2002 DODGE RAM Service Repair Manual

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Page 441 of 2255

DODGE RAM 2002 Service Repair Manual (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 av

(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)

Page 442 of 2255

DODGE RAM 2002 Service Repair Manual 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 wi

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)

Page 443 of 2255

DODGE RAM 2002 Service Repair Manual (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 testi

Page 444 of 2255

DODGE RAM 2002 Service Repair Manual (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

(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)

Page 445 of 2255

DODGE RAM 2002 Service Repair Manual (2) Connect the new heating element electrical
connectors (Fig. 12) .
(3) Connect the negative battery cable.
(4) Verify heated seat system operation.
(5) Install the appropriate seat cushion or seat

Page 446 of 2255

DODGE RAM 2002 Service Repair Manual ical dimensions are smaller than those of the conven-
tional ISO relay.
The heated seat relay cannot be repaired or
adjusted and, if faulty or damaged, it must be
replaced.
OPERATION
The ISO relay con

ical dimensions are smaller than those of the conven-
tional ISO relay.
The heated seat relay cannot be repaired or
adjusted and, if faulty or damaged, it must be
replaced.
OPERATION
The ISO relay consists of an electromagnetic coil, a
resistor or diode, and three (two fixed and one mov-
able) electrical contacts. The movable (common feed)
relay contact is held against one of the fixed contacts
(normally closed) by spring pressure. When the elec-
tromagnetic coil is energized, it draws the movable
contact away from the normally closed fixed contact,
and holds it against the other (normally open) fixed
contact. When the electromagnetic coil is de-ener-
gized, spring pressure returns the movable contact to
the normally closed position. The resistor or diode is
connected in parallel with the electromagnetic coil in
the relay, and helps to dissipate voltage spikes that
are produced when the coil is de-energized.
The heated seat relay is controlled by the premium
version of the Central Timer Module (CTM), which
controls the ground feed to the coil ground terminal
of the relay to energize and de-energize the electro-
magnetic coil of the relay. The CTM monitors engine
operation through messages it receives from the Pow-
ertrain Control Module (PCM) over the Chrysler Col-
lision Detection (CCD) data bus network. The CTM is
programmed to energize the relay only when the
engine is running, and to de-energize the relay when
the engine is not running. Refer toCentral Timer
Modulein the index of this service manual for the
location of more information on the premium CTM.
DIAGNOSIS AND TESTING - HEATED SEAT
RELAY
The heated seat relay (Fig. 15) is located in the
Junction Block (JB) on the left end of the instrument
panel in the passenger compartment of the vehicle.
Refer toWiring Diagramsfor the location of com-
plete heated seat system wiring diagrams.
WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS,
DISABLE THE AIRBAG SYSTEM BEFORE ATTEMPT-
ING ANY STEERING WHEEL, STEERING COLUMN, OR
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. DISCONNECT AND ISOLATE THE BATTERY
NEGATIVE (GROUND) CABLE, THEN WAIT TWO MIN-
UTES FOR THE AIRBAG SYSTEM CAPACITOR TO DIS-
CHARGE BEFORE PERFORMING FURTHER
DIAGNOSIS OR SERVICE. THIS IS THE ONLY SURE
WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE TO
TAKE THE PROPER PRECAUTIONS COULD RESULT
IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSI-
BLE PERSONAL INJURY.
RELAY TEST
(1) Remove the heated seat relay from the JB.
Refer toHeated Seat Relayin this section for the
location of the proper heated seat relay removal pro-
cedures.
(2) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to Step 3. If not OK, replace the 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 the faulty relay.
(4) Connect a battery to terminals 85 and 86.
There should now be continuity between terminals
30 and 87, and no continuity between terminals 87A
and 30. If OK, perform the Relay Circuit Test that
follows. If not OK, replace the faulty relay.
RELAY CIRCUIT TEST
(1) The relay common feed terminal cavity (30) is
connected to battery voltage and should be hot at all
times. If OK, go to Step 2. If not OK, repair the open
circuit to the fused B(+) fuse in the Power Distribu-
tion Center (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 the common feed terminal (30) in the ener-
gized position. This terminal supplies battery voltage
to the heated seat module. There should be continu-
ity between the cavity for relay terminal 87 and the
B(+) to heated seat module circuit cavity of the
heated seat module wire harness connector at all
times. If OK, go to Step 4. If not OK, repair the open
Fig. 15 Heated Seat Relay
TERMINAL LEGEND
NUMBER IDENTIFICATION
30 COMMON FEED
85 COIL GROUND
86 COIL BATTERY
87 NORMALLY OPEN
87A NORMALLY CLOSED
BR/BEHEATED SEAT SYSTEM 8G - 15
HEATED SEAT RELAY (Continued)

Page 447 of 2255

DODGE RAM 2002 Service Repair Manual B(+) to heated seat module circuit to the heated seat
module as required.
(4) The coil battery terminal (86) is connected to
the electromagnet in the relay. It is connected to bat-
tery voltage and sh

B(+) to heated seat module circuit to the heated seat
module as required.
(4) The coil battery terminal (86) is connected to
the electromagnet in the relay. It is connected to bat-
tery voltage and should be hot at all times. Check for
battery voltage at the cavity for relay terminal 86. If
OK, go to Step 5. If not OK, repair the open circuit to
the fused B(+) fuse in the PDC as required.
(5) The coil ground terminal (85) is connected to
the electromagnet in the relay. It is grounded by the
premium version of the Central Timer Module (CTM)
in response to an engine speed message received over
the Chrysler Collision Detection (CCD) data bus from
the Powertrain Control Module (PCM) when the
engine is running. Check for continuity between the
cavity for relay terminal 85 and the heated seat relay
control circuit cavity of the CTM wire harness con-
nector. There should be continuity at all times. If OK,
use a DRBIIItscan tool and the proper diagnostic
procedures manual to test the operation of the CTM
and CCD data bus. If not OK, repair the open heated
seat relay control circuit as required.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the fuse access panel by inserting a
finger in the finger recess molded into the panel and
then pulling the panel sharply away from the left
outboard end of the instrument panel.
(3) The heated seat relay is located on the forward
side of the Junction Block (JB), just above the com-
bination flasher (Fig. 16) .
(4) Grasp the heated seat relay firmly and pull it
straight out from the JB.
INSTALLATION
(1) Position the heated seat relay in the proper
receptacle in the JB.
(2) Align the heated seat relay terminals with the
terminal cavities in the JB receptacle.
(3) Push in firmly on the heated seat relay until
the terminals are fully seated in the terminal cavities
in the JB receptacle.
(4) Insert the tabs on the forward edge of the fuse
access panel in the notches on the forward edge of
the instrument panel fuse access panel opening.
(5) Press the rear edge of the fuse access panel in
toward the instrument panel until the panel snaps
back into place.
(6) Reconnect the battery negative cable.
PASSENGER SEAT HEATER
SWITCH
DESCRIPTION
The heated seat switches are both mounted in a
heated seat switch bezel (Fig. 17), 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-
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
Fig. 16 Heated Seat
1 - JUNCTION BLOCK
2 - HEATED SEAT RELAY
3 - INSTRUMENT PANEL
4 - COMBINATION FLASHER
8G - 16 HEATED SEAT SYSTEMBR/BE
HEATED SEAT RELAY (Continued)

Page 448 of 2255

DODGE RAM 2002 Service Repair Manual 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

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 thesame 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
Fig. 17 Heated Seat Switches
1 - Driver Switch
2 - Passenger Switch
3 - Indicator Lamps
4 - Heated Seat Switch Bezel
BR/BEHEATED SEAT SYSTEM 8G - 17
PASSENGER SEAT HEATER SWITCH (Continued)

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