2001 DODGE RAM Heat

(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
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 themolded 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..................6
HEATED SEAT SYSTEM..................6
DRIVER SEAT HEATER SWITCH
DESCRIPTION............................7
OPERATION.............................7
DIAGNOSIS AND TESTING..................8
HEATED SEAT SWITCH...................8
REMOVAL...............................9
INSTALLATION............................9
HEATED SEAT ELEMENT
DESCRIPTION...........................10
OPERATION.............................10
DIAGNOSIS AND TESTING.................11HEATED SEAT ELEMENT & SENSOR.......11
HEATED SEAT RELAY
DESCRIPTION...........................11
OPERATION.............................12
DIAGNOSIS AND TESTING.................12
HEATED SEAT RELAY...................12
REMOVAL..............................13
INSTALLATION...........................13
PASSENGER SEAT HEATER SWITCH
DESCRIPTION...........................13
OPERATION.............................14
DIAGNOSIS AND TESTING.................14
HEATED SEAT SWITCH..................14
REMOVAL..............................15
INSTALLATION...........................16
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) trimpackage. 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:
²The heated seat switches, including two heated
seat Light-Emitting Diode (LED) indicator lamps and
an incandescent back lighting bulb for each switch.
²The heated seat module, also referred to as the
Seat Heat Interface Module (SHIM), which contains
the solid state electronic control and diagnostic logic
circuitry for the heated seat system. Refer to the
Electronic Control Modules section of the service
manual for heated seat module information.
²The heated seat elements and sensors, which
are integral to the individual front seat cushion and
front seat back trim covers.
²The heated seat relay, which controls the avail-
ability of battery current to the heated seat module
or SHIM.
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 toPower Seatin the
index of this service manual for the location of com-
plete heated seat system wiring diagrams.
Fig. 1 Heated Seat System Switches
1 - RADIO RECEIVER
2 - HEATED SEAT SWITCHES
BR/BEHEATED SEAT SYSTEM 8G - 5

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 a fused ignition switch output (run) circuit
only when the ignition switch is in the On position.
The heated seat module shares a common ground cir-
cuit with each of the heated seat elements. The
heated seat elements will only operate when the sur-
face temperature of the seat cushion cover at the
heated seat sensors is below the designed tempera-
ture set points of the system.
The heated seat module will automatically turn off
the heated seat elements if it detects a short in the
heated seat element circuit or a heated seat sensor
value that is out of range. 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 running. If the ignition switch is
turned to the Off position or if the engine quits run-
ning 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 uses
its 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.
DIAGNOSIS & TESTING - HEATED SEAT
SYSTEM
SELF-DIAGNOSIS
The heated seat system is capable of performing
some self-diagnostics. The following table depicts the
various failure modes which will be reported to the
vehicle operator or technician by flashing the individ-
ual heated seat switch Light Emitting Diode (LED)
indicator lamps. See the Heated Seat System Self-Di-
agnosis table for the diagnostic routines. 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 indicator lamps
will flash for a passenger side heated seat failure. If
a monitored heated seat system failure 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 afterthe 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 corrected.
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
TESTING
Refer toPower Seatin the index of this service
manual for the location of complete heated seat sys-
tem wiring diagrams. Before testing the individual
components in the heated seat system, perform the
following preliminary checks:
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.
²If the heated seat switch back lighting and the
cluster illumination lamps do not illuminate with the
headlamps or park lamps turned On, refer toInstru-
ment Clusterin the index of this service manual for
the location of the proper cluster illumination lamps
diagnosis and testing procedures. If the heated seat
switch back lighting does not illuminate, but the
cluster illumination lamps do illuminate with the
headlamps or park lamps turned On, refer to
Heated Seat Switchin this section for the location
of the proper heated seat switch diagnosis and test-
ing procedure.
²If a single indicator lamp for one heated seat
switch does not operate and the heated seat elements
do heat, refer toHeated Seat Switchin this section
for the location of the proper heated seat switch diag-
nosis and testing procedure.
8G - 6 HEATED SEAT SYSTEMBR/BE
HEATED SEAT SYSTEM (Continued)

²If both indicator lamps for a heated seat switch
operate, but the heated seat elements do not heat,
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.
²If none of the indicator lamps for both heated
seat switches will operate and the heated seat ele-
ments for both seats do not heat, refer toHeated
Seat Relayin this section for the location of the
proper heated seat relay diagnosis and testing proce-
dures.
²If the an indicator lamp on either heated seat
switch remains illuminated 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 pro-
cedures. Also refer to the Body Diagnostic Manual for
additional diagnosis and testing procedures.
DRIVER SEAT HEATER
SWITCH
DESCRIPTION
The heated seat switches used on vehicles with
this option are both mounted in a heated seat switch
bezel (Fig. 2), which replaces the standard equipmentcubby bin located in the lower right corner of the
instrument cluster bezel next to the radio receiver.
The two switches are snapped into the mounting
holes of the heated seat switch bezel, and the heated
seat switch bezel is secured with three screws to the
instrument panel. The mounts for the heated seat
switch bezel are concealed behind the instrument
cluster bezel. The two heated seat switches are iden-
tical in appearance and construction, except for the
location of a keyway in the single connector recepta-
cle on the back of each switch. The instrument panel
wire harness connectors for the heated seat switches
are keyed to match the connector receptacles on the
switches so that the two heated seat switches can
only be connected to the proper heated seat.
The momentary, bidirectional rocker-type heated
seat switch provides a resistor-multiplexed signal to
the heated seat module. Each switch has a center
neutral position and momentary Low and High posi-
tions so that both the driver and the front seat pas-
senger can select a preferred seat heating mode.
Each heated seat switch has two Light-Emitting
Diode (LED) indicator lamps, which indicate the
selected mode (Low or High) of the seat heater for
each seat and to provide diagnostic feedback for the
heated seat system. Each switch also has an incan-
descent bulb, which provides panel lamps dimmer
controlled back lighting of the switch nomenclature
when the headlamps or park lamps are turned 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 unit
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.
Fig. 2 Heated Seat Switches
1 - DRIVER SIDE SWITCH
2 - PASSENGER SIDE SWITCH
3 - INDICATOR LAMPS
4 - HEATED SEAT SWITCH BEZEL
BR/BEHEATED SEAT SYSTEM 8G - 7
HEATED SEAT SYSTEM (Continued)

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 & TESTING - HEATED SEAT
SWITCH
Refer toWiring Diagramsfor the location of com-
plete heated seat system wiring diagrams.
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) 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
3. If not OK, repair the open ground circuit to ground
as required.
(3) Reconnect the battery negative cable. Turn the
park lamps on with the headlamp switch. Rotate the
panel lamps dimmer thumbwheel on the headlamp
switch upward to just before the interior lamps
detent. Check for battery voltage at the fused panel
lamps dimmer switch signal circuit cavity of the
instrument panel wire harness connector for the
heated seat switch. If OK, replace the faulty heated
seat switch. If not OK, repair the open fused panel
lamps dimmer switch signal circuit to the fuse in the
Junction Block (JB) as required.
(4) Check the fused ignition switch output (run)
fuse in the Junction Block (JB). If OK, go to Step 5.
If not OK, repair the shorted circuit or component as
required and replace the faulty fuse.
(5) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (run) fuse in the JB. If OK, go to Step 6. If
not OK, repair the open fused ignition switch output
(run) circuit to the ignition switch as required.
(6) 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. Reconnect the battery negative cable.
Turn the ignition switch to the On position. Check
for battery voltage at the fused ignition switch out-
put (run) circuit cavity of the instrument panel wire
harness connector for the heated seat switch. If OK,
go to Step 7. If not OK, repair the open fused ignition
switch output (run) circuit to the JB fuse as required.
(7) Check the continuity and resistance values of
the heated seat switch in the Neutral, Low and High
positions as shown in the Heated Seat Switch Conti-
nuity chart (Fig. 3). If OK, refer toHeated Seat
Modulein Electronic Control Modules for the loca-
tion of the proper heated seat module diagnosis and
testing procedures. Also refer to the Body Diagnostic
8G - 8 HEATED SEAT SYSTEMBR/BE
DRIVER SEAT HEATER SWITCH (Continued)

Manual for additional diagnosis and testing proce-
dures. If not OK, replace the faulty heated seat
switch.
Heated Seat Switch Continuity
Switch PositionContinuity
BetweenResistance
Neutral 4 & 6 2.2 Kilohms
Low 4 & 6 510 Ohms
High 4 & 6 33 Ohms
(8) Replace the inoperative heated seat switch
with a known good unit and test the operation of the
switch indicator lamps. If OK, discard the faulty
heated seat switch. If not OK, refer toHeated Seat
Modulein Electronic Control Modules for the loca-
tion of the proper heated seat module diagnosis and
testing procedures. Also refer to the Body Diagnostic
Manual for additional diagnosis and testing proce-
dures.
REMOVAL
Both heated seat switches and the heated seat
switch bezel are available individually for service
replacement.
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the cluster bezel from the instrument
panel. Refer toCluster Bezelin the index of this
service manual for the location of the proper cluster
bezel removal procedures.
(3) Remove the three screws that secure the
heated seat switch bezel to the instrument panel
(Fig. 4).
(4) Pull the heated seat switch bezel out from the
instrument panel far enough to access and disconnect
the two instrument panel wire harness connectors
from the connector receptacles on the backs of the
heated seat switches.(5) Remove the heated seat switch bezel and both
switches from the instrument panel as a unit.
(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.
Fig. 3 Heated Seat SwitchFig. 4 Heated Seat Switch and Bezel Remove/Install
1 - INSTRUMENT PANEL
2 - SCREW (3)
3 - HEATED SEAT SWITCHES AND BEZEL UNIT
BR/BEHEATED SEAT SYSTEM 8G - 9
DRIVER SEAT HEATER SWITCH (Continued)

(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 outboard seating posi-
tion of the 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 zigzag pattern and
captured between the leather trim cover and the
foam rubber backing on the underside of its respec-
tive seat cushion trim cover and seat back trim cover
assembly. Short pigtail wires with connectors (Fig. 5)
are soldered to each end of each resistor wire ele-
ment grid, which connect all of the element grids foreach seating position to each other in series with the
heated seat module through the seat wire harness.
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 the leather trim cover and the
foam rubber backing on the underside of their
respective seat cushion trim cover assemblies. The
heated seat sensors are Negative Thermal Coefficient
(NTC) thermistors. The sensors for both front seats
receive a voltage feed from a single output of the
heated seat module, but the module receives individ-
ual sensor inputs from the driver side and passenger
side sensors.
The heated seat elements and sensors cannot be
repaired. If damaged or faulty, the front seat cushion
trim cover or front seat back trim cover assembly
must be replaced. Refer toFront Seat Cushion
Cover - Quad CaborFront Seat Back Cover -
Quad Cabin the index of this service manual for
the location of the proper front seat trim cover
removal and installation procedures.
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.
Fig. 5 Heated Seat Cushion Trim Cover
1 - TO SEAT BACK COVER
2 - TO SEAT WIRE HARNESS
3 - FOAM PADDING
4 - HEATED SEAT CUSHION TRIM COVER
5 - TO ELEMENT GRIDS
6 - TO ELEMENT GRIDS AND SENSOR
8G - 10 HEATED SEAT SYSTEMBR/BE
DRIVER SEAT HEATER SWITCH (Continued)

DIAGNOSIS & TESTING - HEATED SEAT
ELEMENT AND SENSOR
The heated seat module will self-diagnose shorted
or open heated seat element circuits and the sensor
circuits. Refer toHeated Seat Systemin this sec-
tion for the location of the proper heated seat system
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 heated seat element and sensor and for the
seat back heated seat element are located under the
seat, near the rear edge of the seat cushion frame.
Refer toWiring Diagramsfor the location of com-
plete heated seat system wiring diagrams.
HEATED SEAT ELEMENT
(1) Disconnect and isolate the battery negative
cable. Disconnect the 4-way heated seat wire harness
connector. Check for continuity between the two
heated seat element circuit cavities in the seat cush-
ion trim cover half of the 4-way heated seat wire har-
ness connector. There should be continuity. If OK, go
to Step 2. If not OK, go to Step 3.
(2) Check for continuity between one of the heated
seat element circuit cavities in the seat cushion trim
cover half of the 4-way heated seat wire harness con-
nector and the seat cushion frame. There should be
no continuity. If OK, go to Step 5. If not OK, go to
Step 4.
(3) Disconnect the 2-way heated seat wire harness
connector between the seat cushion trim cover and
the seat back trim cover. Check for continuity
between the heated seat element circuit cavity and
the ground circuit cavity in the seat back trim cover
half of the 2-way heated seat wire harness connector.
There should be continuity. If OK, go to Step 5. If not
OK, replace the faulty seat back trim cover unit.
(4) Check for continuity between the heated seat
element circuit cavity in the seat back trim cover half
of the 2-way heated seat wire harness connector and
the seat back frame. There should be no continuity. If
OK, go to Step 5. If not OK, replace the faulty seat
back trim cover unit.
(5) Test the seat wire harness between the heated
seat module connector and the 4-way heated seat
wire harness connectors for shorted or open circuits.
If OK, replace the faulty seat cushion trim cover
unit. If not OK, repair the shorted or open seat wire
harness as required.
HEATED SEAT SENSOR
(1) Disconnect and isolate the battery negative
cable. Disconnect the 4-way heated seat wire harness
connector. Using an ohmmeter, check the resistance
between the heated seat sensor input circuit cavity
and the heated seat sensor feed circuit cavity in theseat cushion cover half of the 4-way heated seat wire
harness connector. The heated seat sensor resistance
should be between 1 kilohm and 200 kilohms. If OK,
go to Step 2. If not OK, replace the faulty seat cush-
ion trim cover unit.
(2) 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 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
diagnosis and testing procedures. If not OK, repair
the shorted or open heated seat wire harness as
required.
HEATED SEAT RELAY
DESCRIPTION
The heated seat relay is an electromechanical
device that switches battery current to the heated
seat module when the relay control coil is energized.
The heated seat relay is located in the Junction
Block (JB), on the left end of the instrument panel in
the passenger compartment (Fig. 6). The heated seat
relay is a International Standards Organization
(ISO) micro-relay. Relays conforming to the ISO spec-
Fig. 6 Heated Seat Relay
1 - JUNCTION BLOCK
2 - HEATED SEAT RELAY
3 - INSTRUMENT PANEL
4 - COMBINATION FLASHER
BR/BEHEATED SEAT SYSTEM 8G - 11
HEATED SEAT ELEMENT (Continued)