2003 JEEP GRAND CHEROKEE 23 Body

CATALYTIC CONVERTER - 4.7L
DESCRIPTION - CATALYTIC CONVERTER
WARNING: THE NORMAL OPERATING TEMPERA-
TURE OF THE EXHAUST SYSTEM IS VERY HIGH.
THEREFORE, NEVER WORK AROUND OR ATTEMPT
TO SERVICE ANY PART OF THE EXHAUST SYSTEM
UNTIL IT IS COOLED. SPECIAL CARE SHOULD BE
TAKEN WHEN WORKING NEAR THE CATALYTIC
CONVERTER. THE TEMPERATURE OF THE CON-
VERTER RISES TO A HIGH LEVEL AFTER A SHORT
PERIOD OF ENGINE OPERATION TIME.
CAUTION: DO NOT remove spark plug wires from
plugs or by any other means short out cylinders.
Failure of the catalytic converter can occur due to a
temperature increase caused by unburned fuel
passing through the converter.The stainless steel catalytic converter body is
designed to last the life of the vehicle. Excessive heat
can result in bulging or other distortion, but exces-
sive heat will not be the fault of the converter. If
unburned fuel enters the converter, overheating may
occur. If a converter is heat-damaged, correct the
cause of the damage at the same time the converter
is replaced. Also, inspect all other components of the
exhaust system for heat damage.
Unleaded gasoline must be used to avoid con-
taminating the catalyst core.
50 State emission vehicles incorporate two mini
catalytic converters located after the exhaust mani-
folds and before the inline catalytic converter (Fig. 6).
REMOVAL
WARNING: IF TORCHES ARE USED WHEN WORK-
ING ON THE EXHAUST SYSTEM, DO NOT ALLOW
THE FLAME NEAR THE FUEL LINES.
Fig. 6 4.7L Catalytic Converter and O2 Sensor Configuration - 50 State Emissions
11 - 6 EXHAUST SYSTEMWJ

(1) Raise and support the vehicle.
(2) Saturate the bolts and nuts with heat valve
lubricant. Allow 5 minutes for penetration.
(3) Remove nuts from the catalytic converter and
exhaust pipe flange connection (Fig. 7).
(4) Loosen exhaust clamp from the catalytic con-
verter and muffler connection (Fig. 7).
(5) Disconnect oxygen sensor wiring (Fig. 7).
(6) Heat the catalytic converter to muffler connec-
tion with a torch until the metal becomes cherry red.
(7) While the metal is still cherry red, twist the
catalytic converter back and forth to separate it from
the muffler (Fig. 8).
INSPECTION
Look at the stainless steel body of the converter,
inspect for bulging or other distortion that could be a
result of overheating. If the converter has a heat
shield attached make sure it is not bent or loose.
If you suspect internal damage to the catalyst, tap-
ping the bottom of the catalyst with a rubber mallet
may indicate a damaged core.
INSTALLATION
(1) Position the catalytic converter onto the
exhaust pipe flange connection (Fig. 7). Tighten the
nuts to 28 N´m (250 in. lbs.) torque.
(2) Install the muffler onto the catalytic converter
until the alignment tab is inserted into the align-
ment slot.
(3) Install the exhaust clamp at the muffler and
catalytic converter connection (Fig. 7). Tighten the
clamp nuts to 47 N´m (35 ft. lbs.) torque.
(4) Connect oxygen sensor wiring (Fig. 7).
(5) Lower the vehicle.
(6) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels.
Adjust the alignment, if needed.
Fig. 7 Exhaust Pipe-to-Catalytic Converter-to-Muffler
Connection
1 - EXHAUST CLAMP ASSEMBLY
2 - OXYGEN SENSOR
3 - MUFFLER
4 - CATALYTIC CONVERTER
5 - EXHAUST PIPE WITH FLANGE JOINT
6 - NUTS (3)
Fig. 8 Catalytic ConverterÐRemoval
1 - EXHAUST PIPE WITH FLANGE
2 - NUTS (3)
3 - CATALYTIC CONVERTER
WJEXHAUST SYSTEM 11 - 7
CATALYTIC CONVERTER - 4.7L (Continued)

NOTE: When servicing the exhaust system, replace
the factory installed uni-clamp with standard u-bolt
clamps.
(2) Position the catalytic converter onto the
exhaust pipe flange connection. Tighten retaining
nuts to 28 N´m (250 in. lbs.) (Fig. 12).
(3) Coat the oxygen sensor with anti-seize com-
pound. Install the sensor and tighten the nut to 48
N´m (35 ft. lbs.) torque (Fig. 9).
(4) Lower the vehicle.
(5) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels.
Adjust the alignment, if needed.
(6) After initial start-up, check the engine exhaust
manifold to exhaust pipe nuts for proper torque.
Fig. 10 Catalytic ConverterÐRemoval
1 - EXHAUST PIPE WITH FLANGE
2 - NUTS (3)
3 - CATALYTIC CONVERTER
Fig. 11 Exhaust Pipe 4.0L
1 - NUT
2 - EXHAUST MANIFOLD
3 - TRANSMISSION SUPPORT
4 - EXHAUST PIPE
5 - MINI CATALYTIC CONVERTER
6 - BOLT
Fig. 12 Installing Exhaust Clamps
1 - CATALYTIC CONVERTER
2 - MUFFLER
WJEXHAUST SYSTEM 11 - 9
EXHAUST PIPE - 4.0L (Continued)

NOTE: When servicing the exhaust system, replace
the factory installed uni-clamp with standard u-bolt
clamps.
(2) Position the catalytic converter onto the
exhaust pipe flange connection. Tighten retaining
nuts to 28 N´m (250 in. lbs.). (Fig. 16)
(3) Coat the oxygen sensor with anti-seize com-
pound. Install the sensor and tighten the nut to 48
N´m (35 ft. lbs.) torque (Fig. 13).
(4) Lower the vehicle.
(5) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels.
Adjust the alignment, if needed.
(6) After initial start-up, check the engine exhaust
manifold to exhaust pipe nuts for proper torque.
Fig. 14 Catalytic ConverterÐRemoval
1 - EXHAUST PIPE WITH FLANGE
2 - NUTS (3)
3 - CATALYTIC CONVERTER
Fig. 15 Exhaust Pipe 4.7L
1 - EXHAUST PIPE HANGER
A - NUTS (4)
3 - EXHAUST PIPE
B - BOLTS (4)
Fig. 16 Installing Exhaust Clamps
1 - CATALYTIC CONVERTER
2 - MUFFLER
WJEXHAUST SYSTEM 11 - 11
EXHAUST PIPE - 4.7L (Continued)

HEAT SHIELDS
DESCRIPTION
Heat shields are needed to protect both the vehicle
and the environment from the high temperatures
developed by the catalytic converter. The catalytic
converter releases additional heat into the exhaust
system. Under severe operating conditions, the tem-
perature increases in the area of the converter. Such
conditions can exist when the engine misfires or oth-
erwise does not operate at peak efficiency (Fig. 17).
MUFFLER
DESCRIPTION
Both the 4.0L and 4.7L engines use a stainless
steel muffler to control exhaust noise levels and
exhaust back pressure. The muffler and tailpipe are
a one piece assembly (Fig. 18).
REMOVAL
All original equipment exhaust systems are manu-
factured with the tailpipe welded to the muffler. Ser-
vice replacement mufflers and tailpipes are either
clamped together or welded together.
WARNING: IF TORCHES ARE USED WHEN WORK-
ING ON THE EXHAUST SYSTEM, DO NOT ALLOW
THE FLAME NEAR THE FUEL LINES.
(1) Raise and support the vehicle.
(2) Saturate the bolts and nuts with heat valve
lubricant. Allow 5 minutes for penetration.(3) Loosen the exhaust clamp on the catalytic con-
verter to muffler connection (Fig. 19).
(4) Heat the catalytic converter-to-muffler connec-
tion with a torch until the metal becomes cherry red.
(5) While the metal is still cherry red, remove the
tailpipe/muffler assembly from the catalytic con-
verter.
(6) Remove the tailpipe from the tailpipe hanger
(Fig. 20).
(7) Remove the tailpipe/muffler assembly (Fig. 20).
INSTALLATION
(1) If the tailpipe hanger assembly was removed,
install the hanger to the frame. Tighten the bolts to
22 N´m (192 in. lbs.) torque.
(2) Position the tailpipe and muffler onto the
tailpipe hanger (Fig. 20) .
(3) Install the muffler onto the catalytic converter.
Make sure that the tailpipe has sufficient clearance
from the floor pan. Install exhaust clamp and tighten
the nuts to 47 N´m (35 ft. lbs.) torque (Fig. 19) .
(4) Lower the vehicle.
(5) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels.
Adjust the alignment, if needed.
Fig. 17 Front and Rear Floor Pan Heat Shields
Typical
1 - REAR FLOOR PAN HEAT SHIELD
2 - HEAT SHIELD RETAINING NUTS (QTY 8)
3 - FRONT FLOOR PAN HEAT SHIELD
Fig. 18 Muffler and Tailpipe
1 - CATALYTIC CONVERTER
2 - TAILPIPE HANGER
3 - TAILPIPE
4 - MUFFLER
11 - 12 EXHAUST SYSTEMWJ

REAR ABSORBER
REMOVAL
(1) Remove rear fascia, refer to (Refer to 13 -
FRAMES & BUMPERS/BUMPERS/REAR FASCIA -
REMOVAL).
(2) Remove rivets attaching absorber to rear cross-
member (Fig. 5).
(3) Separate absorber from vehicle.
INSTALLATION
(1) Position absorber on vehicle.
(2) Install rivets attaching absorber to rear cross-
member (Fig. 2).
(3) Install rear fascia, refer to (Refer to 13 -
FRAMES & BUMPERS/BUMPERS/REAR FASCIA -
INSTALLATION).
REAR FASCIA
REMOVAL
(1) Raise and support vehicle.
(2) Remove wheels.
(3) Remove plastic push pins attaching fascia to
fuel tank skid plate.
(4) Remove plastic rivets attaching fascia to wheel
liner.
Fig. 1 Front Fascia
1 - BODY
2 - FASCIA
Fig. 2 Front Fascia
1 - WHEEL LINER
2 - FASCIA
3 - FOG LAMP CONNECTOR
4 - PLASTIC PUSH PIN
5 - PLASTIC RIVET
Fig. 3 Front Fascia
1 - SCREW
2 - FASCIA
13 - 2 FRAME & BUMPERSWJ
FRONT FASCIA (Continued)

(5) Remove nuts attaching upper edge of fascia to
quarter panel and wheel liner (Fig. 4).
(6) Remove plastic push pins attaching fascia to
liftgate opening (Fig. 5).
(7) Remove screws attaching fascia to liftgate
opening.
(8) Remove D pillar trim and scuff plate outboard
screws.
(9) Remove the rearward tie down screws and the
aperture trim panel.
(10) Carefully peel back the rubber body sealer
patch to access the retainer clips.
(11) Release the forward and rearward retainer
clips on both sides of the fascia.
(12) Grasp forward edges of fascia and pull out-
ward to disengage retainers attaching fascia to quar-
ter panel (Fig. 6).
(13) Separate fascia from vehicle.
Fig. 5 Rear Fascia
1 - ABSORBER
2 - RIVET3 - FASCIA
4 - PLASTIC PUSH PIN
Fig. 4 Rear Fascia Attachment
1 - FASCIA
2 - PLASTIC PUSH PIN
WJFRAME & BUMPERS 13 - 3
REAR FASCIA (Continued)

STANDARD PROCEDURE - FUEL SYSTEM
PRESSURE RELEASE
Use following procedure if the fuel injector
rail is, or is not equipped with a fuel pressure
test port.
(1) Remove fuel fill cap.
(2) Remove fuel pump relay from Power Distribu-
tion Center (PDC). For location of relay, refer to label
on underside of PDC cover.
(3) Start and run engine until it stalls.
(4) Attempt restarting engine until it will no
longer run.
(5) Turn ignition key to OFF position.
CAUTION: Steps 1, 2, 3 and 4 must be performed to
relieve high pressure fuel from within fuel rail. Do
not attempt to use following steps to relieve this
pressure as excessive fuel will be forced into a cyl-
inder chamber.
(6) Unplug connector from any fuel injector.
(7) Attach one end of a jumper wire with alligator
clips (18 gauge or smaller) to either injector terminal.(8) Connect other end of jumper wire to positive
side of battery.
(9) Connect one end of a second jumper wire to
remaining injector terminal.
CAUTION: Powering an injector for more than a few
seconds will permanently damage the injector.
(10) Momentarily touch other end of jumper wire
to negative terminal of battery for no more than a
few seconds.
(11) Place a rag or towel below fuel line quick-con-
nect fitting at fuel rail.
(12) Disconnect quick-connect fitting at fuel rail.
Refer to Quick-Connect Fittings.
(13) Return fuel pump relay to PDC.
(14) One or more Diagnostic Trouble Codes (DTC's)
may have been stored in PCM memory due to fuel
pump relay removal. The DRBtscan tool must be
used to erase a DTC.
SPECIFICATIONS
FUEL SYSTEM PRESSURE
339 kPa   34 kPa (49.2 psi   5 psi).
TORQUE - FUEL DELIVERY
DESCRIPTION N-m Ft. Lbs. In. Lbs.
Accelerator Pedal Bracket Mounting Nuts
(without adjustable pedals)12  2 - 105  20
Fuel Filter/Fuel Press. Reg. Bolts 3 - 26
Fuel Hose Clamps 3 - 26
Fuel Injector Rail Mounting Bolts -4.0L Engine 11 - 100
Fuel Injector Rail Mounting Bolts -4.7L V-8
Engine11 - 100
Fuel Pump Module Locknut 74 55 -
Fuel Tank Filler Tube-to-Body Mounting Bolts 2 - 15
Fuel Tank-to-Body Mounting Bolts 88 65 -
Fuel Tank Support Bracket Bolts (large brackets) 88 65 -
Fuel Tank Support Bracket Bolts (small bracket) 5 - 45
Fuel Tank Support Bracket Nuts (large brackets) 61 45 -
Fuel Tank Heat Shield Nuts (shield-to-tank) 9 - 85
Fuel Tank Heat Shield Nuts (shield-to-body) 3 - 25
14 - 4 FUEL DELIVERYWJ
FUEL DELIVERY (Continued)