Electric control JEEP GRAND CHEROKEE 2003 WJ / 2.G Owner's Guide

STANDARD PROCEDURE - IGNITION-OFF
DRAW TEST
The term Ignition-Off Draw (IOD) identifies a nor-
mal condition where power is being drained from the
battery with the ignition switch in the Off position. A
normal vehicle electrical system will draw from five
to thirty-five milliamperes (0.005 to 0.035 ampere)
with the ignition switch in the Off position, and all
non-ignition controlled circuits in proper working
order. Up to thirty-five milliamperes are needed to
enable the memory functions for the Powertrain Con-
trol Module (PCM), digital clock, electronically tuned
radio, and other modules which may vary with the
vehicle equipment.
A vehicle that has not been operated for approxi-
mately twenty days, may discharge the battery to an
inadequate level. When a vehicle will not be used for
twenty days or more (stored), remove the IOD fuse
from the Power Distribution Center (PDC). This will
reduce battery discharging.Excessive IOD can be caused by:
²Electrical items left on.
²Faulty or improperly adjusted switches.
²Faulty or shorted electronic modules and compo-
nents.
²An internally shorted generator.
²Intermittent shorts in the wiring.
If the IOD is over thirty-five milliamperes, the
problem must be found and corrected before replac-
ing a battery. In most cases, the battery can be
charged and returned to service after the excessive
IOD condition has been corrected.
(1) Verify that all electrical accessories are off.
Turn off all lamps, remove the ignition key, and close
all doors. If the vehicle is equipped with an illumi-
nated entry system or an electronically tuned radio,
allow the electronic timer function of these systems
to automatically shut off (time out). This may take
up to three minutes. See the Electronic Module Igni-
tion-Off Draw Table for more information.
ELECTRONIC MODULE IGNITION-OFF DRAW (IOD) TABLE
ModuleTime Out?
(If Yes, Interval And Wake-Up Input)IODIOD After Time
Out
Radio No1to3
milliamperesN/A
Audio Power
AmplifierNoup to 1
milliampereN/A
Body Control Module
(BCM)No5.90
milliamperes
(max.)N/A
Powertrain Control
Module (PCM)No 0.95 milliampere N/A
Transmission Control
Module (TCM) 4.7L
w/45RFEYES (20 minutes, ignition on) 130 milliamperes 0.64 milliampere
ElectroMechanical
Instrument Cluster
(EMIC)No 0.44 milliampere N/A
Combination Flasher No 0.08 milliampere N/A
(2) Determine that the underhood lamp is operat-
ing properly, then disconnect the lamp wire harness
connector or remove the lamp bulb.
(3) Disconnect the battery negative cable.
(4) Set an electronic digital multi-meter to its
highest amperage scale. Connect the multi-meter
between the disconnected battery negative cable ter-
minal clamp and the battery negative terminal post.
Make sure that the doors remain closed so that the
illuminated entry system is not activated. The multi-
meter amperage reading may remain high for up tothree minutes, or may not give any reading at all
while set in the highest amperage scale, depending
upon the electrical equipment in the vehicle. The
multi-meter leads must be securely clamped to the
battery negative cable terminal clamp and the bat-
tery negative terminal post. If continuity between the
battery negative terminal post and the negative cable
terminal clamp is lost during any part of the IOD
test, the electronic timer function will be activated
and all of the tests will have to be repeated.
WJBATTERY SYSTEM 8F - 13
BATTERY (Continued)

²a faulty or improperly adjusted switch that
allows a lamp to stay on. Refer to Ignition-Off Draw
Test in 8, Battery for more information.
INSPECTION
The Powertrain Control Module (PCM) monitors
critical input and output circuits of the charging sys-
tem, making sure they are operational. A Diagnostic
Trouble Code (DTC) is assigned to each input and
output circuit monitored by the On-Board Diagnostic
(OBD) system. Some charging system circuits are
checked continuously, and some are checked only
under certain conditions.
Refer to Diagnostic Trouble Codes in; Powertrain
Control Module; Electronic Control Modules for more
DTC information. This will include a complete list of
DTC's including DTC's for the charging system.
To perform a complete test of the charging system,
refer to the appropriate Powertrain Diagnostic Proce-
dures service manual and the DRBtscan tool. Per-
form the following inspections before attaching the
scan tool.(1) Inspect the battery condition. Refer to 8, Bat-
tery for procedures.
(2) Inspect condition of battery cable terminals,
battery posts, connections at engine block, starter
solenoid and relay. They should be clean and tight.
Repair as required.
(3) Inspect all fuses in both the fuseblock and
Power Distribution Center (PDC) for tightness in
receptacles. They should be properly installed and
tight. Repair or replace as required.
(4) Inspect generator mounting bolts for tightness.
Replace or tighten bolts if required. Refer to the Gen-
erator Removal/Installation section of this group for
torque specifications.
(5) Inspect generator drive belt condition and ten-
sion. Tighten or replace belt as required. Refer to
Belt Tension Specifications in 7, Cooling System.
(6) Inspect automatic belt tensioner (if equipped).
Refer to 7, Cooling System for information.
(7) Inspect generator electrical connections at gen-
erator field, battery output, and ground terminal (if
equipped). Also check generator ground wire connec-
tion at engine (if equipped). They should all be clean
and tight. Repair as required.
SPECIFICATIONS
GENERATOR RATINGS - GAS POWERED
TYPE PART NUMBER RATED SAE AMPS ENGINES MINIMUM TEST AMPS
BOSCH 56041322 136 4.0L 6-Cylinder 100
DENSO 56041324 136 4.7L V-8 100
TORQUE - GAS POWERED
DESCRIPTION N-m Ft. Lbs. In. Lbs.
Generator Mounting Bolts-4.0L 55 41
Generator Vertical Mounting Bolt-4.7L 40 29
Generator (long) Horizontal Mounting
Bolt-4.7L55 41
Generator (short) Horizontal Mounting
Bolt-4.7L55 41
Generator B+ Terminal Nut 11 95
WJCHARGING 8F - 25
CHARGING (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

HEATED SYSTEMS
TABLE OF CONTENTS
page page
HEATED GLASS........................... 1
HEATED MIRRORS......................... 8HEATED SEAT SYSTEM..................... 9
HEATED GLASS
TABLE OF CONTENTS
page page
HEATED GLASS
DESCRIPTION - REAR WINDOW DEFOGGER . . 1
OPERATION - REAR WINDOW DEFOGGER....2
DIAGNOSIS AND TESTING - REAR WINDOW
DEFOGGER SYSTEM...................2
REAR WINDOW DEFOGGER GRID
DESCRIPTION..........................3
OPERATION............................3
DIAGNOSIS AND TESTING - REAR WINDOW
DEFOGGER GRID......................3
STANDARD PROCEDURE - REAR GLASS
HEATING GRID REPAIR.................4
REAR WINDOW DEFOGGER RELAY
DESCRIPTION..........................5OPERATION............................5
DIAGNOSIS AND TESTING - REAR WINDOW
DEFOGGER RELAY.....................5
REMOVAL.............................6
INSTALLATION..........................6
REAR WINDOW DEFOGGER SWITCH
DESCRIPTION..........................6
OPERATION............................7
DIAGNOSIS AND TESTING - REAR WINDOW
DEFOGGER SWITCH...................7
REMOVAL.............................7
HEATED GLASS
DESCRIPTION - REAR WINDOW DEFOGGER
An electrically heated rear window defogger is
standard factory-installed equipment on this model.
Electrically heated outside rear view mirrors are
available factory-installed optional equipment. When
the rear window defogger system is turned on, elec-
tric heater grids on the liftgate flip-up glass and
behind both outside rear view mirror glasses are
energized. These electric heater grids produce heat to
help clear the rear window glass and the outside rear
view mirrors of ice, snow, or fog. The rear window
defogger system control circuit uses ignition switched
battery current, so the system will only operate when
the ignition switch is in the On position.
This group covers the following components of the
rear window defogger system:
²Rear glass heating grid
²Rear window defogger relay²Rear window defogger switch.
Certain functions and features of the rear window
defogger system rely upon resources shared with
other electronic modules in the vehicle over the Pro-
grammable Communications Interface (PCI) data bus
network. The PCI data bus network allows the shar-
ing of sensor information. This helps to reduce wire
harness complexity, 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 fea-
ture capabilities. For diagnosis of these electronic
modules or of the PCI data bus network, use a
DRBIIItscan tool and (Refer to Appropriate Diagnos-
tic Information).
The other electronic modules that may affect
proper system operation are:
²Body Control Module (BCM)- Refer to Elec-
tronic Control Modules for more information.
²Driver Door Module (DDM)- Refer to Elec-
tronic Control Modules for more information.
WJHEATED SYSTEMS 8G - 1

²Passenger Door Module (PDM)- Refer to
Electronic Control Modules for more information.
OPERATION - REAR WINDOW DEFOGGER
The rear window defogger system is controlled by a
momentary switch that is integral to the a/c heater
control located in the center stack area of the instru-
ment panel. A Light-Emitting Diode (LED) in the
switch button will light to indicate when the rear
window defogger system is turned on. The BCM,
which contains the rear window defogger system
timer and control logic, monitors the status of the
defogger switch through a hard-wired input. The
BCM then sends control outputs through a hard
wired circuit to energize or de-energize the defogger
relay.
The electrically heated outside rear view mirror
heating grids are also controlled by the rear window
defogger switch. When the BCM receives an input
from the switch, it sends a defogger switch status
message to the DDM and the PDM over the PCI data
bus. The DDM and PDM respond to the defogger
switch status messages by energizing or de-energiz-
ing the battery current feed to their respective out-
side rear view mirror heating grids.
The rear window defogger system will be automat-
ically turned off after a programmed time interval of
about ten minutes. After the initial time interval has
expired, if the defogger switch is turned on again
during the same ignition cycle, the defogger system
will automatically turn off after about five minutes.
The defogger system will automatically shut off if the
ignition switch is turned to the Off position, or it can
be turned off manually by depressing the rear win-
dow defogger switch again.
See the owner's manual in the vehicle glove box for
more information on the features, use and operation
of the rear window defogger system.
DIAGNOSIS AND TESTING - REAR WINDOW
DEFOGGER SYSTEM
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.For complete circuit diagrams, (Refer to Appropri-
ate Wiring Information). The operation of the electri-
cally heated rear window defogger system can be
confirmed in one of the following manners:
1. Turn the ignition switch to the On position.
While monitoring the instrument panel voltmeter,
depress the rear window defogger switch to the On
position. When the rear window defogger switch is
turned On, a distinct voltmeter needle deflection
should be noted.
2. Turn the ignition switch to the On position.
Depress the rear window defogger switch to the On
position. The rear window defogger operation can be
checked by feeling the rear window or outside rear
view mirror glass. A distinct difference in tempera-
ture between the grid lines and the adjacent clear
glass or the mirror glass can be detected within three
to four minutes of operation.
3. Using a 12-volt DC voltmeter, contact the rear
glass heating grid terminal A (right side) with the
negative lead, and terminal B (left side) with the pos-
itive lead (Fig. 1). The voltmeter should read battery
voltage.
The above checks will confirm rear window defog-
ger system operation. Illumination of the rear win-
dow defogger switch LED indicator means that there
is battery current available at the output of the rear
window defogger relay, but does not confirm that bat-
tery current is reaching the rear glass heating grid
lines.
If the rear window defogger system does not oper-
ate, the problem should be isolated in the following
manner:
Fig. 1 REAR WINDOW GLASS GRID TEST
1 - TERMINAL ªAº
2 - TERMINAL ªBº
3 - FEED WIRE
4 - MID-POINT ªCº (TYPICAL)
5 - HEATED REAR WINDOW DEFOGGER GRID
6 - GROUND WIRE
8G - 2 HEATED GLASSWJ
HEATED GLASS (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)

not attach the wire harness connectors until the cur-
ing process is complete.
(11) Check the operation of the rear glass heating
grid.
REAR WINDOW DEFOGGER
RELAY
DESCRIPTION
The rear window defogger relay is an electrome-
chanical device that switches fused battery current to
the rear glass heating grid and the Light-Emitting
Diode (LED) indicator of the rear window defogger
switch, when the Body Control Module (BCM) rear
window defogger timer and logic circuitry grounds
the relay coil. The rear window defogger relay is
located in the junction block, under the left end of
the instrument panel in the passenger compartment.
The rear window defogger relay is a International
Standards Organization (ISO) relay. Relays conform-
ing to the ISO specifications have common physical
dimensions, current capacities, terminal patterns,
and terminal functions.
The rear window defogger 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 - REAR WINDOW
DEFOGGER RELAY
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
RELAY TEST
The rear window defogger relay (Fig. 4) is located
in the junction block, under the left end of the instru-
ment panel in the passenger compartment. Remove
the rear window defogger relay from the junction
block to perform the following tests:
(1) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to Step 2. If not OK, replace the faulty relay.
(2) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 75   10 ohms. If OK, go to Step
3. If not OK, replace the faulty relay.
(3) Connect a battery to terminals 85 and 86.
There should now be continuity between terminals
30 and 87, and no continuity between terminals 87A
and 30. If OK, refer to theRelay Circuit Test.If
not OK, replace the faulty relay.
RELAY CIRCUIT TEST
(1) The relay common feed terminal cavity (30) is
connected to battery voltage and should be hot at all
times. If OK, go to Step 2. If not OK, repair the open
fused B(+) circuit to the Power Distribution Center
(PDC) fuse as required.
(2) The relay normally closed terminal (87A) is
connected to terminal 30 in the de-energized position,
but is not used for this application. Go to Step 3.
Fig. 4 REAR WINDOW DEFOGGER RELAY
TERMINAL LEGEND
NUMBER IDENTIFICATION
30 COMMON FEED
85 COIL GROUND
86 COIL BATTERY
87 NORMALLY OPEN
87A NORMALLY CLOSED
WJHEATED GLASS 8G - 5
REAR WINDOW DEFOGGER GRID (Continued)

repaired and, if faulty or damaged, the entire a/c
heater control must be replaced. (Refer to 24 - HEAT-
ING & AIR CONDITIONING/CONTROLS/A/C
HEATER CONTROL - REMOVAL)
OPERATION
When the rear window defogger switch push but-
ton is depressed, it momentarily closes the rear win-
dow defogger switch sense circuit for the BCM to
ground. The BCM monitors the rear window defogger
switch sense circuit. Each time the BCM rear win-
dow defogger timer and logic circuitry sees another
input from the switch, it toggles a control output to
the rear window defogger relay. Energizing the rear
window defogger relay provides electrical current to
the rear window defogger grid and to the LED indi-
cator in the switch, which lights to indicate when the
defogger system is turned on. A dedicated fuse in the
junction block protects the rear window defogger
relay output circuit to the LED indicator.
DIAGNOSIS AND TESTING - REAR WINDOW
DEFOGGER SWITCH
For complete circuit diagrams, refer to the Appro-
priate Wiring Information.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect and isolate the battery negative
cable. Remove the a/c heater control from the instru-
ment panel and disconnect the 11-way (manual tem-
perature control) or 16-way (automatic zone control)
instrument panel wire harness connector from the a/c
heater control receptacle.
(2) Check for continuity between the ground cir-
cuit cavity of the 11-way or 16-way instrument panel
wire harness connector for the a/c heater control 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) Connect two jumper wires to the a/c heater
control 11-way or 16-way connector receptacle. Con-
nect one jumper from the ground circuit terminal inthe 11-way or 16-way a/c heater control connector
receptacle to a good ground. Connect the other
jumper from the fused rear window defogger relay
output circuit terminal of the 11-way or 16-way con-
nector receptacle to a 12-volt battery feed. The rear
window defogger switch LED indicator should light.
If OK, go to Step 4. If not OK, replace the faulty a/c
heater control.
(4) Check for continuity between the ground cir-
cuit and rear window defogger switch sense circuit
terminals of the 11-way or 16-way a/c heater control
connector receptacle. There should be momentary
continuity as the rear window defogger switch push
button is depressed, and then no continuity. If OK, go
to Step 5. If not OK, replace the faulty a/c heater
control.
(5) Disconnect the 22-way instrument panel wire
harness connector from the Body Control Module
(BCM) connector receptacle. Check for continuity
between the rear window defogger switch sense cir-
cuit cavity of the 11-way or 16-way instrument panel
wire harness connector for the a/c heater control and
a good ground. There should be no continuity. If OK,
go to Step 6. If not OK, repair the shorted rear win-
dow defogger switch sense circuit as required.
(6) Check for continuity between the rear window
defogger switch sense circuit cavities of the 11-way or
16-way instrument panel wire harness connector for
the a/c heater control and the 22-way instrument
panel wire harness connector for the BCM. There
should be continuity. If OK, refer to (Refer to 8 -
ELECTRICAL/HEATED GLASS/REAR WINDOW
DEFOGGER RELAY - DIAGNOSIS AND TESTING).
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(Refer to 24 - HEATING & AIR CONDITIONING/
CONTROLS/A/C HEATER CONTROL - REMOVAL)
WJHEATED GLASS 8G - 7
REAR WINDOW DEFOGGER SWITCH (Continued)

HEATED SEAT SYSTEM
TABLE OF CONTENTS
page page
HEATED SEAT SYSTEM
DESCRIPTION..........................9
OPERATION...........................10
DIAGNOSIS AND TESTING - HEATED SEAT
SYSTEM............................10
DRIVER HEATED SEAT SWITCH
DESCRIPTION.........................11
OPERATION...........................11
DIAGNOSIS AND TESTING - DRIVER HEATED
SEAT SWITCH........................11
REMOVAL.............................12
INSTALLATION.........................13
HEATED SEAT ELEMENT
DESCRIPTION.........................13
OPERATION...........................13
DIAGNOSIS AND TESTING - HEATED SEAT
ELEMENT...........................14REMOVAL.............................14
INSTALLATION.........................14
HEATED SEAT SENSOR
DESCRIPTION.........................15
DIAGNOSIS AND TESTING - HEATED SEAT
SENSOR............................15
REMOVAL.............................15
PASSENGER HEATED SEAT SWITCH
DESCRIPTION.........................15
OPERATION...........................16
DIAGNOSIS AND TESTING - PASSENGER
HEATED SEAT SWITCH.................16
REMOVAL.............................17
INSTALLATION.........................17
HEATED SEAT SYSTEM
DESCRIPTION
Individually controlled driver and passenger side
electrically heated front seats are available factory-
installed optional equipment on this model, when it
is also equipped with the power seat option. The
heated seat system allows both the driver and the
front seat passenger the option to select one of two
seat heating ranges, Low or High, or to turn the indi-
vidual seat heaters Off using the heated seat
switches located in the center lower bezel near the
bottom of the instrument panel center stack (Fig. 1).
The heated seat switch circuit operates on ignition
switched battery current supplied through a fuse in
the junction block, only when the ignition switch is
in the On position.
The heated seat system consists of the following
components :
²Heated seat elements
²Heated seat sensors
²Heated seat module (or memory heated seat
module)
²Heated seat switches.
The heated seat system also relies upon resources
shared with other electronic modules in the vehicle
over the Programmable Communications Interface
(PCI) data bus network. The PCI data bus network
allows the sharing of sensor information. This helps
to reduce wire harness complexity, internal controller
hardware, and component sensor current loads. At
the same time, this system provides increased reli-
ability, enhanced diagnostics, and allows the addition
of many new feature capabilities. For diagnosis of
Fig. 1 HEATED SEAT SWITCHES
1 - HEATED SEAT SWITCHES
WJHEATED SEAT SYSTEM 8G - 9

these electronic modules or of the PCI data bus net-
work, the use of a DRBtscan tool and the proper
Diagnostic Procedures manual are recommended.
The electronic modules that may affect heated seat
system operation are as follows:
²Body Control Module (BCM)- Refer toBody
Control Modulein Electronic Control Modules for
more information.
²Heated Seat Module (HSM)- Refer toHeated
Seat Modulein Electronic Control Modules for more
information.
²Memory Heated Seat Module (MHSM)-If
the vehicle is equipped with the Memory System,
refer toMemory Seat Modulein Electronic Control
Modules for more information.
Refer toPower Seats Premium I/IIIin the Con-
tents of Wiring Diagrams for complete circuit dia-
grams. Following are general descriptions of the
major components in the heated seat system.
OPERATION
The heated seat system will only operate when the
ignition switch is in the On position, and the surface
temperature at the front seat heating element sen-
sors is below the designed temperature set points of
the system. The heated seat system will not operate
in ambient temperatures greater than about 41É C
(105É F). The front seat heating elements and sensors
are hard wired to the Heated Seat Module (HSM) or
the Memory Heated Seat Module (MHSM).
The heated seat switches are hard wired to the
Body Control Module (BCM). The BCM monitors the
heated seat switch inputs, then sends heated seat
switch status messages to the HSM or MHSM over
the Programmable Communications Interface (PCI)
data bus. The HSM or MHSM contains the control
logic for the heated seat system. The HSM or MHSM
responds to the heated seat switch status messages,
ignition switch status messages, and the front seat
heating element sensor inputs by controlling the out-
put to the front seat heating elements through inte-
gral solid-state relays.
When a seat heater is turned on, the sensor
located on the seat cushion electric heater element
provides the HSM or MHSM with an input indicating
the surface temperature of the seat cushion. If the
surface temperature input is below the temperature
set point for the selected Low or High heated seat
switch position, the HSM or MHSM energizes the
integral solid-state relay, which supplies battery cur-
rent to the heating elements in the seat cushion and
back. When the sensor input indicates the correct
temperature set point has been achieved, the HSM or
MHSM de-energizes the solid-state relay. The HSM
or MHSM will continue to cycle the solid-state relay
as needed to maintain the temperature set point.The HSM or MHSM and the seat heater elements
operate on non-switched battery current supplied
through the power seat circuit breaker in the junc-
tion block. However, the HSM or MHSM will auto-
matically turn off the heating elements if it detects
an open or short in the sensor circuit, a short or open
in the heating element circuit causing an excessive
current draw, or when the ignition switch is turned
to the Off position.
See the owner's manual in the vehicle glove box for
more information on the features, use and operation
of the heated seat system.
DIAGNOSIS AND TESTING - HEATED SEAT
SYSTEM
Following are tests that will help to diagnose the
components and circuits that are hard wired inputs
or outputs of the heated seat system. However, these
tests may not prove conclusive in the diagnosis of
this system. In order to obtain conclusive testing of
the heated seat system, the Programmable Commu-
nications Interface (PCI) data bus network and all of
the electronic modules that provide inputs to, or
receive outputs from the heated seat system compo-
nents must be checked.
The most reliable, efficient, and accurate means to
diagnose the heated seat system requires the use of a
DRB scan tool and the proper Diagnostic Procedures
manual. The DRBtscan tool can provide confirma-
tion that the PCI data bus is functional, that all of
the electronic modules are sending and receiving the
proper messages on the PCI data bus, and that the
Heated Seat Module (HSM) or Memory Heated Seat
Module (MHSM) is receiving the proper hard wired
inputs and relaying the proper hard wired outputs to
perform its heated seat system functions.
For complete circuit diagrams, refer toWiring
Diagrams.
NOTE: DO NOT ATTEMPT TO SWAP MEMORY OR
NON-MEMORY HEATED SEAT MODULES FROM
ONE VEHICLE TO ANOTHER. MOST OF THESE
MODULES ARE VEHICLE FEATURE SPECIFIC AND
THEREFORE NOT INTERCHANGEABLE. ALWAYS
USE THE CORRECT PART NUMBERED MODULE
WHEN DIAGNOSING OR REPLACING A MODULE.
WARNING: REFER TO THE RESTRAINTS SECTION
OF THIS MANUAL 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.
8G - 10 HEATED SEAT SYSTEMWJ
HEATED SEAT SYSTEM (Continued)