2003 JEEP GRAND CHEROKEE frame

Programmable Communications Interface (PCI) data
bus network.
For diagnosis of the HSM, MHSM or the PCI data
bus, a DRBIIItscan tool and the proper Diagnostic
Procedures manual are recommended. The HSM or
MHSM cannot be repaired and, if faulty or damaged,
it must be replaced.
OPERATION
The MSM receives hard wired inputs from the
power seat switch and the potentiometers on each of
the driver side power seat motors. The MSM receives
messages over the PCI data bus from the Driver
Door Module (DDM) (memory switch status), the
Powertrain Control Module (PCM) (vehicle speed sta-
tus), and the Body Control Module (seat belt switch
status).The MSM will prevent the seat memory recall
function from being initiated if the driver side seat
belt is buckled, if the transmission gear selector lever
is not in the Park or Neutral positions, or if the vehi-
cle is moving.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - HEATED SEAT
MODULE
Visually inspect the related wiring harness connec-
tors. Look for broken, bent, pushed out, or corroded
terminals. If any of the above conditions are present,
repair as necessary. If not, use a DRBIIItscan tool
and the proper Diagnostic Procedures Manual to test
the HSM or MHSM. For complete circuit diagrams,
refer toPower Seat Premium I/IIIin Wiring Dia-
grams.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the driver side front bucket seat from
the power seat track unit. Refer toBucket Seat
Track Adjusterin Body for the procedure.
(3) Lift the heated seat module off of the power
seat track and disconnect the power seat wire har-
ness connectors (Fig. 10).
(4) Remove the module from the bracket.
Fig. 9 Heated Seat Module Remove/Install
1 - NUT (4)
2 - SEAT CUSHION FRAME
3 - POWER SEAT TRACK
4 - STUD (4)
5 - MODULE
6 - BRACKET
Fig. 10 Heated Seat Module Remove/Install
1 - NUT (4)
2 - SEAT CUSHION FRAME
3 - POWER SEAT TRACK
4 - STUD (4)
5 - MODULE
6 - BRACKET
WJELECTRONIC CONTROL MODULES 8E - 11
MEMORY HEATED SEAT/MIRROR MODULE (Continued)

SPECIAL TOOLS
BATTERY
DESCRIPTION
A large capacity, low-maintenance storage battery
(Fig. 4) is standard factory-installed equipment on
this model. Male post type terminals made of a soft
lead material protrude from the top of the molded
plastic battery case to provide the means for connect-
ing the battery to the vehicle electrical system. The
battery positive terminal post is visibly larger in
diameter than the negative terminal post, for easy
identification. The lettersPOSandNEGare also
molded into the top of the battery case adjacent to
their respective positive and negative terminal posts
for additional identification confirmation. Refer to
Battery Cablesin the index of this service manual
for the location of more information on the battery
cables that connect the battery to the vehicle electri-
cal system.
This battery is designed to provide a safe, efficient
and reliable means of storing electrical energy in a
chemical form. This means of energy storage allows
the battery to produce the electrical energy required
to operate the engine starting system, as well as to
operate many of the other vehicle accessory systems
for limited durations while the engine and/or the
charging system are not operating. The battery is
made up of six individual cells that are connected in
series. Each cell contains positively charged plate
groups that are connected with lead straps to thepositive terminal post, and negatively charged plate
groups that are connected with lead straps to the
negative terminal post. Each plate consists of a stiff
mesh framework or grid coated with lead dioxide
(positive plate) or sponge lead (negative plate). Insu-
lators or plate separators made of a non-conductive
material are inserted between the positive and nega-
tive plates to prevent them from contacting or short-
ing against one another. These dissimilar metal
plates are submerged in a sulfuric acid and water
solution called an electrolyte.
Some factory-installed batteries have a built-in test
indicator (hydrometer). The color visible in the sight
glass of the indicator will reveal the battery condi-
tion. For more information on the use of the built-in
test indicator, refer toStandard Procedures The
factory-installed low-maintenance battery has
removable battery cell caps.Distilled water can
be added to this battery. The battery is not sealed
and has vent holes in the cell caps. The chemical
composition of the metal coated plates within the
low-maintenance battery reduces battery gassing and
water loss, at normal charge and discharge rates.
Therefore, the battery should not require additional
water in normal service. If the electrolyte level in
this battery does become low, distilled water must be
added. However, rapid loss of electrolyte can be
caused by an overcharging condition. Be certain to
MICRO 420 BATTERY AND CHARGING SYSTEM
TESTER
Fig. 4 Low-Maintenance Battery - Typical
1 - POSITIVE POST
2 - VENT
3 - CELL CAP
4 - TEST INDICATOR
5 - CELL CAP
6 - VENT
7 - NEGATIVE POST
8 - GREEN BALL
9 - ELECTROLYTE LEVEL
10 - PLATE GROUPS
11 - LOW-MAINTENANCE BATTERY
WJBATTERY SYSTEM 8F - 7
BATTERY SYSTEM (Continued)

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)

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)

HEATED SEAT SENSOR
DESCRIPTION
The heated seat temperature sensor is a Negative
Temperature Coefficient (NTC) thermistor. One tem-
perature sensor is used for each seat. This tempera-
ture sensor is located in the seat cushion heating
element on all models.
The heated seat temperature sensor cannot be
repaired or adjusted and must be replaced if defec-
tive. The heated seat cushion element must be
replaced if the temperature sensor is defective. Refer
to the procedure in this section of the service man-
ual.
DIAGNOSIS AND TESTING - HEATED SEAT
SENSOR
For complete circuit diagrams, refer toWiring
Diagrams.
(1) Disconnect the Heated Seat Module (HSM) or
Memory Heated Seat Module (MHSM) C1 connector.
Check for continuity between the SEAT SENSOR 5V
SUPPLY circuit cavity and the seat cushion frame.
There should beNOcontinuity. If OK, go to Step 2.
If not OK, repair the shorted seat sensor 5V supply
circuit as required.
(2) Check for continuity between the SEAT SEN-
SOR 5V SUPPLY circuit cavity of the 4-way power
seat wire harness connector and the C1 connector for
the HSM or MHSM. There should be continuity. If
OK, go to Step 3. If not OK, repair the open seat sen-
sor 5V supply circuit as required.
(3) Connect the module electrical connector. Turn
system ON, using a voltmeter, backprobe the HSM or
MHSM C1 connector on the SEAT TEMPERATURE
SENSOR INPUT circuit cavity. Voltage should be
present (2-4 volts). If OK, proceed with testing the
other components in the heated seat system. If not
OK, refer to Heated Seat Module Diagnosis and Test-
ing in the electronic control modules section of this
manual.
REMOVAL
(1) For heated seat sensor replacement procedure
(Refer to 8 - ELECTRICAL/HEATED SEATS/
HEATED SEAT ELEMENT - REMOVAL).
PASSENGER HEATED SEAT
SWITCH
DESCRIPTION
The heated seat switches are mounted in the
instrument panel center lower bezel (Fig. 7), which is
located near the bottom of the instrument panel cen-
ter stack. The two three-position rocker-type
switches, one switch for each front seat, provide a
resistor multiplexed signal to the Body Control Mod-
ule (BCM) through separate hard wired circuits.
Each switch has an Off, Low, and High position so
that both the driver and the front seat passenger can
select a preferred seat heating mode. Each switch
has two Light-Emitting Diodes (LED), one each for
the Low position and the High position, which light
to indicate that the heater for the seat that the
switch controls is turned on. Each switch is also back
lit by a replaceable incandescent bulb.
The heated seat switches and their LEDs cannot
be repaired. If either switch or LED is faulty or dam-
aged, the entire switch unit must be replaced. The
incandescent switch illumination bulb and bulb
holder units are available for service replacement.
Fig. 7 HEATED SEAT SWITCHES
1 - HEATED SEAT SWITCHES
WJHEATED SEAT SYSTEM 8G - 15

REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) On models with the ten-way power seat system
only, using a push pin remover or another suitable
wide flat-bladed tool, gently pry the power seat and
power recliner switch knobs off of the switch stems
(Fig. 5).
(3) Remove the three screws that secure the out-
board seat cushion side shield to the seat cushion
frame.
(4) Pull the outboard seat cushion side shield away
from the seat cushion frame far enough to access the
power seat switch wire harness connector.
(5) Disconnect the power seat wire harness connec-
tor from the power seat switch connector receptacle.
(6) Remove the two screws that secure the power
seat switch to the inside of the outboard seat cushion
side shield (Fig. 6) or (Fig. 7).
(7) Remove the power seat switch from the out-
board seat cushion side shield.
INSTALLATION
(1) Position the power seat switch onto the out-
board seat cushion side shield.
(2) Install and tighten the two screws that secure
the power seat switch to the inside of the outboard
seat cushion side shield. Tighten the screws to 1.5
N´m (14 in. lbs.).
(3) Reconnect the power seat wire harness connec-
tor to the power seat switch connector receptacle.(4) Position the outboard seat cushion side shield
onto the seat cushion frame
(5) Install and tighten the three screws that secure
the outboard seat cushion side shield to the seat
cushion frame. Tighten the screws to 1.5 N´m (14 in.
lbs.).
(6) On models with the ten-way power seat system
only, position the power seat and power recliner
switch knobs onto the switch stems and push on
them firmly and evenly until they snap into place.
(7) Reconnect the battery negative cable.
Fig. 5 Removing Switch Control Knobs - Typical
Fig. 6 Six-Way Power Seat Switches Remove/Install
1 - SEAT SIDE SHIELD
2 - POWER SEAT SWITCH
3 - SCREWS
Fig. 7 Ten-Way Power Seat Switches Remove/Install
1 - POWER SEAT SWITCH
2 - SCREWS (2)
3 - POWER LUMBAR SWITCH
4 - SEAT CUSHION SIDE SHIELD
5 - WIRE HARNESS CONNECTOR
WJPOWER SEAT SYSTEM 8N - 23
DRIVER SEAT SWITCH (Continued)

(2) Remove the three screws that secure the out-
board seat cushion side shield to the seat cushion
frame.
(3) Pull the outboard seat cushion side shield away
from the seat cushion frame far enough to access the
power lumbar switch wire harness connector.
(4) Disconnect the power seat wire harness connec-
tor from the power lumbar switch connector recepta-
cle (Fig. 10).
(5) Remove the two screws that secure the power
lumbar switch to the inside of the outboard seat
cushion side shield.
(6) Remove the power lumbar switch from the out-
board seat cushion side shield.
INSTALLATION
(1) Position the power lumbar switch onto the out-
board seat cushion side shield.
(2) Install and tighten the two screws that secure
the power lumbar switch to the inside of the out-
board seat cushion side shield. Tighten the screws to
1.5 N´m (14 in. lbs.).
(3) Reconnect the power seat wire harness connec-
tor to the power lumbar switch connector receptacle.
(4) Position the outboard seat cushion side shield
onto the seat cushion frame(5)
Install and tighten the three screws that secure
the outboard seat cushion side shield to the seat cush-
ion frame. Tighten the screws to 1.5 N´m (14 in. lbs.).
(6) Reconnect the battery negative cable.
LUMBAR MOTOR
DESCRIPTION
The ten-way power seat option includes an electri-
cally operated lumbar support mechanism. The only
visible evidence of this option is the separate power
lumbar switch control paddle that is located on the
outboard seat cushion side shield, just forward of the
other power seat switch control knobs. The power
lumbar adjuster and motor are concealed beneath the
seat back trim cover and padding, where they are
secured to a molded plastic back panel and to the
seat back frame (Fig. 11).
The power lumbar adjuster cannot be repaired, and
is serviced only as a unit with the seat back frame. If
the power lumbar adjuster or the seat back frame
are damaged or faulty, the entire seat back frame
unit must be replaced.
Fig. 10 Power Lumbar Switch Remove/Install
1 - OUTBOARD SEAT CUSHION SIDE SHIELD
2 - POWER LUMBAR SWITCH
3 - WIRE HARNESS CONNECTOR
4 - SCREWS (2)
Fig. 11 Power Lumbar Adjuster
1 - SEAT BACK FRAME
2 - SEAT BACK PANEL
3 - LUMBAR MOTOR PIGTAIL TO SEAT WIRE HARNESS
4 - TIE WRAP
5 - SCREW (3)
6 - POWER LUMBAR ADJUSTER
7 - SEAT BACK TRIM COVER AND PADDING
WJPOWER SEAT SYSTEM 8N - 25
LUMBAR CONTROL SWITCH (Continued)

OPERATION
The power lumbar adjuster mechanism includes a
reversible electric motor that is secured to the
inboard side of the seat back panel and is connected
to a worm-drive gearbox. The motor and gearbox
operate the lumbar adjuster mechanism in the center
of the seat back by extending and retracting a cable
that actuates a lever. The action of this lever com-
presses or relaxes a grid of flexible slats. The more
this grid is compressed, the more the slats bow out-
ward against the center of the seat back padding,
providing additional lumbar support.
DIAGNOSIS AND TESTING - POWER LUMBAR
ADJUSTER
Actuate the power lumbar switch to move the
power lumbar adjuster in each direction. The power
lumbar adjuster should move in both directions. It
should be noted that the power lumber adjuster nor-
mally operates very quietly and exhibits little visible
movement. If the power lumbar adjuster fails to oper-
ate in only one direction, move the adjuster a short
distance in the opposite direction and test again to be
certain that the adjuster is not at its travel limit. If
the power lumbar adjuster still fails to operate in
only one direction, refer toDiagnosis and Testing
Power Lumbar Switchin this group. If the power
lumbar adjuster fails to operate in either direction,
perform the following tests. For complete circuit dia-
grams, refer toWiring Diagrams.
(1) Check the power seat circuit breaker in the
junction block. If OK, go to Step 2. If not OK, replace
the faulty power seat circuit breaker.
(2) Check for battery voltage at the power seat cir-
cuit breaker in the junction block. If OK, go to Step
3. If not OK, repair the open fused B(+) circuit to the
fuse in the Power Distribution Center as required.
(3) Remove the outboard seat cushion side shield
from the seat. Disconnect the seat wire harness con-
nector from the power lumbar switch connector
receptacle. Check for battery voltage at the fused
B(+) circuit cavity of the power seat wire harness
connector for the power lumbar switch. If OK, go to
Step 4. If not OK, repair the open fused B(+) circuit
to the power seat circuit breaker in the junction
block as required.
(4) Check for continuity between the ground cir-
cuit cavity of the power seat wire harness connector
for the power lumbar switch and a good ground.
There should be continuity. If OK, go to Step 5. If not
OK, repair the open ground circuit to ground as
required.
(5) Test the power lumbar switch. Refer toDiag-
nosis and Testing Power Lumbar Switchin this
group. If the switch tests OK, test the circuits of the
power seat wire harness between the power lumbaradjuster motor and the power lumbar switch for
shorts or opens. If the circuits check OK, replace the
faulty seat back frame assembly. If the circuits are
not OK, repair the power seat wire harness as
required.
MEMORY SET SWITCH
DESCRIPTION
Vehicles equipped with the memory system have a
memory switch mounted to the driver side front door
trim panel (Fig. 12). This switch is used to set and
recall all of the memory system settings for up to two
drivers. The memory switch is a resistor multiplexed
unit that is hard wired to the Driver Door Module
(DDM), which is also located on the driver side front
door trim panel. The DDM sends out the memory
system set and recall requests to the other electronic
modules over the Programmable Communications
Interface (PCI) data bus.
The memory switch cannot be adjusted or repaired
and, if faulty or damaged, it must be replaced. For
complete circuit diagrams, refer toWiring Diagrams
.
OPERATION
The memory switch has three momentary switch
buttons labeled Set, 1 and 2. The Driver 1 and Driver
2 buttons are back-lit with Light-Emitting Diodes
Fig. 12 WJ/WG MEMORY SELECT/SET SWITCH
1 - DRIVER TRIM PANEL
2 - MEMORY SWITCH
8N - 26 POWER SEAT SYSTEMWJ
LUMBAR MOTOR (Continued)