Electronic Control Modules DODGE RAM 2002 Service Owner's Manual

To avoid possible voltage spike damage to the
PCM, ignition key must be off, and negative battery
cable must be disconnected before unplugging PCM
connectors.
(1) Disconnect negative battery cable(s) at bat-
tery(s).
(2) Remove cover over electrical connectors. Cover
snaps onto PCM.
(3) Carefully unplug the three 32±way connectors
from PCM.
(4) Remove three PCM mounting bolts and remove
PCM from vehicle.
INSTALLATION
USE THE DRB SCAN TOOL TO REPROGRAM
THE NEW POWERTRAIN CONTROL MODULE
(PCM) WITH THE VEHICLES ORIGINAL IDEN-
TIFICATION NUMBER (VIN) AND THE VEHI-
CLES ORIGINAL MILEAGE. IF THIS STEP IS
NOT DONE, A DIAGNOSTIC TROUBLE CODE
(DTC) MAY BE SET.
(1) Install PCM and mounting bolts to vehicle.
(2) Tighten bolts to 4 N´m (35 in. lbs.).
(3) Check pin connectors in the PCM and the three
32±way connectors for corrosion or damage. Repair
as necessary.
(4) Install three 32±way connectors.
(5) Install cover over electrical connectors. Cover
snaps onto PCM.
(6) Install battery cable(s).
(7) Use the DRB scan tool to reprogram new PCM
with vehicles original Identification Number (VIN)
and original vehicle mileage. If this step is not done,
a Diagnostic Trouble Code (DTC) may be set.
HEATED SEAT MODULE
DESCRIPTION
The heated seat module is also known as the Seat
Heat Interface Module. The heated seat module (Fig.
19) is located under the front seat center cushion,
where it is secured to a mounting bracket that also
serves as the support for the slide-out rear seat cup
holder unit. The mounting tabs that are molded into
the plastic housing of the heated seat module are
inserted through holes in the mounting bracket and
then secured by push on retainers. The heated seat
module has a single connector receptacle that allows
the module to be connected to all of the required
inputs and outputs through the seat wire harness.
The heated seat module is an electronic micropro-
cessor controlled device designed and programmed to
use inputs from the heated seat relay, the two heated
seat switches and the two heated seat sensors to
operate and control the heated seat elements in both
front seats and the two heated seat indicator lamp
Light-Emitting Diodes (LEDs) in each heated seat
switch. The heated seat module is also programmed
to perform self-diagnosis of certain heated seat sys-
tem functions and provide feedback of that diagnosis
through the heated seat switch indicator lamps.
The heated seat module cannot be repaired. If the
heated seat module is damaged or faulty, the entire
module must be replaced.
OPERATION
The heated seat module operates on fused battery
current received from the heated seat relay. The
module is grounded at all times through a ground
screw located below the left rear speaker in the cab
Fig. 18 PCM Location and Mounting
1 - PCM MOUNTING BOLTS (3)
2 - POWERTRAIN CONTROL MODULE (PCM)
3 - (3) 32±WAY CONNECTORS
Fig. 19 Heated Seat Module
1 - MOUNTING TABS
2 - HEATED SEAT MODULE
3 - CONNECTOR RECEPTACLE
8E - 20 ELECTRONIC CONTROL MODULESBR/BE
POWERTRAIN CONTROL MODULE (Continued)

of the vehicle. Inputs to the module include a resistor
multiplexed heated seat switch request circuit for
each of the two heated seat switches and the heated
seat sensor inputs from the seat cushions of each
front seat. In response to those inputs the heated
seat module controls battery current feeds to the
heated seat elements and sensors, and controls the
ground for the heated seat switch indicator lamps.
NOTE: The vehicle's engine must be running in
order for the heated seat system to function. This
eliminates the possibility of draining the vehicles
battery voltage while operating the heated seat sys-
tem.
When a heated seat switch (Driver or Passenger) is
depressed a signal is received by the heated seat
module, the module energizes the proper indicator
LED (Low or High) in the switch by grounding the
indicator lamp circuit to indicate that the heated seat
system is operating. At the same time, the heated
seat module energizes the selected heated seat sensor
circuit and the sensor provides the module with an
input indicating the surface temperature of the
selected seat cushion.
The Low heat set point is about 36É C (96.8É F),
and the High heat set point is about 42É C (107.6É F).
If the seat cushion surface temperature input is
below the temperature set point for the selected tem-
perature setting, the heated seat module energizes
an N-channel Field Effect Transistor (N-FET) within
the module which energizes the heated seat elements
in the selected seat cushion and back. When the sen-
sor input to the module indicates the correct temper-
ature set point has been achieved, the module
de-energizes the N-FET which de-energizes the
heated seat elements. The heated seat module will
continue to cycle the N-FET as needed to maintain
the selected temperature set point.
If the heated seat module detects a heated seat
sensor value input that is out of range or a shorted
or open heated seat element circuit, it will notify the
vehicle operator or the repair technician of this con-
dition by flashing the High and/or Low indicator
lamps in the affected heated seat switch. Refer to
Diagnosis and Testing Heated Seat Systemin
Heated Systems for flashing LED diagnosis and test-
ing procedures. Refer toDiagnosis and Testing
Heated Seat Modulein this section for heated seat
module diagnosis and testing procedures. Also refer
to the Body Diagnostic Manual for additional diagno-
sis and testing procedures.DIAGNOSIS AND TESTING - HEATED SEAT
MODULE
If a heated seat fails to heat and one or both of the
indicator lamps on a heated seat switch flash, refer
toHeated Seat System Diagnosis and Testingin
Heated Systems for flashing LED failure identifica-
tion. Refer toWiring Diagramsin for complete
heated seat system wiring diagrams.
(1) Remove the heated seat module from its
mounting location (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/MEMORY HEATED
SEAT/MIRROR MODULE - REMOVAL).
NOTE: IN ORDER TO PERFORM THE FOLLOWING
TESTS IT WILL BE NECESSARY TO REMOVE THE
HEATED SEAT RELAY AND INSTALL A JUMPER
WIRE IN TERMINALS 87 AND 30, BYPASSING THE
HEATED SEAT RELAY.
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. 20 Heated Seat Module Electrical Connector
BR/BEELECTRONIC CONTROL MODULES 8E - 21
HEATED SEAT MODULE (Continued)

RIGHT SEAT HEATER INOPERATIVE
(1) If a heated seat heats but one or both indicator
lamps (LED's) on the heated seat switch fail to illu-
minate, check the driver circuit with the inoperative
LED for a short to ground. If OK, replace the heated
seat switch. If NOT OK repair the short to ground as
required and than replace the heated seat switch.
NOTE: IF THE RIGHT SEAT CUSHION IS ALREADY
WARM THE FOLLOWING STEP WILL NOT PROVE
CONCLUSIVE.
(2) Back-probe the heated seat module wire har-
ness connector (Fig. 20) , do not disconnect. Check
cavity #3 for battery voltage when the right heated
seat switch is turned ªONº, voltage should be
present, If OK go to Step 3 If NOT OK, test the right
heated seat switch (Refer to 8 - ELECTRICAL/
HEATED SEATS/PASSENGER HEATED SEAT
SWITCH - DIAGNOSIS AND TESTING). If the
switch tests OK, check for continuity between the
switch and control module on the MUX circuit, If OK
replace the heated seat control module. If NOT OK,
repair the open or shorted MUX circuit as required.
NOTE: BE CERTAIN THE BATTERY IS FULLY
CHARGED BEFORE TESTING. FAILURE TO DO SO
CAN RESULT IN INCORRECT READINGS.
(3) Back-probe the heated seat module wire har-
ness connector (Fig. 20) , do not disconnect. Check
cavity #10 for battery voltage, while observing the
voltmeter depress the right heated seat switchlow
setting twice, voltage should toggle between
approx.12v and 8v, If OK go to Step 4. If NOT OK
check for continuity between the switch and control
module on the low heat driver circuit, If OK replace
the heated seat control module.
(4) Back-probe the heated seat module wire har-
ness connector (Fig. 20) , do not disconnect. Check
cavity #11 for battery voltage, while observing the
voltmeter depress the right heated seat switchhigh
setting twice, voltage should toggle between
approx.12v and 8v, If OK go to Step 5. If NOT OK
check for continuity between the switch and control
module on the high heat driver circuit, If OK replace
the heated seat control module.
(5) Back-probe the heated seat module wire har-
ness connector (Fig. 20) , do not disconnect. Check
cavity #2 for approx. 5v, voltage should be present, If
OK go to Step 6. If NOT OK replace the heated seat
control module.
(6) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity #7 for
a range in voltage from 1.72v (warm seat) ± 3.0v
(cold seat). It should be within this range, If OK
replace the heated seat module. If NOT OK test theHeated Seat Sensor. If NOT OK, replace the right
heated seat element and sensor assembly. If the
heated seat sensor tests OK, check for continuity
between the right heated seat cushion connector and
control module connector on the 5v supply circuit, If
NOT OK, repair the open or shorted 5v supply circuit
as required. If OK check for continuity between the
right heated seat cushion connector and control mod-
ule connector on the temperature sensor input cir-
cuit. If NOT OK, repair the open or shorted
temperature sensor input circuit as required. If OK
replace the heated seat control module.
LEFT SEAT HEATER INOPERATIVE
(1) If a heated seat heats but one or both indicator
lamps (LED's) on the heated seat switch fail to illu-
minate, check the driver circuit with the inoperative
LED for a short to ground. If OK, replace the heated
seat switch. If NOT OK repair the short to ground as
required and than replace the heated seat switch.
NOTE: IF THE LEFT SEAT CUSHION IS ALREADY
WARM THE FOLLOWING STEP WILL NOT PROVE
CONCLUSIVE.
(2) Back-probe the heated seat module wire har-
ness connector (Fig. 20) , do not disconnect. Check
cavity #5 for battery voltage when the left heated
seat switch is turned ªONº, voltage should be
present, If OK go to Step 3 If NOT OK, test the left
heated seat switch (Refer to 8 - ELECTRICAL/
HEATED SEATS/DRIVER HEATED SEAT SWITCH
- DIAGNOSIS AND TESTING). If the switch tests
OK, check for continuity between the switch and con-
trol module on the MUX circuit, If OK replace the
heated seat control module. If NOT OK, repair the
open or shorted MUX circuit as required.
(3) Back-probe the heated seat module wire har-
ness connector (Fig. 20) , do not disconnect. Check
cavity #12 for battery voltage, while observing the
voltmeter depress the left heated seat switchlow
setting twice, voltage should toggle between
approx.12v and 8v, If OK go to Step 4. If NOT OK
check for continuity between the switch and control
module on the low heat driver circuit, If OK replace
the heated seat control module.
(4) Back-probe the heated seat module wire har-
ness connector (Fig. 20) , do not disconnect. Check
cavity #14 for battery voltage, while observing the
voltmeter depress the left heated seat switchhigh
setting twice, voltage should toggle between
approx.12v and 8v, If OK go to Step 5. If NOT OK
check for continuity between the switch and control
module on the high heat driver circuit, If OK replace
the heated seat control module.
8E - 22 ELECTRONIC CONTROL MODULESBR/BE
HEATED SEAT MODULE (Continued)

(5) Back-probe the heated seat module wire har-
ness connector (Fig. 20) , do not disconnect. Check
cavity #2 for approx. 5v, 5 voltage should be present,
If OK go to Step 6. If NOT OK replace the heated
seat control module.
(6) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity #8 for
a range in voltage from 1.72v (warm seat) ± 3.0v
(cold seat). It should be within this range, If OK
replace the heated seat control module. If NOT OK,
test the Heated Seat Sensor. If NOT OK, replace the
left heated seat element and sensor assembly. If the
heated seat sensor tests OK, check for continuity
between the left heated seat cushion connector and
control module connector on the 5v supply circuit, If
NOT OK, repair the open or shorted 5v supply circuit
as required. If OK check for continuity between the
left heated seat cushion connector and control mod-
ule connector on the temperature sensor input cir-
cuit. If NOT OK, repair the open or shorted
temperature sensor input circuit as required. If OK
replace the heated seat control module.
BOTH SEATS INOPERATIVE
If both seats (driver and passenger) fail to heat
and the indicator lamps on the heated seat switches
for both seats fail to operate, test the heated seat
relay and/or fuses. Refer toRelay Diagnosis and
Testingin the Power Distribution section for heated
seat relay diagnosis and testing procedures. If the
heated seat relay checks OK, go to Step 1.
(1) Back-probe the heated seat module wire har-
ness connector (Fig. 20) , do not disconnect. Check for
continuity between the ground circuit cavity #13 of
the heated seat module connector and a good ground.
If OK go to Step 2. If NOT OK, repair the open or
shorted ground circuit as required.
(2) Back-probe the heated seat module wire har-
ness connector (Fig. 20) , do not disconnect. Check
cavity #4 and #6 for battery voltage, voltage should
be present, If OK go to Step 3. If NOT OK repair the
open or shorted fused B(+) circuit as required.
(3) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity #2 for
approx. 5v, voltage should be present, replace the
heated seat control module with a known good mod-
ule and verify system operation.
REMOVAL
(1) Working under the center front seat console,
cut the tiestrap and remove the two push-on retain-
ers that secure the mounting tabs of the heated seat
module to the of the mounting bracket.
(2) Position the driver seat to the full forward and
inclined position and working under the center of the
front seat, from behind the seat, disconnect the seat
wire harness connector from the connector receptacle
on the back of the heated seat module (Fig. 21).
(3) Remove the heated seat module from under the
front seat.
INSTALLATION
(1) Working under the front seat connect the seat
wire harness connector to the connector receptacle on
the back of the heated seat module.
(2) Position the driver seat in the full rearward
and reclined position, and working under the front of
the seat, install the two push-on retainers onto the
heated seat module mounting tabs to secure the mod-
ule to the top of the mounting bracket or install
tiestrap.
Fig. 21 Heated Seat Module Remove/Install
1 - MOUNTING BRACKET
2 - HEATED SEAT MODULE
3 - MOUNTING TABS
4 - PUSH-ON RETAINERS
BR/BEELECTRONIC CONTROL MODULES 8E - 23
HEATED SEAT MODULE (Continued)

(3) Rotate the load control knob (carbon pile rheo-
stat) to apply a 300 ampere load to the battery for
fifteen seconds, then return the control knob to the
Off position (Fig. 12). This will remove the surface
charge from the battery.
(4) Allow the battery to stabilize to open-circuit
voltage. It may take up to five minutes for the bat-
tery voltage to stabilize.
(5) Rotate the load control knob to maintain a load
equal to 50% of the CCA rating of the battery (Fig.
13). After fifteen seconds, record the loaded voltage
reading, then return the load control knob to the Off
position.
(6) The voltage drop will vary with the battery
temperature at the time of the load test. The battery
temperature can be estimated by using the ambient
temperature during the past several hours. If the
battery has been charged, boosted, or loaded a few
minutes prior to the test, the battery will be some-
what warmer. See the Load Test Temperature Table
for the proper loaded voltage reading.
LOAD TEST TEMPERATURE TABLE
Minimum VoltageTemperature
ÉF ÉC
9.6 volts 70É and above 21É and above
9.5 volts 60É 16É
9.4 volts 50É 10É
9.3 volts 40É 4É
9.1 volts 30É -1É
8.9 volts 20É -7É
8.7 volts 10É -12É
8.5 volts 0É -18É
(7) If the voltmeter reading falls below 9.6 volts, at
a minimum battery temperature of 21É C (70É F), the
battery is faulty and must be replaced.
STANDARD PROCEDURE - IGNITION-OFF
DRAW TEST
The term Ignition-Off Draw (IOD) identifies a nor-
mal condition where power is being drained from the
battery with the ignition switch in the Off position. A
normal vehicle electrical system will draw from five
to thirty-five milliamperes (0.005 to 0.035 ampere)
with the ignition switch in the Off position, and all
non-ignition controlled circuits in proper working
order. Up to thirty-five milliamperes are needed to
enable the memory functions for the Powertrain Con-
trol Module (PCM), digital clock, electronically tuned
radio, and other modules which may vary with the
vehicle equipment.
A vehicle that has not been operated for approxi-
mately twenty days, may discharge the battery to an
inadequate level. When a vehicle will not be used for
twenty days or more (stored), remove the IOD fuse
from the Junction Block. This will reduce battery dis-
charging.
Fig. 11 Volt-Ammeter-Load
1 - INDUCTION AMMETER CLAMP
2 - NEGATIVE CLAMP
3 - POSITIVE CLAMP
Fig. 12 Remove Surface Charge from Battery
Fig. 13 Load 50% CCA Rating - Note Voltage -
Typical
BR/BEBATTERY SYSTEM 8F - 13
BATTERY (Continued)

Excessive IOD can be caused by:
²Electrical items left on.
²Faulty or improperly adjusted switches.
²Faulty or shorted electronic modules and compo-
nents.
²An internally shorted generator.
²Intermittent shorts in the wiring.
If the IOD is over thirty-five milliamperes, the
problem must be found and corrected before replac-
ing a battery. In most cases, the battery can becharged and returned to service after the excessive
IOD condition has been corrected.
(1) Verify that all electrical accessories are off.
Turn off all lamps, remove the ignition key, and close
all doors. If the vehicle is equipped with an illumi-
nated entry system or an electronically tuned radio,
allow the electronic timer function of these systems
to automatically shut off (time out). This may take
up to three minutes. See the Electronic Module Igni-
tion-Off Draw Table for more information.
ELECTRONIC MODULE IGNITION-OFF DRAW (IOD) TABLE
ModuleTime Out?
(If Yes, Interval And Wake-Up Input)IOD IOD After Time Out
Radio No 1 to 3 milliamperes N/A
Audio Power
AmplifierNo up to 1 milliampere N/A
Central Timer
Module (CTM)No4.75 milliamperes
(max.)N/A
Powertrain Control
Module (PCM)No 0.95 milliampere N/A
ElectroMechanical
Instrument Cluster
(EMIC)No 0.44 milliampere N/A
Combination Flasher No 0.08 milliampere N/A
(2) Determine that the underhood lamp is operat-
ing properly, then disconnect the lamp wire harness
connector or remove the lamp bulb.
(3) Disconnect the battery negative cable.
(4) Set an electronic digital multi-meter to its
highest amperage scale. Connect the multi-meter
between the disconnected battery negative cable ter-
minal clamp and the battery negative terminal post.
Make sure that the doors remain closed so that the
illuminated entry system is not activated. The multi-
meter amperage reading may remain high for up to
three minutes, or may not give any reading at all
while set in the highest amperage scale, depending
upon the electrical equipment in the vehicle. The
multi-meter leads must be securely clamped to the
battery negative cable terminal clamp and the bat-
tery negative terminal post. If continuity between the
battery negative terminal post and the negative cable
terminal clamp is lost during any part of the IOD
test, the electronic timer function will be activated
and all of the tests will have to be repeated.
(5) After about three minutes, the high-amperage
IOD reading on the multi-meter should become very
low or nonexistent, depending upon the electrical
equipment in the vehicle. If the amperage reading
remains high, remove and replace each fuse or circuit
breaker in the Power Distribution Center (PDC) andthen in the Junction Block (JB), one at a time until
the amperage reading becomes very low, or nonexist-
ent. Refer to the appropriate wiring information in
this service manual for complete PDC and JB fuse,
circuit breaker, and circuit identification. This will
isolate each circuit and identify the circuit that is the
source of the high-amperage IOD. If the amperage
reading remains high after removing and replacing
each fuse and circuit breaker, disconnect the wire
harness from the generator. If the amperage reading
now becomes very low or nonexistent, refer to Charg-
ing System for the proper charging system diagnosis
and testing procedures. After the high-amperage IOD
has been corrected, switch the multi-meter to pro-
gressively lower amperage scales and, if necessary,
repeat the fuse and circuit breaker remove-and-re-
place process to identify and correct all sources of
excessive IOD. It is now safe to select the lowest mil-
liampere scale of the multi-meter to check the low-
amperage IOD.
CAUTION: Do not open any doors, or turn on any
electrical accessories with the lowest milliampere
scale selected, or the multi-meter may be damaged.
(6) Observe the multi-meter reading. The low-am-
perage IOD should not exceed thirty-five milliam-
peres (0.035 ampere). If the current draw exceeds
8F - 14 BATTERY SYSTEMBR/BE
BATTERY (Continued)

²a faulty or improperly adjusted switch that
allows a lamp to stay on. Refer to Ignition-Off Draw
Test in 8, Battery for more information.
INSPECTION
The Powertrain Control Module (PCM) monitors
critical input and output circuits of the charging sys-
tem, making sure they are operational. A Diagnostic
Trouble Code (DTC) is assigned to each input and
output circuit monitored by the On-Board Diagnostic
(OBD) system. Some charging system circuits are
checked continuously, and some are checked only
under certain conditions.
Refer to Diagnostic Trouble Codes in; Powertrain
Control Module; Electronic Control Modules for more
DTC information. This will include a complete list of
DTC's including DTC's for the charging system.
To perform a complete test of the charging system,
refer to the appropriate Powertrain Diagnostic Proce-
dures service manual and the DRBtscan tool. Per-
form the following inspections before attaching the
scan tool.
(1) Inspect the battery condition. Refer to 8, Bat-
tery for procedures.(2) Inspect condition of battery cable terminals,
battery posts, connections at engine block, starter
solenoid and relay. They should be clean and tight.
Repair as required.
(3) Inspect all fuses in both the fuseblock and
Power Distribution Center (PDC) for tightness in
receptacles. They should be properly installed and
tight. Repair or replace as required.
(4) Inspect generator mounting bolts for tightness.
Replace or tighten bolts if required. Refer to the Gen-
erator Removal/Installation section of this group for
torque specifications.
(5) Inspect generator drive belt condition and ten-
sion. Tighten or replace belt as required. Refer to
Belt Tension Specifications in 7, Cooling System.
(6) Inspect automatic belt tensioner (if equipped).
Refer to 7, Cooling System for information.
(7) Inspect generator electrical connections at gen-
erator field, battery output, and ground terminal (if
equipped). Also check generator ground wire connec-
tion at engine (if equipped). They should all be clean
and tight. Repair as required.
SPECIFICATIONS
GENERATOR RATINGS
TYPE PART NUMBER RATED SAE AMPS ENGINESMINIMUM TEST
AMPS
DENSO 56028920AB 1365.9L
GAS100
DENSO 56029913AA 1175.9L
GAS90
BOSCH 56028237AB 1175.9L
GAS90
BOSCH 56028238AB 1365.9L
GAS100
DENSO 56027221AD 1365.9L
DIESEL120
BOSCH 56028239AB 1365.9L
DIESEL120
BOSCH 56028560AA 136 8.0L 100
DENSO 560289200AC 136 8.0L 100
8F - 26 CHARGINGBR/BE
CHARGING (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

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)