2002 DODGE RAM PCM

The PCM can adapt its programming to meet
changing operating conditions.
The PCM receives input signals from various
switches and sensors. Based on these inputs, the
PCM regulates various engine and vehicle operations
through different system components. These compo-
nents are referred to asPCM Outputs.The sensors
and switches that provide inputs to the PCM are con-
sideredPCM Inputs.
NOTE: PCM Inputs:
²A/C request (if equipped with factory A/C)
²A/C select (if equipped with factory A/C)
²Accelerator Pedal Position Sensor (APPS) output
from ECM
²Auto shutdown (ASD) relay sense
²Battery temperature sensor
²Battery voltage
²Brake switch
²CCD bus (+) circuits
²CCD bus (-) circuits
²Crankshaft Position Sensor (CKP) output from
ECM
²Data link connection for DRB scan tool
²Fuel level sensor
²Generator (battery voltage) output
²Ignition sense
²Output shaft speed sensor
²Overdrive/override switch
²Park/neutral switch (auto. trans. only)
²Power ground
²Sensor return
²Signal ground
²Speed control resume switch
²Speed control set switch
²Speed control on/off switch
²Transmission governor pressure sensor
²Transmission temperature sensor
²Vehicle speed inputs from ABS or RWAL system
NOTE: PCM Outputs:
After inputs are received by the PCM, certain sen-
sors, switches and components are controlled or reg-
ulated by the PCM. These are consideredPCM
Outputs.These outputs are for:
²A/C clutch relay and A/C clutch
²Auto shutdown (ASD) relay
²CCD bus (+/-) circuits for: speedometer, voltme-
ter, fuel gauge, oil pressure gauge/lamp, engine temp.
gauge and speed control warn. lamp
²Data link connection for DRB scan tool
²Five volt sensor supply
²Generator field driver (-)
²Generator field driver (+)
²Generator lamp (if equipped)²Malfunction indicator lamp (Check engine lamp)
²Overdrive warning lamp (if equipped)
²Speed control vacuum solenoid
²Speed control vent solenoid
²Tachometer (if equipped)
²Transmission convertor clutch circuit
²Transmission 3±4 shift solenoid
²Transmission relay
²Transmission temperature lamp (if equipped)
²Transmission variable force solenoid (governor
sol.)
OPERATION - 5 VOLT SUPPLIES
Primary 5±volt supply:
²supplies the required 5 volt power source to the
Crankshaft Position (CKP) sensor.
²supplies the required 5 volt power source to the
Camshaft Position (CMP) sensor.
²supplies a reference voltage for the Manifold
Absolute Pressure (MAP) sensor.
²supplies a reference voltage for the Throttle
Position Sensor (TPS) sensor.
Secondary 5±volt supply:
²supplies the required 5 volt power source to the
oil pressure sensor.
²supplies the required 5 volt power source for the
Vehicle Speed Sensor (VSS) (if equipped).
²supplies the 5 volt power source to the transmis-
sion pressure sensor (if equipped with an RE auto-
matic transmission).
OPERATION - IGNITION CIRCUIT SENSE
The ignition circuit sense input tells the PCM the
ignition switch has energized the ignition circuit.
Battery voltage is also supplied to the PCM
through the ignition switch when the ignition is in
the RUN or START position. This is referred to as
the9ignition sense9circuit and is used to9wake up9
the PCM. Voltage on the ignition input can be as low
as 6 volts and the PCM will still function. Voltage is
supplied to this circuit to power the PCM's 8-volt reg-
ulator and to allow the PCM to perform fuel, ignition
and emissions control functions.
REMOVAL
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.
The PCM is located in the engine compartment
(Fig. 18).
BR/BEELECTRONIC CONTROL MODULES 8E - 19
POWERTRAIN CONTROL MODULE (Continued)

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)

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)

(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)

CHARGING
TABLE OF CONTENTS
page page
CHARGING
DESCRIPTION.........................25
OPERATION...........................25
DIAGNOSIS AND TESTING - CHARGING
SYSTEM............................25
SPECIFICATIONS
GENERATOR RATINGS.................26
SPECIFICATIONS - TORQUE -
GENERATOR/CHARGING SYSTEM........27
BATTERY TEMPERATURE SENSOR
DESCRIPTION.........................27OPERATION...........................27
REMOVAL.............................27
INSTALLATION.........................28
GENERATOR
DESCRIPTION.........................28
OPERATION...........................28
REMOVAL.............................28
INSTALLATION.........................30
VOLTAGE REGULATOR
DESCRIPTION.........................30
OPERATION...........................30
CHARGING
DESCRIPTION
The charging system consists of:
²Generator
²Electronic Voltage Regulator (EVR) circuitry
within the Powertrain Control Module (PCM)
²Ignition switch
²Battery (refer to 8, Battery for information)
²Battery temperature sensor
²Check Gauges Lamp (if equipped)
²Voltmeter (refer to 8, Instrument Panel and
Gauges for information)
²Wiring harness and connections (refer to 8, Wir-
ing Diagrams for information)
OPERATION
The charging system is turned on and off with the
ignition switch. The system is on when the engine is
running and the ASD relay is energized. When the
ASD relay is on, voltage is supplied to the ASD relay
sense circuit at the PCM. This voltage is connected
through the PCM and supplied to one of the genera-
tor field terminals (Gen. Source +) at the back of the
generator.
The amount of direct current produced by the gen-
erator is controlled by the EVR (field control) cir-
cuitry contained within the PCM. This circuitry is
connected in series with the second rotor field termi-
nal and ground.
A battery temperature sensor, located in the bat-
tery tray housing, is used to sense battery tempera-
ture. This temperature data, along with data from
monitored line voltage, is used by the PCM to vary
the battery charging rate. This is done by cycling theground path to control the strength of the rotor mag-
netic field. The PCM then compensates and regulates
generator current output accordingly.
All vehicles are equipped with On-Board Diagnos-
tics (OBD). All OBD-sensed systems, including EVR
(field control) circuitry, 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 certain failures it detects. Refer to
On-Board Diagnostics in 25, Emission Control Sys-
tem for more DTC information and a list of codes.
The Check Gauges Lamp (if equipped) monitors:
charging system voltage,engine coolant tempera-
ture and engine oil pressure. If an extreme condition
is indicated, the lamp will be illuminated. This is
done as reminder to check the three gauges. The sig-
nal to activate the lamp is sent via the CCD bus cir-
cuits. The lamp is located on the instrument panel.
Refer to 8, Instrument Panel and Gauges for addi-
tional information.
DIAGNOSIS AND TESTING - CHARGING
SYSTEM
The following procedures may be used to diagnose
the charging system if:
²the check gauges lamp (if equipped) is illumi-
nated with the engine running
²the voltmeter (if equipped) does not register
properly
²an undercharged or overcharged battery condi-
tion occurs.
Remember that an undercharged battery is often
caused by:
²accessories being left on with the engine not
running
BR/BECHARGING 8F - 25

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)

SPECIFICATIONS - TORQUE - GENERATOR/
CHARGING SYSTEM
DESCRIPTION N´m Ft. Lbs. In. Lbs.
Generator Mounting Bolts
- Gas Engine41 30-
Generator Upper Mounting
Bolt - Diesel Engine54 40 -
Generator Pivot Bolt/Nut -
Diesel Engine54 40 -
Generator Mounting
Bracket-to-Engine Bolt -
Diesel Engine24 18 -
Generator B+ Cable
Eyelet Nut12 9 108
BATTERY TEMPERATURE
SENSOR
DESCRIPTION
The Battery Temperature Sensor (BTS) is attached
to the battery tray located under the battery.
OPERATION
The BTS is used to determine the battery temper-
ature and control battery charging rate. This temper-
ature data, along with data from monitored line
voltage, is used by the PCM to vary the battery
charging rate. System voltage will be higher at colder
temperatures and is gradually reduced at warmer
temperatures.
The PCM sends 5 volts to the sensor and is
grounded through the sensor return line. As temper-
ature increases, resistance in the sensor decreases
and the detection voltage at the PCM increases.
The BTS is also used for OBD II diagnostics. Cer-
tain faults and OBD II monitors are either enabled
or disabled, depending upon BTS input (for example,
disable purge and enable Leak Detection Pump
(LDP) and O2 sensor heater tests). Most OBD II
monitors are disabled below 20ÉF.
REMOVAL
The battery temperature sensor is located under
the vehicle battery (Fig. 1) and is attached (snapped
into) a mounting hole on battery tray. On models
equipped with a diesel engine (dual batteries), only
one sensor is used. The sensor is located under the
battery on drivers side of vehicle.
(1) Remove battery. Refer to 8, Battery for proce-
dures.Fig. 1 Battery Temperature Sensor Location
1 - BATT. TEMP. SENSOR
2 - BATTERY HOLD DOWN STRAP
3 - PIGTAIL HARNESS
4 - U-NUT
5 - U-NUT
6 - ELEC. CONNEC.
BR/BECHARGING 8F - 27
CHARGING (Continued)