heating DODGE RAM 2002 Service Owner's Guide

OPERATION - HEATED MIRROR SYSTEM
The solid state electronic control logic and timer
circuitry for the heated mirror system receives bat-
tery current from a fuse in the Junction Block (JB)
only when the ignition switch is in the On or Start
positions. After the heated mirror system is turned
On, the electronic control logic and timer circuitry
will automatically turn the system off after a pro-
grammed time interval of about fifteen minutes.
After the initial time interval has expired, if the
heated mirror switch is depressed and released a sec-
ond time during the same ignition cycle, the elec-
tronic control logic and timer circuitry will
automatically turn the heated mirror system off after
a programmed time interval of about five minutes.
The heated mirror system will be shut off automati-
cally if the ignition switch is turned to the Off or
Accessory positions. After the heated mirror system
is turned On, it can also be turned off manually by
depressing and releasing the heated mirror switch a
second time.
When the heated mirror system is turned On, the
heated mirror system control logic and timer cir-
cuitry energizes the heated mirror system indicator
lamp and the heated mirror relay. When energized,
the heated mirror relay supplies fused ignition
switch output (run/start) current from a fuse in the
JB to the outside mirror heating grids located behind
the mirror glass of each of the outside rear view mir-
rors. When energized, each of the outside mirror
heating grids produces enough heat to warm the
glass of the outside rear view mirrors.
DIAGNOSIS AND TESTING - HEATED MIRROR
SYSTEM
If only one of the outside mirror heating grids is
inoperative, perform continuity checks on the circuits
and heater grid for that mirror only. If both outside
mirror heating grids are inoperative, proceed with
the heated mirror system diagnosis as follows. (Refer
to Appropriate 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 ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.The operation of the heated mirror system can be
confirmed in one of the following manners:
²Turn the ignition switch to the On position.
While monitoring the instrument panel voltmeter,
momentarily depress and release the heated mirror
switch. When the heated mirror system is turned On,
a distinct voltmeter needle deflection should be
noted.
²Turn the ignition switch to the On position.
Momentarily depress and release the heated mirror
switch to turn the heated mirror system On. The
heated mirror operation can be checked by feeling
the outside rear view mirror glass. A distinct differ-
ence in temperature between the unheated and
heated mirror glass can be detected within three to
four minutes of system operation.
The above checks will confirm system operation.
Illumination of the heated mirror system indicator
lamp means that there is electrical current available
at the heated mirror relay, but does not confirm that
the electrical current is reaching the outside mirror
heating grids.
If the heated mirror system does not operate, the
problem should be isolated in the following manner:
(1) Confirm that the ignition switch is in the On
position.
(2) Check the fuses in the Power Distribution Cen-
ter (PDC) and in the Junction Block (JB). The fuses
must be tight in their receptacles and all electrical
connections must be secure.
When the above steps have been completed and
both outside mirror heating grids are still inopera-
tive, one or more of the following is faulty:
²Heated mirror switch, electronic control logic
and timer circuitry, and heated mirror relay.
²Heated mirror wire harness circuits or connec-
tors.
²Outside mirror heating grid (both mirror grids
would have to be faulty).
If turning On the heated mirror system produces a
severe voltmeter deflection or fuse failures, check for
a shorted circuit between the output of the heated
mirror relay and the outside mirror heating grids.
MIRROR SWITCH
DESCRIPTION
The heated mirror switch, the heated mirror sys-
tem indicator lamp, the heated mirror system solid
state electronic control logic and timer circuitry and
the heated mirror relay are all integral to the a/c
heater control, which is located between the instru-
ment cluster and the radio near the center of the
instrument cluster bezel on the instrument panel.
The heated mirror switch and the heated mirror sys-
8G - 2 HEATED MIRRORSBR/BE
HEATED MIRRORS (Continued)

tem indicator lamp are visible in the lower left corner
of the a/c heater control face plate (Fig. 2).
The heated mirror switch, the heated mirror sys-
tem indicator lamp, the heated mirror system solid
state electronic control logic and timer circuitry and
the heated mirror relay cannot be repaired. If any of
these components is damaged or faulty, the entire a/c
heater control must be replaced. (Refer to 24 - HEAT-
ING & AIR CONDITIONING/CONTROLS/A/C
HEATER CONTROL - REMOVAL)
OPERATION
The momentary-type heated mirror switch provides
a hard-wired battery current signal to the heated
mirror system electronic control logic circuitry each
time it is depressed. In response to the heated mirror
switch input, the electronic control logic and timer
circuitry energizes or de-energizes the amber heated
mirror system indicator lamp next to the heated mir-
ror switch to indicate that the heated mirror system
is turned On or Off. The electronic control logic and
timer circuitry also energizes or de-energizes the
heated mirror relay, which controls the feed of elec-
trical current to the outside mirror heating grids.
The heated mirror system electronic control logic
and timer circuitry is programmed to turn the heated
mirror system Off automatically after about fifteen
minutes of operation. If the heated mirror system is
turned On a second time following an initial time-out
event during the same ignition switch cycle, the
heated mirror system electronic control logic and
timer circuit is programmed to turn the system Offautomatically after about five minutes. When the
electronic control logic and timer circuit detects that
a programmed time interval has elapsed, it will auto-
matically de-energize the heated mirror system indi-
cator lamp and the heated mirror relay. The heated
mirror system will also be turned Off if the heated
mirror switch is depressed while the system is
turned On, or if the ignition switch is turned to the
Off or Accessory positions.
DIAGNOSIS AND TESTING - HEATED MIRROR
SWITCH
The heated mirror switch, the solid state electronic
heated mirror system control logic and timer cir-
cuitry, the heated mirror system indicator lamp and
the heated mirror relay are all integral to the a/c
heater control. For circuit descriptions and diagrams
(Refer to Appropriate 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 ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Check the fused ignition switch output (run/
start) fuse in the Junction Block (JB). If OK, go to
Step 2. If not OK, repair the shorted circuit or com-
ponent as required and replace the faulty fuse.
(2) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (run/start) fuse in the JB. If OK, go to Step 3.
If not OK, repair the open circuit to the ignition
switch as required.
(3) Disconnect and isolate the battery negative
cable. Disconnect the 3-way instrument panel wire
harness connector for the heated mirror switch from
the heated mirror switch connector receptacle on the
back of the a/c heater control. Check for continuity
between the ground circuit cavity of the wire harness
connector and a good ground. There should be conti-
nuity. If OK, go to Step 4. If not OK, repair the open
ground circuit to ground as required.
(4) Reconnect the battery negative cable. Turn the
ignition switch to the On position. Check for battery
voltage at the fused ignition switch output (run/start)
circuit cavity of the 3-way instrument panel wire
Fig. 2 HEATED MIRROR SWITCH
1 - A/C HEATER CONTROL
2 - HEATED MIRROR SWITCH
3 - HEATED MIRROR SYSTEM INDICATOR LAMP
BR/BEHEATED MIRRORS 8G - 3
MIRROR SWITCH (Continued)

harness connector for the heated mirror switch. If
OK, go to Step 5. If not OK, repair the open fused
ignition switch output (run/start) circuit to the fuse
in the JB as required.
(5) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Reconnect the 3-way instrument panel wire harness
connector for the heated mirror switch to the heated
mirror switch connector receptacle on the back of the
a/c heater control. Reconnect the battery negative
cable. Turn the ignition switch to the On position.
Depress and release the heated mirror switch. The
amber heated mirror system indicator lamp next to
the heated mirror switch button should light. If OK,
go to Step 6. If not OK, replace the faulty a/c heater
control.
(6) Back probe the fused heated mirror relay out-
put circuit cavity of the 3-way instrument panel wire
harness connector for the heated mirror switch on
the back of the a/c heater control and check for volt-
age (battery voltage less the resistance in both out-
side mirror heating grids). If OK, (Refer to 8 -
ELECTRICAL/HEATED MIRRORS/HEATED MIR-
ROR GRID - DIAGNOSIS AND TESTING).
HEATED MIRROR GRID
DESCRIPTION
Vehicles equipped with the optional heated mirror
system have an electrically operated heating grid
located behind the mirror glass of each power oper-
ated outside rear view mirror. The outside mirror
heating grid consists of two thin laminations of plas-
tic that approximate the outer dimensions and shape
of the mirror glass. A single length of resistor wire
weaves in a back and forth pattern between, and is
held in place by the two thin laminations of plastic.
The two ends of the resistor wire terminate near the
inboard edge of the grid, where they are soldered to
the ground feed and battery current feed wires con-
tained in the power mirror wire harness. The heating
grid is then sandwiched between the back of the
molded plastic mirror glass case and the mirror
glass, where it remains in direct contact with the
back of the mirror glass at all times.
The outside mirror heating grids cannot be
repaired and, if faulty or damaged, the entire outside
power mirror unit must be replaced. Refer to Power
Mirrors for the service procedures.
OPERATION
One end of the outside mirror heating grid resistor
wire is connected to a ground feed at all times
through a body ground screw located inside the left
rear corner of the truck cab. Battery current is
directed to the other end of the outside mirror heat-
ing grid resistor wire by the energized heated mirror
relay when the heated mirror switch is in the On
position. As electrical current passes through the
heating grid, the resistance of the wire in the heating
grid converts some of that electrical current into
heat. The heat produced by the heating grid is then
conducted through the back of the mirror glass to
help keep the glass clear of ice, snow or fog.
DIAGNOSIS AND TESTING - HEATED MIRROR
GRID
For circuit descriptions and diagrams (Refer to
Appropriate Wiring Information).
(1) Disconnect and isolate the battery negative
cable. Disconnect the door wire harness connector
from the power mirror wire harness connector at the
power mirror with the inoperative heating grid.
Check for continuity between the ground circuit cav-
ity in the door wire harness connector for the power
mirror and a good ground. If OK, go to Step 2. If not
OK, repair the open ground circuit to ground as
required.
(2) Reconnect the battery negative cable. Turn the
ignition switch to the On position. Turn on the
heated mirror system. Check for voltage (battery
voltage less the resistance in the outside mirror heat-
ing grid that is still connected) at the fused heated
mirror relay output circuit cavity in the door wire
harness connector for the power mirror. If OK, go to
Step 3. If not OK, repair the open fused heated mir-
ror relay output circuit to the heater and air condi-
tioner control unit as required.
(3) Check the outside mirror heating grid by test-
ing for continuity between the ground circuit and the
fused heated mirror relay output circuit cavities in
the power mirror wire harness connector. There
should be continuity. If not OK, replace the faulty
power mirror. If OK, check the resistance through
the outside mirror heating grid. The correct resis-
tance should be from 10 to 16 ohms when measured
at an ambient temperature of 21É C (70É F). If not
OK, replace the faulty power mirror.
8G - 4 HEATED MIRRORSBR/BE
MIRROR SWITCH (Continued)

HEATED SEAT SYSTEM
TABLE OF CONTENTS
page page
HEATED SEAT SYSTEM
DESCRIPTION..........................5
OPERATION............................6
DIAGNOSIS AND TESTING - HEATED SEAT
SYSTEM.............................6
DRIVER SEAT HEATER SWITCH
DESCRIPTION..........................7
OPERATION............................8
DIAGNOSIS AND TESTING - HEATED SEAT
SWITCH.............................8
REMOVAL.............................9
INSTALLATION.........................10
HEATED SEAT ELEMENT
DESCRIPTION.........................10
OPERATION...........................11
DIAGNOSIS AND TESTING - HEATED SEAT
ELEMENT AND SENSOR................11REMOVAL.............................13
INSTALLATION.........................13
HEATED SEAT RELAY
DESCRIPTION.........................14
OPERATION...........................15
DIAGNOSIS AND TESTING - HEATED SEAT
RELAY..............................15
REMOVAL.............................16
INSTALLATION.........................16
PASSENGER SEAT HEATER SWITCH
DESCRIPTION.........................16
OPERATION...........................17
DIAGNOSIS AND TESTING - HEATED SEAT
SWITCH............................17
REMOVAL.............................18
INSTALLATION.........................19
HEATED SEAT SYSTEM
DESCRIPTION
Individually controlled electrically heated front
seats are available factory-installed optional equip-
ment on the Ram quad cab models that are also
equipped with the optional SLT Plus (leather) trim
package. Vehicles with this option can be visually
identified by the two separate heated seat switches
mounted in a bezel located in the lower right corner
of the instrument cluster bezel, next to the radio
receiver (Fig. 1). The heated seat system allows the
front seat driver and passenger to select from two
different levels of supplemental electrical seat heat-
ing, or no seat heating to suit their individual com-
fort requirements. The heated seat system for this
vehicle includes the following major components,
which are described in further detail later in this sec-
tion:
²Heated Seat Switches- Two heated seat
switches are used per vehicle, including two Light-
Emitting Diode (LED) indicator lamps and an incan-
descent back lighting bulb for each switch. One
switch for the driver and one for the passenger front
seats. The switches are mounted in the instrument
panel, next to the radio.
²Heated Seat Module- also referred to as the
Seat Heat Interface Module (SHIM), this module con-
tains the solid state electronic control and diagnostic
logic circuitry for the heated seat system. One heated
seat module is used per vehicle and is mounted
under the center front seat cushion. Refer to the
Electronic Control Modules section of the service
manual for heated seat module information.
Fig. 1 Heated Seat System Switches
1 - Radio Receiver
2 - Heated Seat Switches
BR/BEHEATED SEAT SYSTEM 8G - 5

²Heated Seat Elements- Four heated seat ele-
ments are used per vehicle, one for each front seat
back and one for each front seat cushion. The ele-
ments are integral to the individual front seat and
seat back cushions and cannot be removed once
installed at the factory. Service replacement seat
heating elements are available, without having to
replace the entire seat cushion or trim cover. Refer to
the procedure in this section.
²Heated Seat Sensors- Two heated seat sen-
sors are used per vehicle, one for each front seat. The
sensors are integral to the individual front seat heat-
ing elements and cannot be removed once installed at
the factory. Service replacement seat heating ele-
ments with the sensors are available, without having
to replace the entire seat cushion or trim cover. Refer
to the procedure in this section.
²Heated Seat Relay- The heated seat relay
controls the battery voltage and current supply to the
heated seat module and the rest of the heated seat
system. The heated seat relay is mounted in the
junction block and is not different than the other
relays used throughout the vehicle. Refer to the
Power Distribution section of the service manual for
more information on standard ISO relays.
Following are general descriptions of the major
components in the heated seat system. See the own-
er's manual in the vehicle glove box for more infor-
mation on the features, use and operation of the
heated seat system. Refer toWiring Diagramsfor
the location of complete heated seat system wiring
diagrams.
OPERATION
The heated seat module receives fused battery cur-
rent through the energized heated seat relay in the
Junction Block (JB) only when the engine is running.
The heated seat switches receive battery current
through fuse #2 in the Junction Block only when the
ignition switch is in the On position. The heated seat
module shares a common ground circuit with each of
the heated seat elements. The heated seat elements
will only operate when the surface temperature of
the seat cushion is below the designed temperature
set points of the system.
The heated seat system will also be turned off
automatically whenever the ignition switch is turned
to any position except On or if the engine quits run-
ning. If the ignition switch is turned to the Off posi-
tion or if the engine quits running while a heated
seat is turned ON, the heated seat will remain Off
after the engine is restarted until a heated seat
switch is depressed again.
The heated seat module monitors inputs from the
heated seat sensors and the heated seat switches. In
response to these inputs the heated seat module usesits internal programming to control outputs to the
heated seat elements in both front seats and to con-
trol the heated seat LED indicator lamps located in
both of the heated seat switches. The heated seat
module is also programmed to provide a self-diagnos-
tic capability. When the module detects certain fail-
ures within the heated seat system, it will provide a
visual indication of the failure by flashing the indica-
tor lamps in the heated seat switches. The heated
seat module will automatically turn off the heated
seat elements if it detects a short or open in the
heated seat element circuit or a heated seat sensor
value that is out of range.
DIAGNOSIS AND TESTING - HEATED SEAT
SYSTEM
HEATED SEAT SYSTEM SELF-DIAGNOSIS
The heated seat system is capable of performing
some self-diagnostics. The following table depicts the
various monitored failures which will be reported to
the vehicle operator or technician by flashing the
individual heated seat switch Light Emitting Diode
(LED) indicator lamps. Refer to the Heated Seat Sys-
tem Self-Diagnosis table for failure identification.
The driver side heated seat switch indicator lamps
will flash if a failure occurs in the driver side heated
seat, and the passenger side heated seat switch indi-
cator lamps will flash for a passenger side heated
seat failure. If a monitored heated seat system fail-
ure occurs, the switch indicator lamps will flash at a
pulse rate of about one-half second on, followed by
about one-half second off for a duration of about one
minute after the switch for the faulty heated seat is
depressed in either the Low or High direction. This
process will repeat every time the faulty heated seat
switch is actuated until the problem has been cor-
rected.
Heated Seat System Self-Diagnosis
Monitored FailureSwitch High
Indicator LampSwitch Low
Indicator Lamp
Heated Seat
Element ShortedFlashing Flashing
Heated Seat
Element OpenFlashing Off
Heated Seat
Sensor Value Out
of RangeOff Flashing
8G - 6 HEATED SEAT SYSTEMBR/BE
HEATED SEAT SYSTEM (Continued)

tor receptacles on the switches so that the two
heated seat switches can only be connected to the
proper heated seat electrical.
The momentary, bidirectional rocker-type heated
seat switch provides a resistor-multiplexed signal to
the heated seat module on the mux circuit. Each
switch has a center neutral position and momentary
Low and High positions so that both the driver and
the front seat passenger can select a preferred level
of seat heating. Each heated seat switch has two
Light-Emitting Diode (LED) indicator lamps, which
indicate the selected mode (Low or High) of the seat
heater. These indicator lamps also provide diagnostic
feedback for the heated seat system. Each switch
also has an incandescent bulb, which provides dim-
mer controlled back lighting of the switch when the
headlamps or park lamps are on.
The two LED indicator lamps and the incandescent
bulb in each heated seat switch cannot be repaired. If
the indicator lamps or back lighting bulb are faulty
or damaged, the individual heated seat switch must
be replaced.
OPERATION
The heated seat switches receive battery current
through a fused ignition switch output (run) circuit
when the ignition switch is in the On position.
Depressing the heated seat switch rocker to its
momentary High or Low position provides a hard-
wired resistor multiplexed voltage request signal to
the heated seat module to power the heated seat ele-
ment of the selected seat and maintain the requested
temperature setting. If the heated seat switch is
depressed to a different position (Low or High) than
the currently selected state, the heated seat module
will change states to support the new selection. If a
heated seat switch is depressed a second time to the
same position as the currently selected state, the
heated seat module interprets the second input as a
request to turn the seat heater off. The heated seat
module will then turn the heated seat elements for
that seat off.
The indicator lamps in the heated seat switches
receive battery current through a fused ignition
switch output (run) circuit when the ignition switch
is in the On position. The ground side of each indi-
cator lamp is controlled by a separate (high or low/
driver or passenger) indicator lamp driver circuit by
the heated seat module. The heated seat module con-
trol of the switch indicator lamps also allows the
module to provide diagnostic feedback to the vehicle
operator to indicate monitored heated seat system
faults by flashing the indicator lamps on and off. One
side of the incandescent back lighting bulb in each
heated seat switch is connected to ground at all
times. The other side of the incandescent bulb is con-nected to the fused panel lamps dimmer switch sig-
nal circuit. These bulbs are energized when the park
lamps or headlamps are turned on, and their illumi-
nation intensity is controlled by the panel lamps dim-
mer switch.
DIAGNOSIS AND TESTING - HEATED SEAT
SWITCH
Refer toWiring Diagramsfor the location of com-
plete heated seat system wiring diagrams.
WARNING: DISABLE THE AIRBAG SYSTEM
BEFORE ATTEMPTING ANY STEERING WHEEL,
STEERING COLUMN, OR INSTRUMENT PANEL
COMPONENT DIAGNOSIS OR SERVICE. DISCON-
NECT AND ISOLATE THE BATTERY NEGATIVE
(GROUND) CABLE, THEN WAIT TWO MINUTES FOR
THE AIRBAG SYSTEM CAPACITOR TO DISCHARGE
BEFORE PERFORMING FURTHER DIAGNOSIS OR
SERVICE. THIS IS THE ONLY SURE WAY TO DIS-
ABLE THE AIRBAG SYSTEM. FAILURE TO TAKE
THE PROPER PRECAUTIONS COULD RESULT IN
ACCIDENTAL AIRBAG DEPLOYMENT AND POSSI-
BLE PERSONAL INJURY.
(1) If the problem being diagnosed involves inoper-
ative heated seat switch back lighting and the cluster
illumination lamps operate, go to Step 2. If the prob-
lem being diagnosed involves inoperative heated seat
switch back lighting and the cluster illumination
lamps are also inoperative, refer toInstrument
Clusterin the index of this service manual for the
proper cluster illumination lamps diagnosis and test-
ing procedures. If the problem being diagnosed
involves inoperative heated seat switch indicator
lamps and the heated seat elements do not heat,
refer to Step 4. If the problem being diagnosed
involves inoperative heated seat switch indicator
lamps and the heated seat elements do heat, go to
Step 8. If the problem being diagnosed involves a
heated seat switch indicator lamp that remains illu-
minated after the heated seat has been turned Off,
refer toHeated Seat Modulein Electronic Control
Modules for the location of the proper heated seat
module diagnosis and testing procedures. Also refer
to the Body Diagnostic Manual for additional diagno-
sis and testing procedures.
(2) Disconnect and isolate the battery negative
cable. Remove the heated seat switch and bezel unit
from the instrument panel. Disconnect the instru-
ment panel wire harness connector from the connec-
tor receptacle on the back of the heated seat switch
to be tested. Check for continuity between the ground
circuit cavity of the instrument panel wire harness
connector for the heated seat switch and a good
ground. There should be continuity. If OK, go to Step
8G - 8 HEATED SEAT SYSTEMBR/BE
DRIVER SEAT HEATER SWITCH (Continued)

(6) From the back of the heated seat switch bezel,
gently push the heated seat switch out through the
front of the bezel.
INSTALLATION
Both heated seat switches and the heated seat
switch bezel are available individually for service
replacement.
NOTE: When installing the heated seat switches, be
certain they are installed in the proper mounting
holes of the heated seat switch bezel. Note that the
driver side and passenger side switches are identi-
cal in appearance except for the keyway in the con-
nector receptacle on the backs of the switches. The
driver side switch has the keyway located near the
bottom of the connector receptacle and should be
installed in the left mounting hole of the heated
seat switch bezel. The passenger side switch has
the keyway located near the top of the connector
receptacle and should be installed in the right
mounting hole of the heated seat switch bezel.
(1) From the front of the heated seat switch bezel,
align the back of the heated seat switch with the
proper mounting hole in the heated seat switch bezel
and gently push the switch into the bezel until it
snaps into place.
(2) Position the heated seat switch bezel and both
switches to the instrument panel as a unit.
(3) Reconnect the two instrument panel wire har-
ness connectors to the connector receptacles on the
backs of the heated seat switches.(4) Position the heated seat switch bezel and both
switches in the instrument panel mounting hole as a
unit.
(5) Install and tighten the three screws that secure
the heated seat switch bezel to the instrument panel.
Tighten the screws to 2.2 N´m (20 in. lbs.).
(6) Install the cluster bezel onto the instrument
panel. Refer toCluster Bezelin the index of this
service manual for the location of the proper cluster
bezel installation procedures.
(7) Reconnect the battery negative cable.
HEATED SEAT ELEMENT
DESCRIPTION
Vehicles equipped with the optional heated seat
system have two sets of electrically operated heating
element grids located in each front seat, one set for
the seat cushion and the other set for the seat back.
Each of the heated seat element grids consists of a
single length of resistor wire that is routed in a zig-
zag pattern and captured between a covering and the
adhesive foam rubber backing. Short pigtail wires
with connectors (Fig. 5) are soldered to each end of
each resistor wire element grid, which connect all of
the element grids for each seating position to each
other in series with the heated seat module through
the seat wire harness.
Fig. 4 Heated Seat Switch and Bezel Remove/Install
1 - INSTRUMENT PANEL
2 - SCREW (3)
3 - HEATED SEAT SWITCHES AND BEZEL UNIT
Fig. 5 HEATING ELEMENT INSTALLED
1 - SEAT BACK WIRE HARNESS
2 - HEATED SEAT WIRE HARNESS CONNECTOR
3 - HEATED SEAT CUSHION ELEMENT
8G - 10 HEATED SEAT SYSTEMBR/BE
DRIVER SEAT HEATER SWITCH (Continued)

One temperature sensor is used for each outboard
seating position of the front seat, and it is located in
the center insert area of the seat cushion cover. The
heated seat sensors and their pigtail wires are also
captured between a covering and the adhesive foam
rubber backing. The heated seat sensors are Nega-
tive Thermal Coefficient (NTC) thermistors. The sen-
sors for both front seats receive a voltage feed from a
single output of the heated seat module, but the mod-
ule receives individual sensor inputs from the driver
side and passenger side sensors.
The heated seat elements and sensors should not
be repaired. If damaged or faulty, the heated seat ele-
ment assembly must be replaced. (Refer to 8 - ELEC-
TRICAL/HEATED SEATS/HEATED SEAT
ELEMENT - REMOVAL).
OPERATION
One end of the heated seat element resistor wire is
connected to a ground feed at all times through a
splice in the heated seat module ground circuit. Bat-
tery current is directed to the other end of the heated
seat element resistor wire by the energized N-chan-
nel Field Effect Transistor (N-FET) located within
the heated seat module. The heated seat module will
energize the N-FET only when the heated seat
switch is in the Low or High position and the heated
seat sensor indicates that the seat cushion surface
temperature is below the selected (Low or High) tem-
perature set point. As electrical current passes
through the heating element grid, the resistance of
the wire used in the element disperses some of that
electrical current in the form of heat. The heat pro-
duced by the heated seat element grid then radiates
through the underside of the seat cushion and seat
back trim covers, warming the seat cover and its
occupant.
The resistance of the heated seat sensor increases
and decreases as the surface temperature of the seat
cushion cover changes. The heated seat module sup-
plies each sensor with a voltage feed, then detects
the sensor resistance by monitoring the voltage of the
separate sensor return circuits. The heated seat mod-
ule compares the heated seat sensor resistance (seat
cushion surface temperature) with the heated seat
switch resistance (Low or High set point) to deter-
mine when the heated seat element grids need to be
cycled on or off in order to maintain the selected tem-
perature set point.
DIAGNOSIS AND TESTING - HEATED SEAT
ELEMENT AND SENSOR
The heated seat module will self-diagnose shorted
or open heated seat element circuits and sensor cir-
cuits. Refer to Heated Seat System Diagnosis and
Testing in this section for additional diagnosis and
testing procedures. To manually check the heated
seat element and sensor circuits, proceed as follows.
The wire harness connectors for the seat cushion and
seat back heating elements and sensor are located
under the seat, near the rear edge of the seat cush-
ion frame (Fig. 6) . Refer toWiring Diagramsfor
the location of complete heated seat system wiring
diagrams.
HEATED SEAT ELEMENTS
(1) Position the appropriate seat in the full for-
ward position.
(2) Make certain the ignition switch is in the OFF
position.
Fig. 6 PASSENGER SEAT WIRE HARNESS
ROUTING
1 - SEAT BACK HEATED SEAT WIRE HARNESS
2 - PASSENGER SEAT BACK
3 - SEAT BACK ELEMENT CONNECTOR
4 - SEAT CUSHION ELEMENT CONNECTOR
BR/BEHEATED SEAT SYSTEM 8G - 11
HEATED SEAT ELEMENT (Continued)

(3) Using small channel locks, disengage the seat
cushion trim cover J-channel from the lower seat
cushion frame (Fig. 7).
(4) Disconnect the 2-way heated seat element con-
nector which requires testing (Fig. 7) or (Fig. 8)
Check for continuity between the two heated seat
element circuit cavities (Fig. 9). There should be con-
tinuity. If OK, the elements within the seat assembly
test OK, go to Step 5. If not OK, replace the faulty
seat heating element refer to the procedure in this
section.
(5) Test the seat wire harness between the heated
seat module connector and the appropriate 2-way
heated seat wire harness connector for shorted or
open circuits. If OK, element are OK, proceed with
testing the heated seat sensor and module. If not OK,
repair the shorted or open seat wire harness as
required.
HEATED SEAT SENSOR
NOTE: ANY RESISTANCE VALUES (OHMSV) GIVEN
IN THE FOLLOWING TEXT ARE SUPPLIED USING
THE AUTOMATIC RANGE GENERATED BY A
FLUKETAUTOMOTIVE METER. IF ANOTHER TYPE
OF MEASURING DEVICE IS USED THE VALUES
GENERATED MAY NOT BE THE SAME AS THE
RESULTS SHOWN HERE, OR MAY HAVE TO BE
CONVERTED TO THE RANGE USED HERE.
Fig. 7 DRIVERS SEAT CONNECTORS
1 - DRIVER SEAT BACK TRIM COVER
2 - SEAT BACK ELEMENT CONNECTOR
3 - SEAT CUSHION ELEMENT CONNECTOR
Fig. 8 PASSENGER SEAT CONNECTORS
1 - PASSENGER SEAT BACK TRIM COVER
2 - SEAT BACK ELEMENT CONNECTOR
3 - SEAT CUSHION ELEMENT CONNECTOR
Fig. 9 ELEMENT CONNECTOR
8G - 12 HEATED SEAT SYSTEMBR/BE
HEATED SEAT ELEMENT (Continued)

(1) Position the appropriate seat in the full for-
ward position.
(2) Make certain the ignition switch is in the OFF
position.
(3) Disconnect the 4-way heated seat wire harness
connector from the seat cushion frame (Fig. 10).
Using an ohmmeter, check the resistance between
the heated seat sensor input circuit cavity and the
heated seat sensor feed circuit cavity in the 4-way
heated seat wire harness connector. The heated seat
sensor resistance should be between 1 kilohm and
100 kilohms. If OK, go to Step 4. If not OK, replace
the faulty seat cushion heating element assembly.
(4) Test the seat wire harness between the heated
seat module connector and the 4-way heated seat
wire harness connector for shorted or open circuits. If
OK, refer toDiagnosis and Testing the Heated
Seat Modulein Electronic Control Modules, for the
proper heated seat module diagnosis and testing pro-
cedures. If not OK, repair the shorted or open heated
seat wire harness as required.
REMOVAL
Do not remove the heating element from the seat
or seat back cushion. The original element is perma-
nently attached to the seat cushions and cannot be
removed without damaging the cushion. The service
replacement heating element is designed to be
applied directly over the original seat heating ele-
ment.
(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) Locate the wires leading from the inoperative
heating element and cut them off flush with the edge
of the original heating element.
INSTALLATION
(1) Peel off the adhesive backing on the back of the
replacement heating element and stick directly over
the original heating element (Fig. 11).
CAUTION: During the installation of the replace-
ment heating element, be careful not to fold or
crease the element assembly. Folds or creases will
cause premature failure.
Fig. 10 HEATED SEAT CONNECTOR
1 - SEAT CUSHION FRAME
2 - HEATED SEAT CONNECTOR
Fig. 11 HEATING ELEMENT INSTALLATION
1 - ORIGINAL (INOPERATIVE) HEATING ELEMENT
2 - REPLACEMENT HEATING ELEMENT
BR/BEHEATED SEAT SYSTEM 8G - 13
HEATED SEAT ELEMENT (Continued)