Temperature sensor DODGE RAM 2001 Service User Guide

Based on inputs that it receives, the PCM adjusts
ignition coil dwell. The PCM also adjusts the gener-
ator charge rate through control of the generator
field and provides speed control operation.
NOTE: PCM Inputs:
²A/C request (if equipped with factory A/C)
²A/C select (if equipped with factory A/C)
²Auto shutdown (ASD) sense
²Battery temperature
²Battery voltage
²Brake switch
²CCD bus (+) circuits
²CCD bus (-) circuits
²Camshaft position sensor signal
²Crankshaft position sensor
²Data link connection for DRB scan tool
²Engine coolant temperature sensor
²Fuel level
²Generator (battery voltage) output
²Ignition circuit sense (ignition switch in on/off/
crank/run position)
²Intake manifold air temperature sensor
²Leak detection pump (switch) sense (if equipped)
²Manifold absolute pressure (MAP) sensor
²Oil pressure
²Output shaft speed sensor
²Overdrive/override switch
²Oxygen sensors
²Park/neutral switch (auto. trans. only)
²Power ground
²Sensor return
²Signal ground
²Speed control multiplexed single wire input
²Throttle position sensor
²Transmission governor pressure sensor
²Transmission temperature sensor
²Vehicle speed inputs from ABS or RWAL system
NOTE: PCM Outputs:
²A/C clutch relay
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
²EGR valve control solenoid (if equipped)
²EVAP canister purge solenoid
²Five volt sensor supply (primary)
²Five volt sensor supply (secondary)
²Fuel injectors
²Fuel pump relay
²Generator field driver (-)
²Generator field driver (+)
²Generator lamp (if equipped)²Idle air control (IAC) motor
²Ignition coil
²Leak detection pump (if equipped)
²Malfunction indicator lamp (Check engine lamp).
Driven through CCD circuits.
²Overdrive indicator lamp (if equipped)
²Service Reminder Indicator (SRI) Lamp (MAINT
REQ'D lamp). Driven through CCD circuits.
²Speed control vacuum solenoid
²Speed control vent solenoid
²Tachometer (if equipped). Driven through CCD
circuits.
²Transmission convertor clutch circuit
²Transmission 3±4 shift solenoid
²Transmission relay
²Transmission temperature lamp (if equipped)
²Transmission variable force solenoid
OPERATION - DIESEL
Two different control modules are used: The Pow-
ertrain Control Module (PCM), and the Engine Con-
trol Module (ECM). The ECMcontrolsthe fuel
system. The PCMdoes not controlthe fuel system.
The PCM's main function is to control: the vehicle
charging system, speed control system, transmission,
air conditioning system and certain bussed messages.
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)
8E - 18 ELECTRONIC CONTROL MODULESBR/BE
POWERTRAIN CONTROL MODULE (Continued)

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).
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.
Fig. 18 PCM Location and Mounting
1 - PCM MOUNTING BOLTS (3)
2 - POWERTRAIN CONTROL MODULE (PCM)
3 - (3) 32±WAY CONNECTORS
BR/BEELECTRONIC CONTROL MODULES 8E - 19
POWERTRAIN CONTROL MODULE (Continued)

NOTE: If the vehicle is equipped with a dual battery
system, Step 2 must be performed twice, once for
each battery.(3) Connect the voltmeter to measure between the
battery positive cable terminal clamp and the starter
solenoid B(+) terminal stud (Fig. 24). Rotate and hold
the ignition switch in the Start position. Observe the
voltmeter. If the reading is above 0.2 volt, clean and
tighten the battery positive cable eyelet terminal con-
nection at the starter solenoid B(+) terminal stud.
Repeat the test. If the reading is still above 0.2 volt,
replace the faulty battery positive cable.
NOTE: If the vehicle is equipped with a dual battery
system, Step 3 must be performed on the driver
side battery only.
Fig. 21 Fuel Shutdown Solenoid Connector - Diesel
Engine
1 - AIR TEMPERATURE SENSOR
2 - SENSOR ELECTRICAL CONNECTOR
3 - SOLENOID ELECTRICAL CONNECTOR
4 - FUEL SHUTDOWN SOLENOID
5 - INTAKE MANIFOLD (UPPER HALF)
Fig. 22 Test Battery Negative Connection
Resistance - Typical
1 - VOLTMETER
2 - BATTERY
Fig. 23 Test Battery Positive Connection Resistance
- Typical
1 - VOLTMETER
2 - BATTERY
Fig. 24 Test Battery Positive Cable Resistance -
Typical
1 - BATTERY
2 - VOLTMETER
3 - STARTER MOTOR
8F - 22 BATTERY SYSTEMBR/BE
BATTERY CABLE (Continued)

NEGATIVE CABLE INSTALLATION - GASOLINE
(1) Position the battery wire harness into the
engine compartment and under the compressor
mounting bracket, if equipped.
(2) Install and tighten the nut that secures the
battery negative cable ground eyelet terminal to the
stud on the power steering pump pivot bolt.
(3) Install the generator output cable eyelet termi-
nal onto the generator output terminal stud.
(4) Install and tighten the nut that secures the
generator output cable eyelet terminal to the genera-
tor output terminal stud. Tighten the nut to 8.4 N´m
(75 in. lbs.).
(5) Position the cover for the generator output ter-
minal stud housing onto the back of the generator
and snap it into place.
(6) Secure wire assembly in place with pushpin
retainers in there original positions.
(7) Install and tighten the screw that secures the
battery negative cable eyelet terminal to the radiator
closure panel, near the battery. Tighten the screw to
40 in. lbs.
(8) Install and tighten the screw that secures the
battery negative cable eyelet terminal to the left
front side of the frame assembly. Tighten the screw
to 80 in. lbs.
(9) Install and tighten the nut that secures the
battery positive cable eyelet terminal and the gener-
ator output cable eyelet terminal to the PDC B(+)
terminal stud. Tighten the nut to 80 in. lbs.
(10) Reconnect the battery negative cable terminal
clamp to the battery negative terminal post. Tighten
the terminal clamp pinch-bolt hex nut to 35 in. lbs.
(11)
Apply a thin coating of petroleum jelly or chassis
grease to the exposed surfaces of the battery cable ter-
minal clamps and the battery terminal posts.
BATTERY TRAY
DESCRIPTION
The battery is mounted in a molded plastic tray (Fig.
26) with an integral support located in the left front cor-
ner of the engine compartment. A U-nut held in a
molded formation on each side of the battery tray pro-
vides anchor points for the battery hold down bolts. The
battery tray is secured on the outboard side to the inner
fender shield by two hex screws with washers, and from
underneath the integral battery tray support is secured
to the left front wheelhouse inner panel by two stud
plates. Each stud plate has two studs and is secured by
two nuts with washers. The stud plate that secures the
front of the battery tray support to the wheelhouse innerpanel is installed through the wheelhouse panel from
the top. The stud plate that secures the rear of the bat-
tery tray support to the wheelhouse inner panel is
installed through the wheelhouse panel from the bottom.
A hole in the bottom of the battery tray is fitted
with a battery temperature sensor. Refer toBattery
Temperature Sensorin the index of this service
manual for the location of more information on the
battery temperature sensor. Models that are
equipped with an optional vehicle speed control sys-
tem have the speed control servo secured to the inte-
gral battery tray support. Refer toSpeed Control
Servoin the index of this service manual for the
location of more information on the speed control
servo and its mounting.
Models that are equipped with the diesel engine
option have a second battery tray located in the right
front corner of the engine compartment. This second
battery tray and its mounting are mirror image of
the standard equipment left battery tray. However,
the right battery tray and support have no provisions
for a battery temperature sensor or a speed control
servo mounting bracket.
Fig. 26 Battery Tray - Typical
1 - STUD PLATE (2)
2 - NUT AND WASHER (4)
3 - FRONT WHEELHOUSE INNER PANEL
4 - SPEED CONTROL SERVO
5 - TRAY
6 - SCREW AND WASHER (2)
7 - BATTERY TREMPERATURE SENSOR
8 - U-NUT (2)
9 - FENDER INNER SHIELD
8F - 24 BATTERY SYSTEMBR/BE
BATTERY CABLE (Continued)

OPERATION
The battery tray provides a secure mounting loca-
tion and supports the battery. On some vehicles, the
battery tray also provides the anchor point/s for the
battery holddown hardware. The battery tray and
the battery holddown hardware combine to secure
and stabilize the battery in the engine compartment,
which prevents battery movement during vehicle
operation. Unrestrained battery movement during
vehicle operation could result in damage to the vehi-
cle, the battery, or both.
REMOVAL
(1) Remove the battery from the battery tray.
Refer toBatteryin this group for the location of the
proper battery removal procedure.
(2) If the left battery tray is being removed,
remove the battery temperature sensor from the left
battery tray. Refer toBattery Temperature Sensor
in the index of this service manual for the location of
the proper battery temperature sensor removal pro-
cedures.
(3) Remove the two screws with washers that
secure the outboard side of the battery tray to the
inner fender shield (Fig. 27).(4) From the engine compartment, remove the two
nuts with washers that secure the rear of the battery
tray support to the two studs that extend through
the top of the front wheelhouse inner panel.
(5) From inside the front fender wheelhouse,
remove the two nuts with washers that secure the
front of the battery tray support to the two studs
that extend through the underside of the front wheel-
house inner panel.
(6) From inside the front fender wheelhouse,
remove the stud plate that secures the rear of the
battery tray support from the underside of the front
wheelhouse inner panel.
(7) From the engine compartment, remove the bat-
tery tray and the stud plate that secures the front of
the battery tray support from the front wheelhouse
inner panel as a unit.
(8) If the vehicle is equipped with the optional
vehicle speed control package, the speed control servo
must be removed from the left battery tray support
to complete battery tray removal. Refer toSpeed
Control Servoin the index of this service manual
for the location of the proper speed control servo
removal procedures.
INSTALLATION
(1) Clean and inspect the battery tray. Refer to
Battery Systemin this group for the location of the
proper battery tray cleaning and inspection proce-
dures.
(2) If the vehicle is equipped with the optional
vehicle speed control package, the speed control servo
must be installed onto the left battery tray support
to complete battery tray installation. Refer toSpeed
Control Servoin the index of this service manual
for the location of the proper speed control servo
installation procedures.
(3) Install the stud plate onto the front of the bat-
tery tray support.
(4) From the engine compartment, position the
battery tray and the stud plate that secures the front
of the battery tray support onto the front wheelhouse
inner panel as a unit.
(5) From inside the front fender wheelhouse,
loosely install the two nuts with washers that secure
the front of the battery tray support to the two studs
that extend through the underside of the front wheel-
house inner panel.
(6) From inside the front fender wheelhouse, posi-
tion the stud plate that secures the rear of the bat-
tery tray support onto the underside of the front
wheelhouse inner panel.
(7) From the engine compartment, loosely install
the two nuts with washers that secure the rear of the
battery tray support to the two studs that extend
through the top of the front wheelhouse inner panel.
Fig. 27 Left Battery Tray Remove/Install - Typical for
Right Battery Tray
1 - STUD PLATE (2)
2 - NUT AND WASHER (4)
3 - FRONT WHEELHOUSE INNER PANEL
4 - SPEED CONTROL SERVO
5 - TRAY
6 - SCREW AND WASHER (2)
7 - BATTERY TREMPERATURE SENSOR
8 - U-NUT (2)
9 - FENDER INNER SHIELD
BR/BEBATTERY SYSTEM 8F - 25
BATTERY TRAY (Continued)

(8) Install and tighten the two screws with wash-
ers that secure the outboard side of the battery tray
to the inner fender shield. Tighten the screws to 15.8
N´m (140 in. lbs.).
(9) Final tighten the four nuts with washers that
secure the battery tray support to the stud plates on
the front wheelhouse inner panel. Tighten the nuts
to 15.8 N´m (140 in. lbs.).(10) If the left battery tray is being installed,
install the battery temperature sensor onto the left
battery tray. Refer toBattery Temperature Sensor
in the index of this service manual for the location of
the proper battery temperature sensor installation
procedures.
(11) Install the battery onto the battery tray. Refer
toBatteryin this group for the location of the
proper battery installation procedures.
8F - 26 BATTERY SYSTEMBR/BE
BATTERY TRAY (Continued)

CHARGING
TABLE OF CONTENTS
page page
CHARGING
DESCRIPTION...........................27
OPERATION.............................27
DIAGNOSIS AND TESTING.................27
CHARGING SYSTEM....................27
SPECIFICATIONS........................28
BATTERY TEMPERATURE SENSOR
DESCRIPTION...........................29
OPERATION.............................29
REMOVAL..............................29INSTALLATION...........................29
GENERATOR
DESCRIPTION...........................29
OPERATION.............................29
REMOVAL..............................30
INSTALLATION...........................30
VOLTAGE REGULATOR
DESCRIPTION...........................31
OPERATION.............................31
CHARGING
DESCRIPTION
The charging system consists of:
²Generator
²Electronic Voltage Regulator (EVR) circuitry
within the Powertrain Control Module (PCM)
²Ignition switch (refer to Ignition System for
information)
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 the
ground 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
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.
BR/BECHARGING 8F - 27

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.
(2) Disconnect sensor pigtail harness from engine
wire harness.
(3) Pry sensor straight up from battery tray
mounting hole.
INSTALLATION
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) Feed pigtail harness through mounting hole in
top of battery tray and press sensor into top of tray
(snaps in).
(2) Connect pigtail harness.
(3) Install battery. Refer to 8A, Battery for proce-
dures.
GENERATOR
DESCRIPTION
The generator is belt-driven by the engine using a
serpentine type drive belt. It is serviced only as a
complete assembly. If the generator fails for any rea-
son, the entire assembly must be replaced.
OPERATION
As the energized rotor begins to rotate within the
generator, the spinning magnetic field induces a cur-
rent into the windings of the stator coil. Once the
generator begins producing sufficient current, it also
provides the current needed to energize the rotor.
The Y type stator winding connections deliver the
induced alternating current to 3 positive and 3 neg-
ative diodes for rectification. From the diodes, recti-
fied direct current is delivered to the vehicle
electrical system through the generator battery ter-
minal.
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 - 29

CAUTION: When installing a serpentine accessory
drive belt, the belt MUST be routed correctly. The
water pump will be rotating in the wrong direction if
the belt is installed incorrectly, causing the engine
to overheat. Refer to belt routing label in engine
compartment, or refer to Belt Schematics in Group
7, Cooling System.
(4) Install generator drive belt. Refer to 7, Cooling
System for procedure.(5) Install negative battery cable(s) to battery(s).
VOLTAGE REGULATOR
DESCRIPTION
The Electronic Voltage Regulator (EVR) is not a
separate component. It is actually a voltage regulat-
ing circuit located within the Powertrain Control
Module (PCM). The EVR is not serviced separately. If
replacement is necessary, the PCM must be replaced.
OPERATION
The amount of direct current produced by the gen-
erator is controlled by EVR circuitry contained
within the PCM. This circuitry is connected in series
with the generators second rotor field terminal and
its ground.
Voltage is regulated by cycling the ground path to
control the strength of the rotor magnetic field. The
EVR circuitry monitors system line voltage (B+) and
battery temperature (refer to Battery Temperature
Sensor for more information). It then determines a
target charging voltage. If sensed battery voltage is
0.5 volts or lower than the target voltage, the PCM
grounds the field winding until sensed battery volt-
age is 0.5 volts above target voltage. A circuit in the
PCM cycles the ground side of the generator field up
to 100 times per second (100Hz), but has the capabil-
ity to ground the field control wire 100% of the time
(full field) to achieve the target voltage. If the charg-
ing rate cannot be monitored (limp-in), a duty cycle
of 25% is used by the PCM in order to have some
generator output. Also refer to Charging System
Operation for additional information.
Fig. 4 Remove/Install GeneratorÐDiesel Engine
1 - UPPER MOUNTING BOLT
2 - BRACKET-TO-ENGINE BOLT
3 - LOWER MOUNTING BOLT/NUT
4 - GENERATOR
Fig. 5 Generator ConnectorsÐTypical Bosch
1 - FIELD WIRE CONNECTOR
2 - FIELD WIRES
3 - B+ (OUTPUT TERMINAL)
Fig. 6 Generator ConnectorsÐTypical Denso
1 - FIELD WIRES
2 - B+ (OUTPUT TERMINAL)
3 - FIELD WIRE CONNECTOR
BR/BECHARGING 8F - 31
GENERATOR (Continued)

OPERATION
The heated seat module receives fused battery cur-
rent through the energized heated seat relay in the
Junction Block (JB) only when the engine is running.
The heated seat switches receive battery current
through a fused ignition switch output (run) circuit
only when the ignition switch is in the On position.
The heated seat module shares a common ground cir-
cuit with each of the heated seat elements. The
heated seat elements will only operate when the sur-
face temperature of the seat cushion cover at the
heated seat sensors is below the designed tempera-
ture set points of the system.
The heated seat module will automatically turn off
the heated seat elements if it detects a short in the
heated seat element circuit or a heated seat sensor
value that is out of range. The heated seat system
will also be turned off automatically whenever the
ignition switch is turned to any position except On or
if the engine quits running. If the ignition switch is
turned to the Off position or if the engine quits run-
ning while a heated seat is turned ON, the heated
seat will remain Off after the engine is restarted
until a heated seat switch is depressed again.
The heated seat module monitors inputs from the
heated seat sensors and the heated seat switches. In
response to these inputs the heated seat module uses
its internal programming to control outputs to the
heated seat elements in both front seats and to con-
trol the heated seat LED indicator lamps located in
both of the heated seat switches. The heated seat
module is also programmed to provide a self-diagnos-
tic capability. When the module detects certain fail-
ures within the heated seat system, it will provide a
visual indication of the failure by flashing the indica-
tor lamps in the heated seat switches.
DIAGNOSIS & TESTING - HEATED SEAT
SYSTEM
SELF-DIAGNOSIS
The heated seat system is capable of performing
some self-diagnostics. The following table depicts the
various failure modes which will be reported to the
vehicle operator or technician by flashing the individ-
ual heated seat switch Light Emitting Diode (LED)
indicator lamps. See the Heated Seat System Self-Di-
agnosis table for the diagnostic routines. The driver
side heated seat switch indicator lamps will flash if a
failure occurs in the driver side heated seat, and the
passenger side heated seat switch indicator lamps
will flash for a passenger side heated seat failure. If
a monitored heated seat system failure occurs, the
switch indicator lamps will flash at a pulse rate of
about one-half second on, followed by about one-half
second off for a duration of about one minute afterthe switch for the faulty heated seat is depressed in
either the Low or High direction. This process will
repeat every time the faulty heated seat switch is
actuated until the problem has been corrected.
Heated Seat System Self-Diagnosis
Monitored FailureSwitch High
Indicator LampSwitch Low
Indicator Lamp
Heated Seat
Element ShortedFlashing Flashing
Heated Seat
Element OpenFlashing Off
Heated Seat
Sensor Value Out
of RangeOff Flashing
TESTING
Refer toPower Seatin the index of this service
manual for the location of complete heated seat sys-
tem wiring diagrams. Before testing the individual
components in the heated seat system, perform the
following preliminary checks:
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
²If the heated seat switch back lighting and the
cluster illumination lamps do not illuminate with the
headlamps or park lamps turned On, refer toInstru-
ment Clusterin the index of this service manual for
the location of the proper cluster illumination lamps
diagnosis and testing procedures. If the heated seat
switch back lighting does not illuminate, but the
cluster illumination lamps do illuminate with the
headlamps or park lamps turned On, refer to
Heated Seat Switchin this section for the location
of the proper heated seat switch diagnosis and test-
ing procedure.
²If a single indicator lamp for one heated seat
switch does not operate and the heated seat elements
do heat, refer toHeated Seat Switchin this section
for the location of the proper heated seat switch diag-
nosis and testing procedure.
8G - 6 HEATED SEAT SYSTEMBR/BE
HEATED SEAT SYSTEM (Continued)