2002 JEEP GRAND CHEROKEE ECU

INSTALLATION
(1) Clean and inspect the battery tray and support
unit. Refer to the procedures in this section of the
service manual.
(2) Install the battery temperature sensor onto the
battery tray. Refer toBattery Temperature Sensor
in the Charging section of this service manual for
battery temperature sensor installation procedure.
(3) Position the battery tray and support unit into
the right front corner of the engine compartment. Be
certain that no hoses or wire harnesses are trapped
or pinched by the installation of the tray.
(4) Install and tighten the one nut that secures the
rear of the battery tray and support unit to the stud
on the right fender front wheelhouse inner panel.
Tighten the nut to 7.3 N´m (65 in. lbs.).(5) Install and tighten the one screw that secures
the outboard side of the battery tray and support
unit to the right fender side cowl reinforcement.
Tighten the screw to 8.1 N´m (72 in. lbs.).
(6) Install and tighten the one screw that secures
the front of the battery tray and support unit to the
bracket on the right side of the radiator support.
Tighten the screw to 8.1 N´m (72 in. lbs.).
(7) Install the Power Distribution Center (PDC)
onto the stanchions on the outboard side of the bat-
tery tray and support unit. Refer toPower Distri-
bution Centerin the Power Distribution section of
this service manual for PDC installation procedure.
(8) Install the battery onto the battery tray (Refer
to 8 - ELECTRICAL/BATTERY SYSTEM/BATTERY -
INSTALLATION).
WJBATTERY SYSTEM 8F - 23
BATTERY TRAY (Continued)

STARTING
TABLE OF CONTENTS
page page
STARTING
DESCRIPTION.........................29
OPERATION...........................30
DIAGNOSIS AND TESTING - STARTING
SYSTEM............................30
SPECIFICATIONS
TORQUE - STARTER...................35
STARTER MOTOR - GAS POWERED......35
STARTER MOTOR
DESCRIPTION.........................35
OPERATION...........................36DIAGNOSIS AND TESTING - STARTER
MOTOR .............................36
REMOVAL.............................37
INSTALLATION.........................38
STARTER MOTOR RELAY
DESCRIPTION.........................38
OPERATION...........................38
DIAGNOSIS AND TESTING - STARTER RELAY . 38
REMOVAL.............................39
INSTALLATION.........................40
STARTING
DESCRIPTION
An electrically operated engine starting system is
standard factory-installed equipment on this model.
The starting system is designed to provide the vehi-
cle operator with a convenient, efficient and reliable
means of cranking and starting the internal combus-
tion engine used to power the vehicle and all of its
accessory systems from within the safe and secure
confines of the passenger compartment. See the own-
er's manual in the vehicle glove box for more infor-
mation and instructions on the recommended use
and operation of the factory-installed starting sys-
tem.
The starting system consists of the following com-
ponents:
²Battery
²Starter relay
²Starter motor (including an integral starter sole-
noid)
²Ignition switch
²Park/neutral position switch
²Wire harnesses and connections (including the
battery cables).
This group provides complete service information
for the starter motor and the starter relay. Complete
service information for the other starting system
components can be located as follows:
²Refer toBatteryin the proper section of Group
8A - Battery for complete service information for the
battery.
²Refer toIgnition Switch and Key Lock Cyl-
inderin the proper section of Group 8D - Ignition
System for complete service information for the igni-
tion switch.²Refer toPark/Neutral Position Switchin the
proper section of Group 21 - Transmission for com-
plete service information for the park/neutral posi-
tion switch.
²Refer to the proper section ofGroup 8W - Wir-
ing Diagramsfor complete service information and
circuit diagrams for the starting system wiring com-
ponents.
Group 8A covers the Battery, Group 8B covers the
Starting Systems, and Group 8C covers the Charging
System. We have separated these systems to make it
easier to locate the information you are seeking
within this Service Manual. However, when attempt-
ing to diagnose any of these systems, it is important
that you keep their interdependency in mind.
The battery, starting, and charging systems in the
vehicle operate with one another, and must be tested
as a complete system. In order for the vehicle to start
and charge properly, all of the components that are
used in these systems must perform within specifica-
tions.
The diagnostic procedures used in each of these
groups include the most basic conventional diagnostic
methods, to the more sophisticated On-Board Diag-
nostics (OBD) built into the Powertrain Control Mod-
ule (PCM). Use of an induction-type milliampere
ammeter, volt/ohmmeter, battery charger, carbon pile
rheostat (load tester), and 12-volt test lamp may be
required.
All OBD-sensed systems are monitored by the
PCM. Each monitored circuit is assigned a Diagnos-
tic Trouble Code (DTC). The PCM will store a DTC in
electronic memory for any failure it detects. Refer to
On-Board Diagnostic Test For Charging System
in the Diagnosis and Testing section of Group 8C -
Charging System for more information.
WJSTARTING 8F - 29

OPERATION
These starter motors are equipped with a plane-
tary gear reduction (intermediate transmission) sys-
tem. The planetary gear reduction system consists of
a gear that is integral to the output end of the elec-
tric motor armature shaft that is in continual
engagement with a larger gear that is splined to the
input end of the starter pinion gear shaft. This fea-
ture makes it possible to reduce the dimensions of
the starter. At the same time, it allows higher arma-
ture rotational speed and delivers increased torque
through the starter pinion gear to the starter ring
gear.
The starter motors for both engines are activated
by an integral heavy duty starter solenoid switch
mounted to the overrunning clutch housing. This
electromechanical switch connects and disconnects
the feed of battery voltage to the starter motor and
actuates a shift fork that engages and disengages the
starter pinion gear with the starter ring gear.
Both starter motors use an overrunning clutch and
starter pinion gear unit to engage and drive a starter
ring gear that is integral to the torque converter
drive plate mounted on the rear crankshaft flange.
DIAGNOSIS AND TESTING - STARTER MOTOR
Correct starter motor operation can be confirmed
by performing the following free running bench test.
This test can only be performed with the starter
motor removed from the vehicle. Refer toStarting
Systemin the Specifications section of this group for
the starter motor specifications.
(1) Remove the starter motor from the vehicle.
Refer toStarter Motorin the Removal and Instal-
lation section of this group for the procedures.
(2) Mount the starter motor securely in a soft-
jawed bench vise. The vise jaws should be clamped
on the mounting flange of the starter motor. Never
clamp on the starter motor by the field frame.
(3) Connect a suitable volt-ampere tester and a
12-volt battery to the starter motor in series, and set
the ammeter to the 100 ampere scale. See the
instructions provided by the manufacturer of the
volt-ampere tester being used.
(4) Install a jumper wire from the solenoid termi-
nal to the solenoid battery terminal. The starter
motor should operate. If the starter motor fails to
operate, replace the faulty starter motor assembly.
(5) Adjust the carbon pile load of the tester to
obtain the free running test voltage. Refer toStart-
ing Systemin the Specifications section of this
group for the starter motor free running test voltage
specifications.
(6) Note the reading on the ammeter and compare
this reading to the free running test maximum
amperage draw. Refer toStarting Systemin theSpecifications section of this group for the starter
motor free running test maximum amperage draw
specifications.
(7) If the ammeter reading exceeds the maximum
amperage draw specification, replace the faulty
starter motor assembly.
STARTER SOLENOID
This test can only be performed with the starter
motor removed from the vehicle.
(1) Remove the starter motor from the vehicle.
Refer toStarter Motorin the Removal and Instal-
lation section of this group for the procedures.
(2) Disconnect the wire from the solenoid field coil
terminal.
(3) Check for continuity between the solenoid ter-
minal and the solenoid field coil terminal with a con-
tinuity tester (Fig. 7). There should be continuity. If
OK, go to Step 4. If not OK, replace the faulty starter
motor assembly.
(4) Check for continuity between the solenoid ter-
minal and the solenoid case (Fig. 8). There should be
continuity. If not OK, replace the faulty starter motor
assembly.
Fig. 7 Continuity Test Between Solenoid Terminal
and Field Coil Terminal - Typical
1 - SOLENOID
2 - SOLENOID TERMINAL
3 - OHMMETER
4 - FIELD COIL TERMINAL
Fig. 8 Continuity Test Between Solenoid Terminal
1 - SOLENOID
2 - SOLENOID TERMINAL
3 - OHMMETER
8F - 36 STARTINGWJ
STARTER MOTOR (Continued)

REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Raise and support the vehicle.
(3) Remove the lower (forward facing) mounting
screw securing the starter motor to the automatic
transmission torque converter housing (Fig. 9) or
(Fig. 10) .
(4) While supporting the starter motor with one
hand, use the other hand to remove the upper (rear
facing) mounting screw securing the starter motor to
the automatic transmission torque converter housing.
(5) Lower the starter motor from the front of the
automatic transmission torque converter housing far
enough to access and remove the nut that secures
the battery cable eyelet to the solenoid battery termi-
nal (Fig. 11) or (Fig. 12) . Always support the starter
motor during this process, do not let the starter
motor hang from the wire harness.
(6) Remove the battery cable eyelet from the sole-
noid battery terminal. Always support the starter
motor during this process, do not let the starter
motor hang from the wire harness.
(7) Disconnect the solenoid terminal wire harness
connector from the connector receptacle on the
starter solenoid. Always support the starter motor
during this process, do not let the starter motor hang
from the wire harness.
Fig. 9 Starter Motor Remove/Install - 4.0L Engine
1 - SCREW
2 - STARTER MOTOR
3 - SCREW
Fig. 10 Starter Motor Remove/Install - 4.7L Engine
1 - SCREW
2 - STARTER MOTOR
3 - SCREW
Fig. 11 Starter Wire Harness Remove/Install - 4.0L
Engine
1 - BATTERY, STARTER AND GENERATOR WIRE HARNESS
2 - GROUND EYELET
3 - SCREW
4 - NUT
5 - SOLENOID TERMINAL CONNECTOR
6 - SOLENOID BATTERY TERMINAL EYELET
7 - RETAINERS
WJSTARTING 8F - 37
STARTER MOTOR (Continued)

(8) Remove the starter motor from the engine com-
partment.
INSTALLATION
(1) Position the starter motor in the engine com-
partment.
(2) Reconnect the solenoid terminal wire harness
connector to the connector receptacle on the starter
solenoid. Always support the starter motor during
this process, do not let the starter motor hang from
the wire harness.
(3) Install the battery cable eyelet onto the sole-
noid battery terminal. Always support the starter
motor during this process, do not let the starter
motor hang from the wire harness.
(4) Install and tighten the nut that secures the
battery cable eyelet to the solenoid battery terminal.
Tighten the nut to 11.3 N´m (100 in. lbs.). Always
support the starter motor during this process, do not
let the starter motor hang from the wire harness.
(5) Position the starter motor to the front of the
automatic transmission torque converter housing and
loosely install both the upper and lower mounting
screws.
(6) Tighten the lower (forward facing) starter
motor mounting screw. On 4.0L engines, tighten the
screw to 41 N´m (30 ft. lbs.). On 4.7L engines, tighten
the screw to 54 N´m (40 ft. lbs.).(7) Tighten the upper (rearward facing) starter
mounting screw. Tighten the screw to 54 N´m (40 ft.
lbs.).
(8) Lower the vehicle.
(9) Reconnect the battery negative cable.
STARTER MOTOR RELAY
DESCRIPTION
The starter relay is an electromechanical device
that switches battery current to the pull-in coil of the
starter solenoid when the ignition switch is turned to
the Start position. The starter relay is located in the
Power Distribution Center (PDC), in the engine com-
partment. See the fuse and relay layout label affixed
to the inside surface of the PDC cover for starter
relay identification and location.
The starter relay is a International Standards
Organization (ISO) micro-relay. Relays conforming to
the ISO specifications have common physical dimen-
sions, current capacities, terminal patterns, and ter-
minal functions. The ISO micro-relay terminal
functions are the same as a conventional ISO relay.
However, the ISO micro-relay terminal pattern (or
footprint) is different, the current capacity is lower,
and the physical dimensions are smaller than those
of the conventional ISO relay.
The starter relay cannot be repaired or adjusted
and, if faulty or damaged, it must be replaced.
OPERATION
The ISO relay consists of an electromagnetic coil, a
resistor or diode, and three (two fixed and one mov-
able) electrical contacts. The movable (common feed)
relay contact is held against one of the fixed contacts
(normally closed) by spring pressure. When the elec-
tromagnetic coil is energized, it draws the movable
contact away from the normally closed fixed contact,
and holds it against the other (normally open) fixed
contact.
When the electromagnetic coil is de-energized,
spring pressure returns the movable contact to the
normally closed position. The resistor or diode is con-
nected in parallel with the electromagnetic coil in the
relay, and helps to dissipate voltage spikes that are
produced when the coil is de-energized.
DIAGNOSIS AND TESTING - STARTER RELAY
The starter relay (Fig. 13) is located in the Power
Distribution Center (PDC), in the engine compart-
ment. Refer to the fuse and relay layout label affixed
to the underside of the PDC cover for starter relay
identification and location. For complete circuit dia-
grams, refer toStarting Systemin the Contents of
Group 8W - Wiring Diagrams.
Fig. 12 Starter Wire Harness Remove/Install - 4.7L
Engine
1 - SOLENOID BATTERY TERMINAL EYELET
2 - NUT
3 - SOLENOID TERMINAL CONNECTOR
4 - BATTERY STARTER AND GENERATOR WIRE HARNESS
5 - RETAINERS
8F - 38 STARTINGWJ
STARTER MOTOR (Continued)

(1) Confirm that the ignition switch is in the On
position.
(2) Ensure that the rear glass heating grid feed
and ground terminals are connected to the glass.
Confirm that the ground wire has continuity to
ground.
(3) Check the fused B(+) fuse in the Power Distri-
bution Center (PDC). The fuse must be tight in its
receptacles and all electrical connections must be
secure.
When the above steps have been completed and the
rear glass heating grid is still inoperative, one or
more of the following is faulty:
²Rear window defogger switch
²Rear window defogger relay
²Body Control Module (BCM)
²Rear window grid lines (all grid lines would
have to be broken or one of the feed wires discon-
nected for the entire system to be inoperative).
When the above steps have been completed and the
heated mirror glass heating grid is still inoperative,
one or more of the following is faulty:
²Body Control Module (BCM)
²Programmable Communications Interface (PCI)
data bus
²Driver Door Module (DDM) or Passenger Door
Module (PDM)
²Outside rear view mirror heating grids.
If turning the rear window defogger system on pro-
duces a severe voltmeter deflection, check for a short
circuit between the rear window defogger relay out-
put and the rear glass heating grid.
REAR WINDOW DEFOGGER
GRID
DESCRIPTION
The electrically heated rear window glass is stan-
dard equipment on this model. The liftgate flip-up
glass has two electrically conductive vertical bus bars
and a series of horizontal grid lines made of a silver-
ceramic material, which is baked on and bonded to
the inside surface of the glass. These grid lines and
the bus bars comprise a parallel electrical circuit. A
spade type terminal near the top of each bus bar
accept the connectors from the two coiled liftgate
wire harness take outs.
The grid lines and bus bars are highly resistant to
abrasion. However, it is possible for an open circuit
to occur in an individual grid line, resulting in no
current flow through the line. The grid lines can be
damaged or scraped off with sharp instruments. Care
should be taken when cleaning the glass or removing
foreign materials, decals, or stickers from the glass.Normal glass cleaning solvents or hot water used
with rags or toweling is recommended.
A repair kit is available to repair the grid lines and
bus bars, or to reinstall the heated glass terminals.
(Refer to 8 - ELECTRICAL/HEATED GLASS/REAR
WINDOW DEFOGGER GRID - STANDARD PROCE-
DURE)
OPERATION
The rear glass heating grid is energized and de-en-
ergized by the rear window defogger relay. The Body
Control Module (BCM) monitors the rear window
defogger switch. When the BCM receives an input
from the switch, it energizes or de-energizes the rear
window defogger relay through a hard wired control
output. The rear defogger relay switches fused bat-
tery current to the rear window grid lines through
the bus bars. The grid lines heat the rear window
glass to clear the surface of ice, snow or fog. Protec-
tion for the rear glass heating grid circuit is provided
by a fuse in the Power Distribution Center (PDC).
DIAGNOSIS AND TESTING - REAR WINDOW
DEFOGGER GRID
For complete circuit diagrams, (Refer to Appropri-
ate Wiring Information). To detect breaks in the rear
glass heating grid lines, the following procedure is
required:
(1) Turn the ignition switch to the On position.
Turn the rear window defogger system on. The rear
window defogger switch LED indicator should light.
If OK, go to Step 2. If not OK, (Refer to 8 - ELEC-
TRICAL/HEATED GLASS/REAR WINDOW DEFOG-
GER RELAY - DIAGNOSIS AND TESTING).
(2) Using a 12-volt DC voltmeter, contact the rear
glass heating grid vertical bus bar on the right side
of the vehicle with the negative lead. With the posi-
tive lead, contact the rear glass heating grid vertical
bus bar on the left side of the vehicle. The voltmeter
should read battery voltage. If OK, go to Step 3. If
not OK, repair the open rear window defogger relay
output circuit to the rear window defogger relay as
required.
(3) With the positive voltmeter lead still contacting
the rear glass heating grid vertical bus bar on the
left side of the vehicle, move the negative lead of the
voltmeter to a good body ground point. The voltage
reading should not change. If OK, go to Step 4. If not
OK, repair the ground circuit to ground as required.
(4) Connect the negative lead of the voltmeter to
the right side bus bar and touch each grid line at
midpoint C with the positive lead (Fig. 2). A reading
of approximately six volts indicates a line is good. A
reading of zero volts indicates a break in the grid
line between midpoint C and the left side rear glass
heating grid bus bar. A reading of ten to fourteen
WJHEATED GLASS 8G - 3
HEATED GLASS (Continued)

(2) Remove the center lower bezel from the instru-
ment panel. Refer toInstrument Panel Center
Lower Bezelin the Body section of this manual for
the procedure.
(3) Remove the four screws that secure the heated
seat switch to the back of the instrument panel cen-
ter lower bezel (Fig. 4).
(4) Remove the heated seat switch from the back
of the instrument panel center lower bezel.
INSTALLATION
(1) Position the heated seat switch onto the back
of the instrument panel center lower bezel.
(2) Install and tighten the four screws that secure
the heated seat switch to the back of the instrument
panel center lower bezel. Tighten the screws to 1.5
N´m (13 in. lbs.).
(3) Install the center lower bezel onto the instru-
ment panel. Refer toInstrument Panel Center
Lower Bezelin the Body section of this manual for
the procedure.
(4) Reconnect the battery negative cable.
HEATED SEAT ELEMENT
DESCRIPTION
The heated seat system includes two seat heating ele-
ments in each front seat, one for the seat cushion (Fig.
5)and the other for the seat back. One type of heated
seat element is offered. All models use two resistor wire
heating elements for each seat that are connected in
series with the Heated Seat Module (HSM).
The seat heating elements are glued to the seat and
seat back cushions. The heated seat elements can be
replaced if faulty or damaged, service replacement seat
or seat back elements are available. Refer to the pro-
cedure in this section for detailed instructions.
OPERATION
The heated seat elements resist the flow of electri-
cal current. When battery current is passed through
the elements, the energy lost by the resistance of the
elements to the current flow is released in the form
of heat. The temperature sensor is a NTC thermistor.
When the temperature of the seat cushion cover
rises, the resistance of the sensor decreases. The
HSM or MHSM supplies a five-volt current to one
side of each sensor, and monitors the voltage drop
through the sensor on a return circuit. The MSM or
MHSM uses this temperature sensor input to moni-
tor the temperature of the seat, and regulates the
current flow to the seat heating elements accordingly.
Fig. 4 Heated Seat Switch Remove/Install
1 - HEATED SEAT SWITCHES
2 - SCREWS (4)
3 - CENTER LOWER BEZEL
4 - CIGAR LIGHTER
5 - ILLUMINATION LAMPS
6 - POWER OUTLET
Fig. 5 HEATING ELEMENT INSTALLED
1 - SEAT BACK WIRE HARNESS
2 - HEATED SEAT WIRE HARNESS CONNECTOR
3 - HEATED SEAT CUSHION ELEMENT
WJHEATED SEAT SYSTEM 8G - 13
DRIVER HEATED SEAT SWITCH (Continued)

DIAGNOSIS AND TESTING - HEATED SEAT
ELEMENT
RESISTOR WIRE ELEMENT
(1) Disconnect and isolate the battery negative
cable. The power seat wire harness connectors for the
seat cushion and seat back heating elements are
secured to a bracket located under the rear edge of
the seat cushion frame. Refer toWiringfor complete
circuit schematics and connector locations.
(2) Disconnect the Heated Seat Module (HSM) or
Memory Heated Seat Module (MHSM) C2 connector.
Check for continuity between the SEAT HEATER
B(+) DRIVER circuit cavity of the C2 connector and
the seat cushion frame. There should be NO continu-
ity. If OK, go to Step 3. If not OK, repair the shorted
seat heater B(+) driver circuit as required.
NOTE: WHEN CHECKING HEATED SEAT ELE-
MENTS FOR CONTINUITY, BE CERTAIN TO MOVE
THE HEATING ELEMENT BEING CHECKED. MOV-
ING THE ELEMENT, SUCH AS SITTING IN THE SEAT
WILL ELIMINATE THE POSSIBILITY OF AN INTER-
MITTENT OPEN IN THE ELEMENT WHICH WOULD
ONLY BE EVIDENT IF THE ELEMENT WAS MOVED
IN A CERTAIN DIRECTION. FAILURE TO CHECK
THE ELEMENT IN VARIOUS POSITIONS COULD
RESULT IN AN INCOMPLETE TEST.
(3) Check for continuity between the SEAT
HEATER B(+) DRIVER circuit cavity of the C2 con-
nector and the ground circuit cavity. There should be
continuity at all times (even upon moving or sitting
in the seat). If OK, proceed with testing the other
components in the heated seat system. If not OK,
replace the open heating element. Refer to the proce-
dure in this section of the manual.
REMOVAL
(1) Disconnect and isolate the negative battery
cable.
(2) Remove the appropriate seat cushion or seat
back trim cover. Refer to the Body section of the ser-
vice manual for the procedures.
(3) Disconnect the inoperative heated seat cushion
or seat back element electrical connectors.
(4) Gently peel-off defective heater element from
foam cushion.
INSTALLATION
(1) Peel off the adhesive backing on the back of the
replacement heating element and install on cushion
pad in the same location as the original (Fig. 6).
CAUTION: During the installation of the replace-
ment heating element, be very careful not to fold or
crease the element assembly. Folds or creases will
cause premature failure.
(2) Connect the new heating element electrical
connectors (Fig. 6).
(3) Connect the negative battery cable.
(4) Verify heated seat system operation.
(5) Install the appropriate seat cushion or seat
back trim cover. Make certain the seat wire harness
is correctly routed through the seat and seat back.
The excess wire between the cushion and back ele-
ments should be securely tucked between the rear of
the cushion foam and the rear carpet flap of the trim
cover.
Fig. 6 HEATING ELEMENT INSTALLED
1 - SEAT BACK WIRE HARNESS
2 - HEATED SEAT WIRE HARNESS CONNECTOR
3 - HEATED SEAT CUSHION ELEMENT
8G - 14 HEATED SEAT SYSTEMWJ
HEATED SEAT ELEMENT (Continued)