2002 DODGE RAM Service Repair Manual

wiring turn signal bulb radiator cap check transmission fluid tire pressure reset wheel size

Page 385 of 2255

DODGE RAM 2002 Service Repair 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)

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)

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DODGE RAM 2002 Service Repair Manual 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 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)

Page 387 of 2255

DODGE RAM 2002 Service Repair Manual RIGHT SEAT HEATER INOPERATIVE
(1) If a heated seat heats but one or both indicator
lamps (LEDs) on the heated seat switch fail to illu-
minate, check the driver circuit with the inoperative
LED for a

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)

Page 388 of 2255

DODGE RAM 2002 Service Repair Manual (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 hea

(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)

Page 389 of 2255

Page 390 of 2255

DODGE RAM 2002 Service Repair Manual ENGINE SYSTEMS
TABLE OF CONTENTS
page page
BATTERY SYSTEM......................... 1
CHARGING.............................. 25STARTING............................... 31
BATTERY SYSTEM
TABLE OF CONTENT

ENGINE SYSTEMS
TABLE OF CONTENTS
page page
BATTERY SYSTEM......................... 1
CHARGING.............................. 25STARTING............................... 31
BATTERY SYSTEM
TABLE OF CONTENTS
page page
BATTERY SYSTEM
DESCRIPTION..........................1
OPERATION............................2
DIAGNOSIS AND TESTING - BATTERY
SYSTEM.............................2
CLEANING.............................5
INSPECTION...........................6
SPECIFICATIONS
BATTERY............................6
SPECIAL TOOLS........................7
BATTERY
DESCRIPTION..........................7
DIAGNOSIS AND TESTING - BATTERY.......7
STANDARD PROCEDURE
STANDARD PROCEDURE - BATTERY
CHARGING...........................8
STANDARD PROCEDURE - BUILT-IN
INDICATOR TEST.....................10
STANDARD PROCEDURE - HYDROMETER
TEST...............................11
STANDARD PROCEDURE - OPEN-CIRCUIT
VOLTAGE TEST.......................12
STANDARD PROCEDURE - LOAD TEST....12
STANDARD PROCEDURE - IGNITION-OFF
DRAW TEST.........................13
STANDARD PROCEDURE - USING
MIDTRONICS ELECTRICAL TESTER.......15REMOVAL.............................16
INSTALLATION.........................16
BATTERY HOLDDOWN
DESCRIPTION.........................17
OPERATION...........................17
REMOVAL.............................17
INSTALLATION.........................18
BATTERY CABLE
DESCRIPTION.........................18
OPERATION...........................18
DIAGNOSIS AND TESTING - BATTERY
CABLES............................19
REMOVAL
POSITIVE CABLE REMOVAL - GASOLINE
ENGINE.............................21
NEGATIVE CABLE REMOVAL - GASOLINE
ENGINE.............................22
INSTALLATION
POSITIVE CABLE INSTALLATION -
GASOLINE ENGINE....................22
NEGATIVE CABLE INSTALLATION -
GASOLINE ENGINE....................22
BATTERY TRAY
DESCRIPTION.........................23
OPERATION...........................23
REMOVAL.............................23
INSTALLATION.........................24
BATTERY SYSTEM
DESCRIPTION
A single 12-volt battery system is standard factory-
installed equipment on gasoline engine equipped
models. Models equipped with a diesel engine utilize
two 12-volt batteries connected in parallel. All of thecomponents of the battery system are located within
the engine compartment of the vehicle. The service
information for the battery system in this vehicle
covers the following related components, which are
covered in further detail elsewhere in this service
manual:
BR/BEENGINE SYSTEMS 8F - 1

Page 391 of 2255

DODGE RAM 2002 Service Repair Manual ²Battery- The storage battery provides a reli-
able means of storing a renewable source of electrical
energy within the vehicle.
²Battery Cable- The battery cables connect the
battery terminal posts

²Battery- The storage battery provides a reli-
able means of storing a renewable source of electrical
energy within the vehicle.
²Battery Cable- The battery cables connect the
battery terminal posts to the vehicle electrical sys-
tem.
²Battery Holddown- The battery holddown
hardware secures the battery in the battery tray in
the engine compartment.
²Battery Tray- The battery tray provides a
secure mounting location in the vehicle for the bat-
tery and an anchor point for the battery holddown
hardware.
For battery system maintenance schedules and
jump starting procedures, see the owner's manual in
the vehicle glove box. Optionally, refer to Lubrication
and Maintenance for the recommended battery main-
tenance schedules and for the proper battery jump
starting procedures. While battery charging can be
considered a maintenance procedure, the battery
charging procedures and related information are
located in the standard procedures section of this ser-
vice manual. This was done because the battery must
be fully-charged before any battery system diagnosis
or testing procedures can be performed. Refer to
Standard procedures for the proper battery charging
procedures.
OPERATION
The battery system is designed to provide a safe,
efficient, reliable and mobile means of delivering and
storing electrical energy. This electrical energy is
required to operate the engine starting system, as
well as to operate many of the other vehicle acces-
sory systems for limited durations while the engine
and/or the charging system are not operating. The
battery system is also designed to provide a reserve
of electrical energy to supplement the charging sys-
tem for short durations while the engine is running
and the electrical current demands of the vehicle
exceed the output of the charging system. In addition
to delivering, and storing electrical energy for the
vehicle, the battery system serves as a capacitor and
voltage stabilizer for the vehicle electrical system. It
absorbs most abnormal or transient voltages caused
by the switching of any of the electrical components
or circuits in the vehicle.
DIAGNOSIS AND TESTING - BATTERY SYSTEM
The battery, starting, and charging systems in the
vehicle operate with one another and must be tested
as a complete system. In order for the engine to start
and the battery to maintain its charge properly, all of
the components that are used in these systems must
perform within specifications. It is important that
the battery, starting, and charging systems be thor-
oughly tested and inspected any time a battery needs
to be charged or replaced. The cause of abnormal bat-
tery discharge, overcharging or early battery failure
must be diagnosed and corrected before a battery is
replaced and before a vehicle is returned to service.
The service information for these systems has been
separated within this service manual to make it eas-
ier to locate the specific information you are seeking.
However, when attempting to diagnose any of these
systems, it is important that you keep their interde-
pendency in mind.
The diagnostic procedures used for the battery,
starting, and charging systems include the most
basic conventional diagnostic methods, to the more
sophisticated On-Board Diagnostics (OBD) built into
the Powertrain Control Module (PCM). Use of an
induction-type milliampere ammeter, a volt/ohmme-
ter, a battery charger, a carbon pile rheostat (load
tester) and a 12-volt test lamp may be required. All
OBD-sensed systems are monitored by the PCM.
Each monitored circuit is assigned a Diagnostic Trou-
ble Code (DTC). The PCM will store a DTC in elec-
tronic memory for any failure it detects. Refer to
Charging System for the proper charging system on-
board diagnostic test procedures.
MIDTRONICS ELECTRICAL SYSTEM TESTER
The Midtronicstautomotive battery and charging
system tester is designed to help the dealership tech-
nicians diagnose the cause of a defective battery or
charging system. Follow the instruction manual sup-
plied with the tester to properly diagnose a vehicle. If
the instruction manual is not available refer to the
standard procedure in this section, which includes
the directions for using the midtronics electrical sys-
tem tester.
8F - 2 BATTERY SYSTEMBR/BE
BATTERY SYSTEM (Continued)

Page 392 of 2255

DODGE RAM 2002 Service Repair Manual BATTERY SYSTEM DIAGNOSIS
CONDITION POSSIBLE CAUSES CORRECTION
THE BATTERY SEEMS
WEAK OR DEAD WHEN
ATTEMPTING TO START
THE ENGINE.1. The electrical system
ignition-off draw is excessive.1. Refer to the

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