery.
(2) Drain coolant from radiator (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(3) Raise vehicle.
(4) Remove engine cylinder block drain plug(s)
located on the sides of cylinder block above the oil
pan rail (Fig. 18).
(5) Remove power cord from block heater.
(6) Loosen screw at center of block heater. Remove
heater assembly (Fig. 19).
INSTALLATION
INSTALLATIONÐ4.7L ENGINE
(1) Thoroughly clean cylinder block core hole and
block heater seat.
(2) Insert block heater assembly with element loop
pointing at twelve o'clock (Fig. 17).
(3) With block heater fully seated, tighten center
screw to 2 N´m (17 in. lbs.) torque.
(4) Refill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(5) Start and warm the engine. Check for leaks.
INSTALLATIONÐ4.0L ENGINE
(1) Thoroughly clean cylinder block core hole and
block heater seat.
Fig. 15 Engine Block Heater 4.7L Engine
1 - ENGINE BLOCK HEATER
Fig. 16 Drain Plug - 4.7L Engine
1 - CYLINDER BLOCK DRAIN PLUG
2 - EXHAUST MANIFOLD AND HEAT SHIELD
Fig. 17 Engine Block Heater - 4.7L
1 - ENGINE BLOCK HEATER
7 - 34 ENGINEWJ
ENGINE BLOCK HEATER (Continued)

(2) Insert block heater assembly with element loop
pointing at twelve o'clock (Fig. 19).
(3) With block heater fully seated, tighten center
screw to 2 N´m (17 in. lbs.) torque.
(4) Refill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(5) Start and warm the engine. Check for leaks.
ENGINE COOLANT TEMP
SENSOR
DESCRIPTION
The Engine Coolant Temperature (ECT) sensor is
used to sense engine coolant temperature. The sensor
protrudes into an engine water jacket.
The ECT sensor is a two-wire Negative Thermal
Coefficient (NTC) sensor. Meaning, as engine coolant
temperature increases, resistance (voltage) in the
sensor decreases. As temperature decreases, resis-
tance (voltage) in the sensor increases.
OPERATION
At key-on, the Powertrain Control Module (PCM)
sends out a regulated 5 volt signal to the ECT sensor.
The PCM then monitors the signal as it passes
through the ECT sensor to the sensor ground (sensor
return).
When the engine is cold, the PCM will operate in
Open Loop cycle. It will demand slightly richer air-
fuel mixtures and higher idle speeds. This is done
until normal operating temperatures are reached.
The PCM uses inputs from the ECT sensor for the
following calculations:
²for engine coolant temperature gauge operation
through CCD or PCI (J1850) communications
²Injector pulse-width
²Spark-advance curves
²ASD relay shut-down times
²Idle Air Control (IAC) motor key-on steps
²Pulse-width prime-shot during cranking
²O2 sensor closed loop times
²Purge solenoid on/off times
²EGR solenoid on/off times (if equipped)
²Leak Detection Pump operation (if equipped)
²Radiator fan relay on/off times (if equipped)
²Target idle speed
REMOVAL
REMOVALÐ4.0L ENGINE
WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING. COOLING SYSTEM
MUST BE PARTIALLY DRAINED BEFORE REMOV-
ING THE ENGINE COOLANT TEMPERATURE (ECT)
SENSOR. REFER TO GROUP 7, COOLING.
(1) Partially drain cooling system. (Refer to 7 -
COOLING - STANDARD PROCEDURE).
Fig. 18 Drain Plug
1 - COOLANT TEMPERATURE SENSOR
2 - BLOCK DRAIN PLUG
Fig. 19 Engine Block Heater
1 - ENGINE BLOCK HEATER
WJENGINE 7 - 35
ENGINE BLOCK HEATER (Continued)

(4) Remove two radiator mounting bolts.
(5) Disconnect both transmission cooler lines from
radiator.
(6) Disconnect electrical connector for the fan con-
trol solenoid.
(7) Disconnect the power steering cooler line from
cooler and filter.
(8) Disconnect the radiator upper and lower hoses.
(9) Disconnect the overflow hose from radiator.
(10) Remove the air inlet duct at the grill.(11) The lower part of radiator is equipped with
two alignment dowel pins (Fig. 35). They are located
on the bottom of radiator tank and fit into rubber
grommets. These rubber grommets are pressed into
the radiator lower crossmember.
WARNING: THE AIR CONDITIONING SYSTEM (IF
EQUIPPED) IS UNDER A CONSTANT PRESSURE
EVEN WITH THE ENGINE OFF. REFER TO REFRIG-
ERANT WARNINGS IN, HEATING AND AIR CONDI-
TIONING BEFORE HANDLING ANY AIR
CONDITIONING COMPONENT.
NOTE: The radiator and radiator cooling fan can be
removed as an assembly. It is not necessary to
remove the cooling fan before removing or install-
ing the radiator.
(12) Disconnect the two high pressure fluid lines
at the hydraulic fan drive.
(13) Disconnect the low pressure return hose at
the hydraulic fan drive.
(14) Gently lift up and remove radiator from vehi-
cle. Be careful not to scrape the radiator fins against
any other component. Also be careful not to disturb
the air conditioning condenser (if equipped).
CLEANING
Clean radiator fins With the engine cold, apply cold
water and compressed air to the back (engine side) of
Fig. 32 Hose Clamp Tool - Typical
1 - HOSE CLAMP TOOL 6094
2 - HOSE CLAMP
Fig. 33 Clamp Number/Letter Location - Typical
1 - TYPICAL CONSTANT TENSION HOSE CLAMP
2 - CLAMP NUMBER/LETTER LOCATION
3 - TYPICAL HOSE
Fig. 34 Air Seals - Typical
1 - AIR DAM
2 - RADIATOR
3 - AIR DAM
4 - A/C CONDENSER
5 - AIR SEAL
WJENGINE 7 - 43
RADIATOR - 4.7L (Continued)

the radiator to flush the radiator and/or A/C con-
denser of debris.
INSPECTION
The radiator cooling fins should be checked for
damage or deterioration. Inspect cooling fins to make
sure they are not bent or crushed, these areas result
in reduced heat exchange causing the cooling system
to operate at higher temperatures. Inspect the plastic
end tanks for cracks, damage or leaks.
Inspect the radiator neck for damage or distortion.
INSTALLATION
CAUTION: Before installing the radiator or A/C con-
denser, be sure the radiator-to-body and radiator-to-
A/C condenser rubber air seals (Fig. 39) are
properly fastened to their original positions. These
are used at the top, bottom and sides of the radia-
tor and A/C condenser. To prevent overheating,
these seals must be installed to their original posi-
tions.
(1) Equipped with air conditioning: Gently lower
the radiator and fan shroud into the vehicle. Guide
the two radiator alignment dowels through the holes
in the rubber air seals first and then through the A/C
support brackets (Fig. 40). Continue to guide thealignment dowels into the rubber grommets located
in lower radiator crossmember. The holes in the
L-shaped brackets (located on bottom of A/C con-
denser) must be positioned between bottom of rubber
air seals and top of rubber grommets.
(2) Connect the radiator upper and lower hoses
and hose clamps to radiator.
CAUTION: The tangs on the hose clamps must be
positioned straight down.
(3) Install coolant reserve/overflow tank hose at
radiator.
(4) Connect both transmission cooler lines at the
radiator.
(5) Install both radiator mounting bolts.
(6) Install air inlet duct at grill.
(7) Attach electric connector for hydraulic fan con-
trol solenoid.
(8) Install the grill (Refer to 23 - BODY/EXTERI-
OR/GRILLE - INSTALLATION).
(9) Connect the two high pressure lines to the
hydraulic fan drive. Tighten
1¤2in. pressure line fit-
ting to 49 N´m (36 ft. lbs.). and the 3/8 in. pressure
line fitting to 29 N´m (21.5 ft. lbs.).
(10) Connect the low pressure hose to the hydrau-
lic fan drive. Position the spring clamp.
(11) Connect the power steering filter hoses to the
filter. Install new hose clamps.
(12) Rotate the fan blades (by hand) and check for
interference at fan shroud.
(13) Refill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(14) Refill the power steering reservoir and bleed
air from system (Refer to 19 - STEERING/PUMP -
STANDARD PROCEDURE).
(15) Connect battery cable at battery.
(16) Start and warm engine. Check for leaks.
RADIATOR - 4.0L
DESCRIPTION
All vehicles are equipped with a cross flow type
radiator with plastic side tanks (Fig. 36).
Plastic tanks, while stronger than brass, are sub-
ject to damage by impact, such as from tools or
wrenches. Handle radiator with care.
REMOVAL
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM COOLANT
CAN OCCUR. REFER TO COOLING SYSTEM DRAIN-
ING.
Fig. 35 Radiator Alignment Dowels - Typical
1 - RADIATOR
2 - ALIGNMENT DOWEL
3 - RADIATOR LOWER ISOLATOR
4 - RADIATOR LOWER CROSSMEMBER
7 - 44 ENGINEWJ
RADIATOR - 4.7L (Continued)

INSPECTION
The radiator cooling fins should be checked for
damage or deterioration. Inspect cooling fins to make
sure they are not bent or crushed, these areas result
in reduced heat exchange causing the cooling system
to operate at higher temperatures. Inspect the plastic
end tanks for cracks, damage or leaks.
Inspect the radiator neck for damage or distortion.
INSTALLATION
CAUTION: Before installing the radiator or A/C con-
denser, be sure the radiator-to-body and radiator-to-
A/C condenser rubber air seals (Fig. 39) are
properly fastened to their original positions. These
are used at the top, bottom and sides of the radia-
tor and A/C condenser. To prevent overheating,
these seals must be installed to their original posi-
tions.
(1) Equipped with air conditioning: Gently lower
the radiator into the vehicle. Guide the two radiator
alignment dowels through the holes in the rubber air
seals first and then through the A/C support brackets
(Fig. 40). Continue to guide the alignment dowels
into the rubber grommets located in lower radiator
crossmember. The holes in the L-shaped brackets
(located on bottom of A/C condenser) must be posi-
tioned between bottom of rubber air seals and top of
rubber grommets.
(2) Connect the radiator upper and lower hoses
and hose clamps to radiator (Fig. 41).
CAUTION: The tangs on the hose clamps must be
positioned straight down.
(3) Install coolant reserve/overflow tank hose at
radiator (Fig. 41).
(4) Connect both transmission cooler lines at the
radiator (Fig. 41).
(5) Install both radiator mounting bolts (Fig. 41).
(6) Install air inlet duct at grill.
(7) Attach electric fan harness to shroud, then con-
nect harness to connector (Fig. 41).
(8) Install the grill (Refer to 23 - BODY/EXTERI-
OR/GRILLE - INSTALLATION).
(9) Install the fan/viscous fan drive assembly to
the water pump.
(10) Rotate the fan blades (by hand) and check for
interference at fan shroud.
(11) Be sure of at least 25 mm (1.0 inch) between
tips of fan blades and fan shroud.
(12) Fill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(13) Connect battery cable at battery.
(14) Start and warm engine. Check for leaks.
RADIATOR FAN MOTOR
DIAGNOSIS AND TESTINGÐELECTRIC
COOLING FAN
The powertrain control module (PCM) will enter a
diagnostic trouble code (DTC) in memory if it detects
a problem in the auxiliary cooling fan relay or circuit.
(Refer to 25 - EMISSIONS CONTROL - DESCRIP-
TION).
If the electric cooling fan is inoperative, check the
15A fuse in the junction block and the 40A fuse in
the Power Distribution Center (PDC) with a 12 volt
test lamp or DVOM. Refer to the inside of the PDC
cover for the exact location of the fuse. If fuses are
okay, refer to ELECTRICAL for cooling fan and relay
circuit schematic.
WATER PUMP - 4.7L
DESCRIPTION
DESCRIPTIONÐWATER PUMP
A centrifugal water pump circulates coolant
through the water jackets, passages, intake manifold,
radiator core, cooling system hoses and heater core.
The pump is driven from the engine crankshaft by a
single serpentine drive belt.
The water pump impeller is pressed onto the rear
of a shaft that rotates in bearings pressed into the
housing. The housing has two small holes to allow
seepage to escape. The water pump seals are lubri-
cated by the antifreeze in the coolant mixture. No
additional lubrication is necessary.
Both heater hoses are connected to fittings on the
timing chain front cover. The water pump is also
mounted directly to the timing chain cover and is
equipped with a non serviceable integral pulley (Fig.
42).
DESCRIPTIONÐWATER PUMP BYPASS
The 4.7L engine uses an internal water/coolant
bypass system. The design uses galleries in the tim-
ing chain cover to circulate coolant during engine
warm-up preventing the coolant from flowing
through the radiator. The thermostat uses a stub
shaft located at the rear of the thermostat (Fig. 43)
to control flow through the bypass gallery.
OPERATION
OPERATIONÐWATER PUMP
A centrifugal water pump circulates coolant
through the water jackets, passages, intake manifold,
WJENGINE 7 - 47
RADIATOR - 4.0L (Continued)

TRANSMISSION
TABLE OF CONTENTS
page page
TRANS COOLER
DESCRIPTION.........................55STANDARD PROCEDURE - FLUSHING
COOLERS AND TUBES.................55
TRANS COOLER
DESCRIPTION
An internal high capacity/high efficiency cooler is
used on all vehicles these coolers are an oil-to-coolant
type which consists of plates mounted in the radiator
outlet tank (Fig. 36). Because the internal oil cooler
is so efficient, no auxiliary oil cooler is offered The
cooler is not servicable seperatly from the radiator.
STANDARD PROCEDURE - FLUSHING
COOLERS AND TUBES
When a transmission failure has contaminated the
fluid, the oil cooler(s) must be flushed. The torque
converter must also be replaced. This will insure that
metal particles or sludged oil are not later trans-
ferred back into the reconditioned (or replaced) trans-
mission.
The only recommended procedure for flushing cool-
ers and lines is to use Tool 6906-B Cooler Flusher.
WARNING: WEAR PROTECTIVE EYEWEAR THAT
MEETS THE REQUIREMENTS OF OSHA AND ANSI
Z87.1±1968. WEAR STANDARD INDUSTRIAL RUB-
BER GLOVES.
KEEP LIGHTED CIGARETTES, SPARKS, FLAMES,
AND OTHER IGNITION SOURCES AWAY FROM THE
AREA TO PREVENT THE IGNITION OF COMBUSTI-
BLE LIQUIDS AND GASES. KEEP A CLASS (B) FIRE
EXTINGUISHER IN THE AREA WHERE THE
FLUSHER WILL BE USED.
KEEP THE AREA WELL VENTILATED.
DO NOT LET FLUSHING SOLVENT COME IN CON-
TACT WITH YOUR EYES OR SKIN: IF EYE CONTAM-
INATION OCCURS, FLUSH EYES WITH WATER FOR
15 TO 20 SECONDS. REMOVE CONTAMINATED
CLOTHING AND WASH AFFECTED SKIN WITH
SOAP AND WATER. SEEK MEDICAL ATTENTION.
(1) Remove cover plate filler plug on Tool 6906-B.
Fill reservoir 1/2 to 3/4 full of fresh flushing solution.
Flushing solvents are petroleum based solutions gen-
erally used to clean automatic transmission compo-
nents.DO NOTuse solvents containing acids, water,
gasoline, or any other corrosive liquids.(2) Reinstall filler plug on Tool 6906-B.
(3) Verify pump power switch is turned OFF. Con-
nect red alligator clip to positive (+) battery post.
Connect black (-) alligator clip to a good ground.
(4) Disconnect the cooler lines at the transmission.
NOTE: When flushing transmission cooler and
lines, ALWAYS reverse flush.
NOTE: The converter drainback valve must be
removed and an appropriate replacement hose
installed to bridge the space between the transmis-
sion cooler line and the cooler fitting. Failure to
remove the drainback valve will prevent reverse
flushing the system. A suitable replacement hose
can be found in the adapter kit supplied with the
flushing tool.
(5) Connect the BLUE pressure line to the OUT-
LET (From) cooler line.
(6) Connect the CLEAR return line to the INLET
(To) cooler line
(7) Turn pump ON for two to three minutes to
flush cooler(s) and lines.
(8) Turn pump OFF.
(9) Disconnect CLEAR suction line from reservoir
at cover plate. Disconnect CLEAR return line at
cover plate, and place it in a drain pan.
(10) Turn pump ON for 30 seconds to purge flush-
ing solution from cooler and lines. Turn pump OFF.
(11) Place CLEAR suction line into a one quart
container of MopartATF +4, type 9602, Automatic
Transmission Fluid.
(12) Turn pump ON until all transmission fluid is
removed from the one quart container and lines. This
purges any residual cleaning solvent from the trans-
mission cooler and lines. Turn pump OFF.
(13) Disconnect alligator clips from battery. Recon-
nect flusher lines to cover plate, and remove flushing
adapters from cooler lines.
WJTRANSMISSION 7 - 55

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

AUDIO SYSTEM DIAGNOSIS
CONDITION POSSIBLE CAUSES CORRECTION
NO AUDIO 1. Fuse faulty. 1. Check radio fuse in Junction Block (JB) and
Ignition-Off Draw (IOD) fuse in Power Distribution
Center (PDC). Replace fuses, if required.
2. Radio connector faulty. 2. Check for loose or corroded radio connector.
Repair, if required.
3. Wiring faulty. 3. Check for battery voltage at radio connector.
Repair wiring, if required.
4. Radio ground faulty. 4. Check for continuity between radio chassis and
a known good ground. There should be
continuity. Repair ground, if required.
5. Radio faulty. 5. (Refer to 8 - ELECTRICAL/AUDIO/RADIO -
DIAGNOSIS AND TESTING).
6. Speakers faulty. 6. (Refer to 8 - ELECTRICAL/AUDIO/SPEAKER -
DIAGNOSIS AND TESTING).
7. Amplifier faulty (if
equipped).7. (Refer to 8 - ELECTRICAL/AUDIO/AMPLIFIER
- DIAGNOSIS AND TESTING).
NO RADIO DISPLAY 1. Fuse faulty. 1. Check radio fuse in Junction Block (JB) and
Ignition-Off Draw (IOD) fuse in Power Distribution
Center (PDC). Replace fuses, if required.
2. Radio connector faulty. 2. Check for loose or corroded radio connector.
Repair, if required.
3. Wiring faulty. 3. Check for battery voltage at radio connector.
Repair wiring, if required.
4. Radio ground faulty. 4. Check for continuity between radio chassis and
a known good ground. There should be
continuity. Repair ground, if required.
5. Radio faulty. 5. (Refer to 8 - ELECTRICAL/AUDIO/RADIO -
DIAGNOSIS AND TESTING).
CLOCK WILL NOT KEEP
SET TIME1. Fuse faulty. 1. Check Ignition-Off Draw (IOD) fuse in the
Power Distribution Center (PDC). Replace fuse, if
required.
2. Radio connector faulty. 2. Check for loose or corroded radio connector.
Repair, if required.
3. Wiring faulty. 3. Check for battery voltage at radio connector.
Repair wiring, if required.
4. Radio ground faulty. 4. Check for continuity between radio chassis and
a known good ground. There should be
continuity. Repair ground, if required.
5. Radio faulty. 5. (Refer to 8 - ELECTRICAL/AUDIO/RADIO -
DIAGNOSIS AND TESTING).
8A - 4 AUDIOWJ
AUDIO (Continued)