2003 JEEP GRAND CHEROKEE Battery

The PCM determines injector on-time (pulse width)
based on various inputs.
DIAGNOSIS AND TESTING - FUEL INJECTOR
To perform a complete test of the fuel injectors and
their circuitry, use the DRB scan tool and refer to the
appropriate Powertrain Diagnostics Procedures man-
ual. To test the injector only, refer to the following:
Disconnect the fuel injector wire harness connector
from the injector. The injector is equipped with 2
electrical terminals (pins). Place an ohmmeter across
the terminals. Resistance reading should be approxi-
mately 12 ohms  1.2 ohms at 20ÉC (68ÉF).
REMOVAL
WARNING: THE FUEL SYSTEM IS UNDER CON-
STANT PRESSURE EVEN WITH ENGINE OFF.
BEFORE SERVICING FUEL INJECTOR(S), FUEL
SYSTEM PRESSURE MUST BE RELEASED.
To remove one or more fuel injectors, the fuel rail
assembly must be removed from engine.
(1) Perform Fuel System Pressure Release Proce-
dure.
(2) Remove fuel injector rail. Refer to Fuel Injector
Rail Removal/Installation.
(3) Remove clip(s) retaining injector(s) to fuel rail
(Fig. 25).
(4) Remove injector(s) from fuel rail.
INSTALLATION
(1) Apply a small amount of engine oil to each fuel
injector o-ring. This will help in fuel rail installation.
(2) Install injector(s) and injector clip(s) to fuel
rail.
(3) Install fuel rail assembly. Refer to Fuel Injector
Rail Removal/Installation.
(4) Start engine and check for leaks.
FUEL PUMP RELAY
DESCRIPTION
The 5±pin, 12±volt, fuel pump relay is located in
the Power Distribution Center (PDC). Refer to the
label on the PDC cover for relay location.
OPERATION
The Powertrain Control Module (PCM) energizes
the electric fuel pump through the fuel pump relay.
The fuel pump relay is energized by first applying
battery voltage to it when the ignition key is turned
ON, and then applying a ground signal to the relay
from the PCM.
Whenever the ignition key is turned ON, the elec-
tric fuel pump will operate. But, the PCM will shut-
down the ground circuit to the fuel pump relay in
approximately 1±3 seconds unless the engine is oper-
ating or the starter motor is engaged.
IDLE AIR CONTROL MOTOR
DESCRIPTION
The IAC stepper motor is mounted to the throttle
body, and regulates the amount of air bypassing the
control of the throttle plate. As engine loads and
ambient temperatures change, engine rpm changes.
A pintle on the IAC stepper motor protrudes into a
passage in the throttle body, controlling air flow
through the passage. The IAC is controlled by the
Powertrain Control Module (PCM) to maintain the
target engine idle speed.
OPERATION
At idle, engine speed can be increased by retract-
ing the IAC motor pintle and allowing more air to
pass through the port, or it can be decreased by
restricting the passage with the pintle and diminish-
ing the amount of air bypassing the throttle plate.
The IAC is called a stepper motor because it is
moved (rotated) in steps, or increments. Opening the
IAC opens an air passage around the throttle blade
which increases RPM.Fig. 25 Fuel Injector MountingÐTypical (4.7L V-8
Engine Shown)
1 - INLET FITTING
2 - FUEL INJECTOR RAIL
3 - CLIP
4 - FUEL INJECTOR
14 - 44 FUEL INJECTIONWJ
FUEL INJECTOR (Continued)

The other two heater elements (downstream sen-
sors 1/2 and 2/2) are controlled by the downstream
heater relay through output signals from the PCM.
To avoid a large simultaneous current surge, power
is delayed to the 2 downstream heater elements by
the PCM for approximately 2 seconds.
REMOVAL
(1) Remove PDC cover.
(2) Remove relay from PDC.
(3) Check condition of relay terminals and PDC
connector terminals for damage or corrosion. Repair
if necessary before installing relay.
(4) Check for pin height (pin height should be the
same for all terminals within the PDC connector).
Repair if necessary before installing relay.
INSTALLATION
(1) Install relay to PDC.
(2) Install cover to PDC.
O2S SENSOR
DESCRIPTION
The Oxygen Sensors (O2S) are attached to, and
protrude into the vehicle exhaust system. Depending
on the emission package, the vehicle may use a total
of either 2 or 4 sensors.
Federal Emissions Package:Two sensors are
used: upstream (referred to as 1/1) and downstream
(referred to as 1/2). With this emission package, the
upstream sensor (1/1) is located just before the main
catalytic convertor. The downstream sensor (1/2) is
located just after the main catalytic convertor.
4.7L V-8 With California Emissions Package:
On this emissions package, 4 sensors are used: 2
upstream (referred to as 1/1 and 2/1) and 2 down-
stream (referred to as 1/2 and 2/2). With this emis-
sion package, the right upstream sensor (2/1) is
located in the right exhaust downpipe just before the
mini-catalytic convertor. The left upstream sensor
(1/1) is located in the left exhaust downpipe just
before the mini-catalytic convertor. The right down-
stream sensor (2/2) is located in the right exhaust
downpipe just after the mini-catalytic convertor, and
before the main catalytic convertor. The left down-
stream sensor (1/2) is located in the left exhaust
downpipe just after the mini-catalytic convertor, and
before the main catalytic convertor.
4.0L 6±Cylinder With California Emissions
Package:On this emissions package, 4 sensors are
used: 2 upstream (referred to as 1/1 and 2/1) and 2
downstream (referred to as 1/2 and 2/2). With this
emission package, the rear/upper upstream sensor
(2/1) is located in the exhaust downpipe just beforethe rear mini-catalytic convertor. The front/upper
upstream sensor (1/1) is located in the exhaust down-
pipe just before the front mini-catalytic convertor.
The rear/lower downstream sensor (2/2) is located in
the exhaust downpipe just after the rear mini-cata-
lytic convertor, and before the main catalytic conver-
tor. The front/lower downstream sensor (1/2) is
located in the exhaust downpipe just after the front
mini-catalytic convertor, and before the main cata-
lytic convertor.
OPERATION
An O2 sensor is a galvanic battery that provides
the PCM with a voltage signal (0-1 volt) inversely
proportional to the amount of oxygen in the exhaust.
In other words, if the oxygen content is low, the volt-
age output is high; if the oxygen content is high the
output voltage is low. The PCM uses this information
to adjust injector pulse-width to achieve the
14.7±to±1 air/fuel ratio necessary for proper engine
operation and to control emissions.
The O2 sensor must have a source of oxygen from
outside of the exhaust stream for comparison. Cur-
rent O2 sensors receive their fresh oxygen (outside
air) supply through the O2 sensor case housing.
Four wires (circuits) are used on each O2 sensor: a
12±volt feed circuit for the sensor heating element; a
ground circuit for the heater element; a low-noise
sensor return circuit to the PCM, and an input cir-
cuit from the sensor back to the PCM to detect sen-
sor operation.
Oxygen Sensor Heaters/Heater Relays:
Depending on the emissions package, the heating ele-
ments within the sensors will be supplied voltage
from either the ASD relay, or 2 separate oxygen sen-
sor relays. Refer to Wiring Diagrams to determine
which relays are used.
The O2 sensor uses a Positive Thermal Co-efficient
(PTC) heater element. As temperature increases,
resistance increases. At ambient temperatures
around 70ÉF, the resistance of the heating element is
approximately 4.5 ohms on 4.0L engines. It is
approximately 13.5 ohms on the 4.7L engine. As the
sensor's temperature increases, resistance in the
heater element increases. This allows the heater to
maintain the optimum operating temperature of
approximately 930É-1100ÉF (500É-600É C). Although
the sensors operate the same, there are physical dif-
ferences, due to the environment that they operate
in, that keep them from being interchangeable.
Maintaining correct sensor temperature at all
times allows the system to enter into closed loop
operation sooner. Also, it allows the system to remain
in closed loop operation during periods of extended
idle.
14 - 50 FUEL INJECTIONWJ
O2S HEATER RELAY (Continued)

COLUMN
TABLE OF CONTENTS
page page
COLUMN
DESCRIPTION
SERVICE WARNINGS AND CAUTIONS......7
REMOVAL.............................8
INSTALLATION.........................11
SPECIFICATIONS
TORQUE CHART......................12
SPECIAL TOOLS
STEERING COLUMN...................12
IGNITION SWITCH
DESCRIPTION.........................12
DIAGNOSIS AND TESTING - IGNITION
SWITCH............................12
REMOVAL
IGNITION SWITCH REMOVAL............13INSTALLATION
IGNITION SWITCH INSTALLATION........13
KEY-IN IGNITION SWITCH
DESCRIPTION.........................14
OPERATION...........................14
DIAGNOSIS AND TESTING
KEY-IN IGNITION SWITCH..............14
LOCK CYLINDER
REMOVAL.............................14
INSTALLATION.........................15
STEERING WHEEL
REMOVAL.............................15
INSTALLATION.........................15
COLUMN
DESCRIPTION
SERVICE WARNINGS AND CAUTIONS
DESCRIPTION
The tilt column (Fig. 1) has been designed to be
serviced as an assembly, less the wiring, switches,
shrouds, steering wheel, etc. Most steering column
components can be serviced without removing the
steering column from the vehicle.To service the steering wheel, switches or air-
bag,(Refer to 8 - ELECTRICAL/RESTRAINTS -
WARNING).
WARNING: THE AIRBAG SYSTEM IS A SENSITIVE,
COMPLEX ELECTRO-MECHANICAL UNIT. BEFORE
ATTEMPTING TO DIAGNOSE, REMOVE OR INSTALL
THE AIRBAG SYSTEM COMPONENTS YOU MUST
FIRST DISCONNECT AND ISOLATE THE BATTERY
NEGATIVE (GROUND) CABLE. THEN WAIT TWO
MINUTES FOR THE SYSTEM CAPACITOR TO DIS-
CHARGE. FAILURE TO DO SO COULD RESULT IN
ACCIDENTAL DEPLOYMENT OF THE AIRBAG AND
POSSIBLE PERSONAL INJURY. THE FASTENERS,
SCREWS, AND BOLTS, ORIGINALLY USED FOR
THE AIRBAG COMPONENTS, HAVE SPECIAL COAT-
INGS AND ARE SPECIFICALLY DESIGNED FOR THE
AIRBAG SYSTEM. THEY MUST NEVER BE
REPLACED WITH ANY SUBSTITUTES. ANYTIME A
NEW FASTENER IS NEEDED, REPLACE WITH THE
CORRECT FASTENERS PROVIDED IN THE SERVICE
PACKAGE OR FASTENERS LISTED IN THE PARTS
BOOKS.
CAUTION: Safety goggles should be worn at all
times when working on steering columns.
Fig. 1 Steering Column
WJCOLUMN 19 - 7

REMOVAL
WARNING: BEFORE SERVICING THE STEERING
COLUMN THE AIRBAG SYSTEM MUST BE DIS-
ARMED. FAILURE TO DO SO MAY RESULT IN ACCI-
DENTAL DEPLOYMENT OF THE AIRBAG AND
POSSIBLE PERSONAL INJURY.(Refer to 8 - ELEC-
TRICAL/RESTRAINTS/DRIVER AIRBAG - REMOVAL).
(1) Position front wheels straight ahead.
(2) Disconnect and isolate the negative (ground)
cable from the battery.
(3) Remove the airbag,(Refer to 8 - ELECTRICAL/
RESTRAINTS/DRIVER AIRBAG - REMOVAL).
(4) Remove the steering wheel nut and remove
wheel with Puller C-3894-A (Fig. 2).
NOTE: Ensure the puller jaws are seated in the
pockets (Fig. 3) of the steering wheel armature.(5) Remove the cluster bezel by pulling it from the
instrument panel (Fig. 4).
Fig. 2 Steering Wheel Puller
1 - PULLER
2 - STEERING WHEEL
Fig. 3 Steering Wheel Pockets
1 - STEERING WHEEL POCKETS
Fig. 4 Cluster Bezel
1 - CLUSTER
2 - CLUSTER BEZEL
3 - STEERING COLUMN
4 - KNEE BLOCKER COVER
19 - 8 COLUMNWJ
COLUMN (Continued)

(13) Remove the column coupler bolt (Fig. 13) and
slide the coupler off the column shaft.
(14) Remove the column mounting nuts (Fig. 13)
and lower column off mounting studs. Remove the
column from the vehicle.
(15) Remove the ignition switch, cylinder and
SKIM, (Refer to 19 - STEERING/COLUMN/LOCK
CYLINDER HOUSING - REMOVAL). (Fig. 14).INSTALLATION
WARNING: BEFORE SERVICING THE STEERING COL-
UMN THE AIRBAG SYSTEM MUST BE DISARMED.
FAILURE TO DO SO MAY RESULT IN ACCIDENTAL
DEPLOYMENT OF THE AIRBAG AND POSSIBLE PER-
SONAL INJURY. (Refer to 8 - ELECTRICAL/RE-
STRAINTS/DRIVER AIRBAG - INSTALLATION).
(1) Install the ignition switch, cylinder and SKIM-
,(Refer to 19 - STEERING/COLUMN/IGNITION
SWITCH - INSTALLATION).
(2) Install the column into the vehicle and lift the
column up onto the mounting studs. Install the
mounting nuts and tighten to 12 N´m (105 in. lbs.).
(3) Slid the coupler onto the column shaft and
install the coupler bolt. Tighten the coupler bolt to 49
N´m (36 ft. lbs.).
(4) Turn the ignition key to the on position then
release and install the shifter interlock cable (Fig.
12) into ignition lock cylinder housing.
(5) Verify ignition switch and shifter interlock
operation.,(Refer to 21 - TRANSMISSION/TRANS-
AXLE/AUTOMATIC - 42RE/GEAR SHIFT CABLE -
ADJUSTMENTS).
(6) Slide the multifuction switch and clock spring
onto the column as an assembly (Fig. 11).
(7) Install the multifuction switch mounting screw
(Fig. 10).
(8) Connect the multifuction switch (Fig. 9) and
ignition switch harness.
(9) Install the upper fixed shroud and mounting
screws (Fig. 8).
(10) Install the lower steering column shroud to
the steering column. Install and tighten the mount-
ing screw.
(11) Install the upper column shroud. Align the
upper shroud to the lower shroud and snap the two
shroud halves together.
(12) Install the knee blocker cover (Fig. 5),(Refer
to 23 - BODY/INSTRUMENT PANEL - INSTALLA-
TION).
(13) Install the cluster bezel by inserting it into
the instrument panel (Fig. 4).
(14) Align the steering wheel with the column
index spline and install the wheel on the column
shaft. Pull the clockspring wire harness through the
steering wheel armature spokes.
(15) Install and tighten the steering wheel mount-
ing nut to 61 N´m (45 ft. lbs.).
(16) Connect the steering wheel wire harness con-
nector to the clock spring connector.
(17) Install the airbag,(Refer to 8 - ELECTRICAL/
RESTRAINTS/DRIVER AIRBAG - INSTALLATION).
(18) Connect the negative (ground) cable to the
battery.
Fig. 13 Column Coupler Bolt And Mounting Nuts
1 - COLUMN MOUNTING NUTS
2 - COUPLER BOLT
Fig. 14 Ignition Switch And SKIM
1 - SKIM
2 - IGNITION SWITCH
WJCOLUMN 19 - 11
COLUMN (Continued)

KEY-IN IGNITION SWITCH
DESCRIPTION
The key-in ignition switch is concealed within and
integral to the ignition switch, which is mounted on
the steering column. The key-in ignition switch is
actuated by the ignition lock cylinder mechanism,
and is hard wired between a body ground and the
Body Control Module (BCM) through the instrument
panel wire harness.
The key-in ignition switch cannot be adjusted or
repaired and, if faulty or damaged, the entire igni-
tion switch unit must be replaced,(Refer to 19 -
STEERING/COLUMN/LOCK CYLINDER HOUSING
- REMOVAL). For complete circuit diagrams, refer to
Body Control Modulein the Contents of Wiring
Diagrams.
OPERATION
The key-in ignition switch closes a path to ground
for the BCM when the ignition key is inserted in the
ignition lock cylinder, and opens the ground path
when the key is removed from the ignition lock cyl-
inder. The BCM monitors the key-in ignition switch
status through an internal pull-up, then sends the
proper switch status messages to other electronic
modules over the Programmable Communications
Interface (PCI) data bus network. The key-in ignition
switch status is also used by the BCM as an input
for chime warning system operation.
DIAGNOSIS AND TESTING
KEY-IN IGNITION SWITCH
For complete circuit diagrams, refer toBody Con-
trol Modulein the Contents of Wiring Diagrams.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO GROUP 8M - PASSIVE
RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING WHEEL, STEERING COLUMN, OR
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.(1) Disconnect and isolate the battery negative
cable. Disconnect the instrument panel wire harness
connector from the key-in ignition switch connector
receptacle on the ignition switch. Check for continu-
ity between the key-in ignition switch sense and
ground terminals of the key-in ignition switch con-
nector receptacle. There should be continuity with
the key inserted in the ignition lock cylinder, and no
continuity with the key removed from the ignition
lock cylinder. If OK, go to Step 2. If not OK, replace
the faulty ignition switch unit.
(2) Check for continuity between the ground cir-
cuit cavity of the instrument panel wire harness con-
nector for the key-in ignition switch and a good
ground. There should be continuity. If OK, go to Step
3. If not OK, repair the open ground circuit to ground
as required.
(3) Disconnect the gray 26-way instrument panel
wire harness connector from the Body Control Mod-
ule (BCM) connector receptacle. Check for continuity
between the key-in ignition switch sense circuit cav-
ity of the instrument panel wire harness connector
for the key-in ignition switch and a good ground.
There should be no continuity. If OK, go to Step 4. If
not OK, repair the shorted key-in ignition switch
sense circuit as required.
(4) Check for continuity between the key-in igni-
tion switch sense circuit cavities of the instrument
panel wire harness connector for the key-in ignition
switch and the gray 26-way instrument panel wire
harness connector for the BCM. There should be con-
tinuity. If OK, use a DRB scan tool and the proper
Diagnostic Procedures manual to test the BCM. If
not OK, repair the open key-in ignition switch sense
circuit as required.
LOCK CYLINDER
REMOVAL
The ignition key must be in the key cylinder for
cylinder removal. The key cylinder must be removed
first before removing ignition switch.
(1) Disconnect negative battery cable at battery.
(2) If equipped with an automatic transmission,
place shifter in PARK position.
(3) Rotate key to ON position.
19 - 14 COLUMNWJ

(4) A release tang is located on bottom of key cyl-
inder (Fig. 18).(5) Position a small screwdriver or pin punch into
tang access hole on bottom of steering column lower
cover (Fig. 19).
(6) Push the pin punch up while pulling key cylin-
der from steering column.
INSTALLATION
The ignition key must be in the key cylinder for
cylinder removal. The key cylinder must be removed
first before removing ignition switch.
(1) If equipped with an automatic transmission,
place shifter in PARK position.
(2) Position key cylinder into steering column as it
would normally be in the ON position.
(3) Press key cylinder into column until it snaps
into position.
(4) Check mechanical operation of switch.Auto-
matic Transmission:Be sure transmission lever is
locked in PARK position after key removal. If key is
difficult to rotate or is difficult to remove, the shift
lever-to-steering column cable may be out of adjust-
ment or defective. Refer to Transmission for proce-
dures.Manual Transmission:Be sure key cannot
be removed until release lever is operated. If key can
be removed, release lever mechanism may be defec-
tive. Release lever mechanism is not serviced sepa-
rately. If repair is necessary, the steering column
must be replaced,(Refer to 19 - STEERING/COL-
UMN - REMOVAL).
(5) Connect negative cable to battery.
(6) Check electrical operation of switch.
STEERING WHEEL
REMOVAL
For steering wheel removal procedure,(Refer to 8 -
ELECTRICAL/RESTRAINTS/CLOCKSPRING -
REMOVAL).
INSTALLATION
For steering wheel installation procedure,(Refer to
8 - ELECTRICAL/RESTRAINTS/CLOCKSPRING -
INSTALLATION).
Fig. 18 Key Cylinder Release Tang
1 - KEY CYLINDER
2 - RELEASE TANG
Fig. 19 Key Cylinder and Cover Removal
1 - LOWER COVER
2 - ACCESS HOLE
3 - PIN PUNCH
4 - COVER SCREWS (3)
WJCOLUMN 19 - 15
LOCK CYLINDER (Continued)

SPECIAL TOOLS
POWER STEERING PUMP
FLUID COOLER
DESCRIPTION
4.7L models of this vehicle are equipped with a
cooler for the power steering system fluid. The power
steering fluid cooler is located at the front of the
vehicle. It is mounted to the radiator support just
forward of the air-conditioning condenser and just
rearward of the front fascia (Fig. 6). The cooler is
positioned so it is in the air flow through the front
fascia of the vehicle.
REMOVAL
(1) Disconnect negative battery cable at battery.
(2) Drain the power steering fluid out of the reser-
voir.
(3) Remove the front fascia grille assembly,(Refer
to 13 - FRAMES & BUMPERS/BUMPERS/FRONT
FASCIA - REMOVAL).
(4) Remove the grille opening reinforcement panel
(5) Place a drain pan under the cooler.
(6) Disconnect the lower hose at cooler (Fig. 6).
(7) Disconnect the upper hose at cooler (Fig. 6).
(8) Remove the three cooler mounting bolts (Fig.
6).
(9) Remove the cooler from the vehicle.
Analyzer Set, Power Steering Flow/Pressure 6815
Adapters, Power Steering Flow/Pressure Tester
6893
4.7L HYDRAULIC POWER STEERING TEST
ADAPTER KIT - 8630
Puller C-4333
Installer, Power Steering Pulley C-4063B
Fig. 6 POWER STEERING FLUID COOLER
1 - POWER STEERING COOLER
2 - POWER STEERING COOLER LINES CLIP
19 - 36 PUMPWJ
PUMP (Continued)