2002 DODGE RAM Wiring diagram

with dual battery system, this procedure must
be performed on driver side battery only.
(6) If equipped with dual battery system (certain
diesel equipped models), connect positive lead of volt-
meter to positive battery cable clamp on battery
located on left side of vehicle. Connect negative lead
of voltmeter to positive battery terminal post on bat-
tery located on right side of vehicle. Rotate and holdignition switch in Start position. Observe voltmeter.
If reading is above 0.2 volt, clean and tighten battery
cables at both batteries. Repeat test. If reading is
still above 0.2 volt, replace faulty positive battery
cable.
If resistance tests detect no feed circuit problems,
refer toStarter Motorin the Diagnosis and Testing.
CONTROL CIRCUIT TESTING
The starter control circuit components should be
tested in the order in which they are listed, as fol-
lows:
²Starter Relay- Refer toStarter RelayDiag-
nosis and Testing.
²Starter Solenoid- Refer toStarter Motor
Diagnosis and Testing.
²Ignition Switch- Refer toIgnition Switch
and Key Lock Cylinder
²Clutch Pedal Position Switch- If equipped
with manual transmission, refer toClutch Pedal
Position Switchin 6, Clutch.
²Park/Neutral Position Switch- If equipped
with automatic transmission, refer toPark/Neutral
Position Switchin 21, Transmission.
²Wire harnesses and connections- Refer to 8,
Wiring Diagrams.
SPECIFICATIONS
STARTING SYSTEM
Starter Motor and Solenoid
Manufacturer Nippon Denso Nippon Denso Nippon Denso
Part Number 56027702AB 56027703AB 4741012
Engine Application 5.9L (Gasoline) 8.0L (Gasoline) 5.9L (Diesel)
Power Rating1.4 Kilowatt
1.9 Horsepower1.4 Kilowatt
1.9 Horsepower2.7 Kilowatt
3.6 Horsepower
Voltage 12 Volts 12 Volts 12 Volts
Pinion Teeth 10 11 13
Number of Fields 4 4 4
Number of Poles 4 4 4
Number of Brushes 4 4 4
Drive Type Reduction Gear Train Reduction Gear Train Conventional Gear Train
Free Running Test Voltage 11 Volts 11 Volts 11 Volts
Free Running Test Amperage
Draw73 Amperes 73 Amperes 200 Amperes
Free Running Test Minimum
Speed3601 rpm 3601 rpm 3000 rpm
Fig. 6 Test Starter Ground - Typical
1 - STARTER MOTOR
2 - BATTERY
3 - VOLTMETER
8F - 36 STARTINGBR/BE
STARTING (Continued)

STARTER MOTOR RELAY
DESCRIPTION
The starter relay is an electromechanical device
that switches battery current to the pull-in coil of the
starter solenoid when ignition switch is turned to
Start position. The starter relay is located in the
Power Distribution Center (PDC) in the engine com-
partment. See PDC cover for relay identification and
location.
The starter relay is a International Standards
Organization (ISO) relay. Relays conforming to ISO
specifications have common physical dimensions, cur-
rent capacities, terminal patterns, and terminal func-
tions.
The starter relay cannot be repaired or adjusted
and, if faulty or damaged, it must be replaced.
OPERATION
The ISO relay consists of an electromagnetic coil, a
resistor or diode, and three (two fixed and one mov-
able) electrical contacts. The movable (common feed)
relay contact is held against one of the fixed contacts
(normally closed) by spring pressure. When electro-
magnetic coil is energized, it draws the movable con-
tact away from normally closed fixed contact, and
holds it against the other (normally open) fixed con-
tact.
When electromagnetic coil is de-energized, spring
pressure returns movable contact to normally closed
position. The resistor or diode is connected in parallel
with electromagnetic coil within relay, and helps to
dissipate voltage spikes produced when coil is de-en-
ergized.
DIAGNOSIS AND TESTING - STARTER RELAY
The starter relay (Fig. 13) is located in Power Dis-
tribution Center (PDC). Refer to PDC cover for relay
identification and location. For complete starter relay
wiring circuit diagrams, refer to 8, Wiring Diagrams.
(1) Remove starter relay from PDC.
(2) A relay in de-energized position should have
continuity between terminals 87A and 30, and no
continuity between terminals 87 and 30. If OK, go to
Step 3. If not OK, replace faulty relay.
(3) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 75   5 ohms. If OK, go to Step
4. If not OK, replace faulty relay.
(4) Connect 12V 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, perform Relay Circuit Test that fol-
lows. If not OK, replace 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 open cir-
cuit to fuse in PDC 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.
(3) The relay normally open terminal (87) is con-
nected to common feed terminal (30) in the energized
position. This terminal supplies battery voltage to
starter solenoid field coils. There should be continu-
ity between cavity for relay terminal 87 and starter
solenoid terminal at all times. If OK, go to Step 4. If
not OK, repair open circuit to starter solenoid as
required.
(4) The coil battery terminal (86) is connected to
electromagnet in relay. It is energized when ignition
switch is held in Start position. On vehicles with
manual transmission, clutch pedal must be fully
depressed for this test. Check for battery voltage at
cavity for relay terminal 86 with ignition switch in
Start position, and no voltage when ignition switch is
released to On position. If OK, go to Step 5. If not
OK with automatic transmission, check for open or
short circuit to ignition switch and repair, if required.
If circuit to ignition switch is OK, refer toIgnition
Switch and Key Lock Cylinder. If not OK with a
manual transmission, check circuit between relay
and clutch pedal position switch for open or a short.
Fig. 13 Starter Relay
TERMINAL LEGEND
NUMBER IDENTIFICATION
30 COMMON FEED
85 COIL GROUND
86 COIL BATTERY
87 NORMALLY OPEN
87A NORMALLY CLOSED
BR/BESTARTING 8F - 41

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)

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)

If the heated seat system failure is identified by
flashing heated seat switch indicator lamps, go to the
appropriate diagnosis and testing procedure in this
section and confirm the condition, using the step by
step procedure. If the monitored failure is confirmed,
replace the component. If the monitored failure is not
confirmed, replace the heated seat module with a
known good unit and retest the system.
HEATED SEAT SYSTEM TESTING
Refer toWiring Diagramsfor the location of com-
plete heated seat system wiring diagrams. Before
testing the individual components in the heated seat
system, perform the following preliminary checks:
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
CABLE, THEN WAIT TWO MINUTES FOR THE AIR-
BAG 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.
²If the heated seat switch back lighting and the
cluster illumination lamps do not illuminate with the
headlamps or park lamps turned On, refer to the
Instrument Clustersection of the service manual
for the location of cluster illumination lamps diagno-
sis and testing procedures. If the heated seat switch
back lighting does not illuminate, but the cluster illu-
mination lamps do illuminate with the headlamps or
park lamps turned On, refer toDiagnosis and Test-
ing the Heated Seat Switchin this section for the
location of the heated seat switch diagnosis and test-
ing procedures.
²If a single indicator lamp for one heated seat
switch does not operate and the heated seat elements
do heat, refer toDiagnosis and Testing the
Heated Seat Switchin this section for heated seat
switch diagnosis and testing procedures.
²If both indicator lamps for a heated seat switch
operate, but the heated seat elements do not heat,
refer toDiagnosis and Testing the Heated Seat
Modulein Electronic Control Modules for heated
seat module diagnosis 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 toDiagnosis
and Testing the Heated Seat Relayin the Power
Distribution section of the service manual for heated
seat relay diagnosis and testing procedures.²If the an indicator lamp on either heated seat
switch remains illuminated after the heated seat has
been turned Off, refer toDiagnosis and Testing
the Heated Seat Modulein Electronic Control
Modules for heated seat module diagnosis and test-
ing procedures. Also refer to the Body Diagnostic
Manual for additional diagnosis and testing proce-
dures.DRIVER SEAT HEATER
SWITCH
DESCRIPTION
The heated seat switches are both mounted in a
heated seat switch bezel (Fig. 2), which replaces the
standard equipment cubby 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 identical in appearance and construc-
tion, except for the location of a keyway in the single
connector receptacle on the back of each switch. The
instrument panel wire harness connectors for the
heated seat switches are keyed to match the connec-
Fig. 2 Heated Seat Switches
1 - Driver Switch
2 - Passenger Switch
3 - Indicator Lamps
4 - Heated Seat Switch Bezel
BR/BEHEATED SEAT SYSTEM 8G - 7
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)

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)