Front wiring DODGE RAM 1500 1998 2.G User Guide

pigtail wires are also captured between a covering
and the adhesive foam rubber backing. The heated
seat sensors are Negative Thermal Coefficient (NTC)
thermistors. The sensors for both front seats receive
a voltage feed from a single output of the heated seat
module, but the module receives individual sensor
inputs from the driver side and passenger side sen-
sors.
The heated seat elements and sensors should not
be repaired. If damaged or faulty, the heated seat ele-
ment assembly must be replaced.
OPERATION
One end of the heated seat element resistor wire is
connected to ground at all times through a splice in
the heated seat module ground circuit. Battery cur-
rent is directed to the other end of the heated seat
element resistor wire by the energized N-channel
Field Effect Transistor (N-FET) located within the
heated seat module. The heated seat module will
energize the N-FET only when the heated seat
switch is in the Low or High position and the heated
seat sensor indicates that the seat cushion surface
temperature is below the selected (Low or High) tem-
perature set point. As electrical current passes
through the heating element grid, the resistance of
the wire used in the element disperses some of that
electrical current in the form of heat. The heat pro-
duced by the heated seat element grid then radiates
through the seat trim cover, warming its occupant.
The resistance of the heated seat sensor increases
and decreases as the surface temperature of the seat
cushion cover changes. The heated seat module sup-
plies each sensor with a 5v voltage feed, then uses
the sensor resistance to determine when the heated
seat element grids need to be cycled on or off in order
to maintain the selected temperature set point.
DIAGNOSIS AND TESTING - HEATED SEAT
ELEMENT
The heated seat module will self-diagnose shorted
or open heated seat element circuits and sensor cir-
cuits. Refer to Heated Seat System Diagnosis and
Testing in this section for additional diagnosis and
testing procedures. To manually check the heated
seat element, proceed as follows. The wire harness
connectors for the seat cushion and seat back heating
elements and sensor are located on the right side of
the seat, near the edge of the seat cushion frame.
The proper connector can be identified by the foam
wrapping.
NOTE: When checking heated seat elements for
continuity, be certain to move the heating element
being checked. Moving the element, such as sitting
in the seat will eliminate the possibility of an inter-mittent open in the element which would only be
evident if the element was in a certain position.
Failure to check the element in various positions
could result in an incomplete test.
(1) Position the appropriate seat in the full for-
ward position.
(2) Make certain the ignition switch is in the OFF
position.
(3) Disconnect the heated seat element connector
which requires testing. Check for continuity between
the two heated seat element circuit cavities while
moving the appropriate seat cushion. Refer toWir-
ingfor the location of complete heated seat system
wiring diagrams. There should be continuity. If OK,
the elements within the seat assembly test OK, go to
Step 4. If not OK, replace the faulty seat heating ele-
ment, refer to the procedure in this section.
(4) Test the seat wire harness between the heated
seat module connector and the appropriate heated
seat wire harness connector for shorted or open cir-
cuits. If OK, element is OK, proceed with testing the
heated seat sensor and module. If not OK, repair the
shorted or open seat wire harness as required.
REMOVAL
Do not remove the heating element from the seat
or seat back cushion. The original element is perma-
nently attached to the seat cushions and cannot be
removed without damaging the cushion. The replace-
ment heating element is designed to be applied
directly over the original seat heating element.
(1) Disconnect and isolate the negative battery
cable.
(2) Remove the appropriate seat cushion or seat
back trim cover. Refer to the Body section of this
manual for the procedures.
(3) Disconnect the inoperative heated seat cushion
or seat back element electrical connectors.
(4) Locate the wires leading from the inoperative
heating element and cut them off flush with the edge
of the original heating element.
INSTALLATION
(1) Peel off the adhesive backing on the back of the
replacement heating element and stick directly over
the original heating element (Fig. 3).
CAUTION: During the installation of the replace-
ment heating element, be careful not to fold or
crease the element assembly. Folds or creases will
cause premature failure.
(2) Connect the new heating element electrical
connectors (Fig. 2).
(3) Connect the battery negative cable.
(4) Verify heated seat system operation.
8G - 10 HEATED SEAT SYSTEMDR
HEATED SEAT ELEMENT (Continued)

(5) Install the appropriate seat cushion or seat
back trim cover. Make certain the seat wire harness
is correctly routed through the seat and seat back.
HEATED SEAT SENSOR
DESCRIPTION
The heated seat temperature sensor is a Negative
Temperature Coefficient (NTC) thermistor. One tem-
perature sensor is used for each seat. This tempera-
ture sensor is located in the seat cushion heating
element on all models.
The heated seat temperature sensor cannot be
repaired or adjusted and must be replaced if defec-
tive. The heated seat cushion element must be
replaced if the temperature sensor is defective. Refer
to the procedure in this section of the service man-
ual.
OPERATION
When the temperature of the seat cushion cover
rises, the resistance of the sensor decreases. The
heated seat module supplies five-volts to one side of
each sensor, and monitors the voltage drop through
the sensor on a return circuit. The heated seat mod-
ule uses this temperature sensor input to monitor
the temperature of the seat, and regulates the cur-
rent flow to the seat heating elements accordingly.
DIAGNOSIS AND TESTING - HEATED SEAT
SENSOR
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 val-
ues generated may not be the same as the results
shown here, or may have to be converted to the
range used here.
(1) Position the driver seat in the full rearward
position.
(2) Unclip the heated seat module from the bottom
of the drivers seat cushion pan.
(3) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity (#7
for passenger, #8 for driver seat) for a range in volt-
age from approx. 1.72 ± 3.0 volts. It should be within
this range, If OK check the heated seat element. If
NOT OK, check for the proper 5 volt supply to the
heated seat sensor, from the module. Refer to Wiring
for specific information. If 5 volts is not being sup-
plied to the sensor from the module, replace the
heated seat module.
(4) Test the seat wire harness between the heated
seat module connector and the heated seat wire har-
ness connector for shorted or open circuits. If OK,
refer toDiagnosis and Testing the Heated Seat
Modulein Electronic Control Modules, for the
proper heated seat module diagnosis and testing pro-
cedures. If not OK, repair the shorted or open heated
seat wire harness as required.
REMOVAL
(1) For heated seat sensor replacement procedure
(Refer to 8 - ELECTRICAL/HEATED SEATS/
HEATED SEAT ELEMENT - REMOVAL).
HEATED SEAT SWITCH
DESCRIPTION
The momentary, bidirectional rocker-type heated
seat switch (Fig. 4) provides a resistor-multiplexed
signal to the heated seat module via a 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 pre-
ferred 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
Fig. 3 Heating Element Installation
1 - ORIGINAL (INOPERATIVE) HEATING ELEMENT
2 - REPLACEMENT HEATING ELEMENT
DRHEATED SEAT SYSTEM 8G - 11
HEATED SEAT ELEMENT (Continued)

The heated seat module is an electronic micropro-
cessor controlled device designed and programmed to
use inputs from the battery, 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 per-
form self-diagnosis of certain heated seat system
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 integrated power module.
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 con-
trols battery current feeds to the heated seat ele-
ments and sensors, and controls the ground for the
heated seat switch indicator lamps.
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.
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
toDiagnosis and Testing Heated Seat Systemin
Heated Seats for the location of flashing LED heated
seat system diagnosis and testing procedures. If a
heated seat heats but one or both indicator lamps on
the heated seat switch fail to operate, test the heated
seat switch. Refer toDiagnosis and Testing
Heated Seat Switchin Heated Seats for heated
seat switch diagnosis and testing procedures. If the
heated seat switch checks OK, proceed as follows.
(1) Check the heated seat element (Refer to 8 -
ELECTRICAL/HEATED SEATS/HEATED SEAT
ELEMENT - DIAGNOSIS AND TESTING).
(2) Check the heated seat sensor (Refer to 8 -
ELECTRICAL/HEATED SEATS/HEATED SEAT
SENSOR - DIAGNOSIS AND TESTING).
(3) Check the heated seat switch (Refer to 8 -
ELECTRICAL/HEATED SEATS/DRIVER HEATED
SEAT SWITCH - DIAGNOSIS AND TESTING).
NOTE: Refer to Wiring for the location of complete
heated seat system wiring diagrams and connector
pin-out information.
(4) Using a voltmeter, backprobe the appropriate
heated seat module connector, do not disconnect.
Check for voltage at the appropriate pin cavities. 12v
Fig. 5 Heated Seat Module
1 - MOUNTING TABS (NOT USED ON DR)
2 - HEATED SEAT MODULE
3 - ELECTRICAL CONNECTOR RECEPTACLE
8G - 14 HEATED SEAT SYSTEMDR
HEATED SEAT MODULE (Continued)

for more than about 1.6 kilometers (one mile) and
the vehicle speed remains greater than about twenty-
four kilometers-per-hour (fifteen miles-per-hour).
²Vacuum Fluorescent Display Synchroniza-
tion- The EMIC transmits electronic panel lamp
dimming level messages which allows all other elec-
tronic modules on the PCI data bus with Vacuum
Fluorescent Display (VFD) units to coordinate their
illumination intensity with that of the EMIC VFD
units.
²Vehicle Theft Security System- The EMIC
monitors inputs from the door cylinder lock
switch(es), the door ajar switches, the ignition
switch, and the Remote Keyless Entry (RKE) receiver
module, then provides electronic horn and lighting
request messages to the Front Control Module (FCM)
located on the Integrated Power Module (IPM) for
the appropriate VTSS alarm output features.
²Wiper/Washer System Control- The EMIC
provides electronic wiper and/or washer request mes-
sages to the Front Control Module (FCM) located on
the Integrated Power Module (IPM) for the appropri-
ate wiper and washer system features. (Refer to 8 -
ELECTRICAL/WIPERS/WASHERS - DESCRIP-
TION).
The EMIC houses six analog gauges and has pro-
visions for up to twenty-three indicators (Fig. 3) or
(Fig. 4). The EMIC includes the following analog
gauges:
²Coolant Temperature Gauge
²Fuel Gauge
²Oil Pressure Gauge
²Speedometer
²Tachometer
²Voltage Gauge
Some of the EMIC indicators are automatically
configured when the EMIC is connected to the vehi-
cle electrical system for compatibility with certain
optional equipment or equipment required for regula-
tory purposes in certain markets. While each EMIC
may have provisions for indicators to support every
available option, the configurable indicators will not
be functional in a vehicle that does not have the
equipment that an indicator supports. The EMIC
includes provisions for the following indicators (Fig.
3) or (Fig. 4):
²Airbag Indicator (with Airbag System only)
²Antilock Brake System (ABS) Indicator
(with ABS or Rear Wheel Anti-Lock [RWAL]
brakes only)
²Brake Indicator
²Cargo Lamp Indicator
²Check Gauges Indicator
²Cruise Indicator (with Speed Control only)
²Door Ajar Indicator²Electronic Throttle Control (ETC) Indicator
(with 5.7L Gasoline Engine only)
²Gear Selector Indicator (with Automatic
Transmission only)
²High Beam Indicator
²Lamp Out Indicator
²Low Fuel Indicator
²Malfunction Indicator Lamp (MIL)
²Seatbelt Indicator
²Security Indicator (with Sentry Key Immo-
bilizer & Vehicle Theft Security Systems only)
²Service Four-Wheel Drive Indicator (with
Four-Wheel Drive only)
²Tow/Haul Indicator (with Automatic Trans-
mission only)
²Transmission Overtemp Indicator (with
Automatic Transmission only)
²Turn Signal (Right and Left) Indicators
²Upshift Indicator (with Manual Transmis-
sion only)
²Washer Fluid Indicator
²Wait-To-Start Indicator (with Diesel Engine
only)
²Water-In-Fuel Indicator (with Diesel Engine
only)
Each indicator in the EMIC, except those located
within one of the VFD units, is illuminated by a ded-
icated LED that is soldered onto the EMIC electronic
circuit board. The LED units are not available for
service replacement and, if damaged or faulty, the
entire EMIC must be replaced. Cluster illumination
is accomplished by dimmable incandescent back
lighting, which illuminates the gauges for visibility
when the exterior lighting is turned on. Each of the
incandescent bulbs is secured by an integral bulb
holder to the electronic circuit board from the back of
the cluster housing.
Hard wired circuitry connects the EMIC to the
electrical system of the vehicle. These hard wired cir-
cuits are integral to several wire harnesses, which
are routed throughout the vehicle and retained by
many different methods. These circuits may be con-
nected to each other, to the vehicle electrical system
and to the EMIC through the use of a combination of
soldered splices, splice block connectors, and many
different types of wire harness terminal connectors
and insulators. Refer to the appropriate wiring infor-
mation. The wiring information includes wiring dia-
grams, proper wire and connector repair procedures,
further details on wire harness routing and reten-
tion, as well as pin-out and location views for the
various wire harness connectors, splices and grounds.
The EMIC modules for this model are serviced only
as complete units. The EMIC module cannot be
adjusted or repaired. If a gauge, an LED indicator, a
VFD unit, the electronic circuit board, the circuit
DRINSTRUMENT CLUSTER 8J - 5
INSTRUMENT CLUSTER (Continued)

MARKER LAMP UNIT
REMOVAL
REMOVAL - FENDER MARKER LAMP......17
REMOVAL - TAILGATE MARKER LAMP.....18
INSTALLATION
INSTALLATION - FENDER MARKER LAMP . . 18
INSTALLATION - TAILGATE MARKER LAMP . 18
MULTI-FUNCTION SWITCH
DESCRIPTION - TURN SIGNAL SYSTEM.....18
OPERATION - TURN SIGNAL SYSTEM.......18
DIAGNOSIS AND TESTING - MULTI-
FUNCTION SWITCH...................18
REMOVAL.............................19
INSTALLATION.........................19
PARK LAMP RELAY
DESCRIPTION.........................20
OPERATION...........................20
DIAGNOSIS AND TESTING - PARK LAMP
RELAY..............................20
REMOVAL.............................21
INSTALLATION.........................21
PARK/TURN SIGNAL LAMP
REMOVAL.............................21
INSTALLATION.........................21
TAIL LAMP
REMOVAL
REMOVAL - WITH CARGO BOX..........22REMOVAL - WITHOUT CARGO BOX.......22
INSTALLATION
INSTALLATION - WITH CARGO BOX.......22
INSTALLATION - WITHOUT CARGO BOX . . . 22
TAIL LAMP UNIT
REMOVAL
REMOVAL - WITH CARGO BOX..........22
REMOVAL - WITHOUT CARGO BOX.......23
INSTALLATION
INSTALLATION - WITH CARGO BOX.......23
INSTALLATION - WITHOUT CARGO BOX . . . 23
TRAILER TOW WIRING
DESCRIPTION.........................24
TURN LAMP
REMOVAL
REMOVAL - WITH CARGO BOX..........24
REMOVAL - WITHOUT CARGO BOX.......24
INSTALLATION
INSTALLATION - WITH CARGO BOX.......24
INSTALLATION - WITHOUT CARGO BOX . . . 24
UNDERHOOD LAMP
REMOVAL.............................25
INSTALLATION.........................25
UNDERHOOD LAMP UNIT
REMOVAL.............................25
INSTALLATION.........................25
LAMPS/LIGHTING - EXTERIOR
DESCRIPTION
The exterior lighting system for this model include
the following components:
²Backup Lamps
²Brake Lamps
²Daytime Running Lamps
²Front Fog Lamps
²Hazard Warning Lamps
²Headlamps
²Park Lamps
²Turn Signal Lamps
Other components of the exterior lighting system
for this model include:
²Backup Lamp Switch
²Brake Lamp Switch
²Front Control Module
²Front Fog Lamp Relay
²Hazard Switch
²Multi-Function Switch
²Park Lamp Relay
²Trailer Tow Connectors
Some of the interior and exterior lighting functions
are governed by the front control module. The head-
lamp, dome, and door ajar switchs provide signals to
the instrument cluster. The instrument cluster sends
a J1850 message to the front control module to
enable the necessary components for illumination.Hard wired circuitry connects the exterior lighting
system components to the electrical system of the
vehicle. Refer to the appropriate wiring information.OPERATION
DAYTIME RUNNING LAMPS
Power is reduced using pulse-width modulation to
the high beams, where by the power is switched on
and off rapidly instead of remaining on continuously.
The duration and interval of the power pulses is pro-
grammed into the Front Control Module (FCM).
HEADLAMP SYSTEM
The instrument cluster monitors both the multi-
plexed headlamp and multifunction switches. The
instrument cluster transmits a J1850 bus message to
the front control module (FCM) to activate the head-
lamps. The headlamp system will default to head-
lamps ON position when ignition switch is ON and
when an open or short circuit failure occurs on the
headlamp switch input to the instrument cluster. The
system will return to normal operation when the
open or short is repaired. A fault will be reported by
the Instrument Cluster when a failure occurs on the
dimmer or headlamp switch input.
If the exterior lamps are ON, and the headlamp
switch is in any position other than OFF, with the
ignition switch OFF (LOCK) after 5 minutes, the
8L - 2 LAMPS/LIGHTING - EXTERIORDR

HEADLAMP DIAGNOSIS
CONDITION POSSIBLE CAUSES CORRECTION
HEADLAMPS ARE DIM
WITH ENGINE IDLING
OR IGNITION TURNED
OFF1. Loose or corroded battery
cables.1. Clean and secure battery cable clamps and
posts.
2. Loose or worn generator drive
belt.2. Adjust or replace generator drive belt.
3. Charging system output too low. 3. Test and repair charging system, refer to
Electrical, Charging
4. Battery has insufficient charge. 4. Test battery state-of-charge, refer to
Electrical, Battery System.
5. Battery is sulfated or shorted. 5. Load test battery, refer to Electrical, Battery
System.
6. Poor lighting circuit ground. 6. Test for voltage drop across ground circuits,
refer to Electrical, Wiring Diagram Information.
HEADLAMP BULBS
BURN OUT
FREQUENTLY1. Integrated Control Module (ICM)
not controlling voltage.1. Test and repair Integrated Control Module.
2. Loose or corroded terminals or
splices in circuit.2. Inspect and repair all connectors and splices.
Refer to Electrical, Wiring Information.
HEADLAMPS ARE DIM
WITH ENGINE
RUNNING ABOVE IDLE1. Charging system output too low. 1. Test and repair charging system, refer to
Electrical, Wiring Information.
2. Poor lighting circuit ground. 2. Test for voltage drop across ground circuits,
refer to Electrical, Wiring Information.
3. High resistance in headlamp
circuit.3. Test amperage draw of headlamp circuit.
HEADLAMPS FLASH
RANDOMLY1. Poor lighting circuit ground. 1. Test for voltage drop across ground
locations, refer to Electrical, Wiring Information.
2. Variable resistance in headlamp
circuit.2. Test amperage draw of headlamp circuit.
3. Loose or corroded terminals or
splices in circuit.3. Inspect and repair all connectors and splices,
refer to Electrical, Wiring Information.
4. Faulty headlamp switch. 4. Replace headlamp switch.
5. Front Control Module
Malfunction.5. Refer to appropriate ICM/FCM diagnostics.
8L - 4 LAMPS/LIGHTING - EXTERIORDR
LAMPS/LIGHTING - EXTERIOR (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
HEADLAMPS DO NOT
ILLUMINATE1. No voltage to headlamps. 1. Repair open headlamp circuit, refer to
Electrical, Wiring Information.
2. No ground at headlamps. 2. Repair circuit ground, refer to Electrical,
Wiring Information.
3. Broken connector terminal or
wire splice in headlamp circuit.3. Repair connector terminal or wire splice.
4. Faulty or burned out bulb. 4. Replace headlamp bulb(s).
5. Integrated Control Module
malfunction.5. Refer to appropriate Body Control Module
diagnostics.
6. J1850 Bus Communication 6. Verify messages being transmitted by
Instrument Cluster and received by FCM.
7. Front Control Module
Malfunction.7. Refer to appropriate ICM/FCM diagnostics.
HEADLAMPS ON WITH
IGNITION IN RUN, WITH
HEADLAMP SWITCH
OFF1. Faulty headlamp switch. 1. Replace headlamp switch (review Instrument
Cluster logged faults).
2. Diagnostic tool indicates (4.7 -
5.0V) on headlamp switch input to
Instrument Cluster.2. Inspect and repair terminals, connectors and
open circuits.
3. J1850 Bus Communication. 3. Verify messages being transmitted by
Instrument Cluster and received by FCM.
4. Front Control Module
Malfunction.4. Refer to appropriate ICM/FCM diagnostics.
FOG LAMP DIAGNOSIS
CONDITION POSSIBLE CAUSES CORRECTION
FOG LAMPS ARE DIM
WITH ENGINE IDLING
OR IGNITION TURNED
OFF.1. Loose or corroded battery
cables.1. Clean and secure battery cable clamps and
posts.
2. Loose or worn generator drive
belt.2. Adjust or replace generator drive belt.
3. Charging system output too low. 3. Test and repair charging system. Refer to
Electrical, Charging,
4. Battery has insufficient charge. 4. Test battery state-of-charge. Refer to
Electrical, Battery System.
5. Battery is sulfated or shorted. 5. Load test battery. Refer to Electrical, Battery
System.
6. Poor lighting circuit ground. 6. Test for voltage drop across ground
locations. Refer to Electrical, Wiring
Information.
FOG LAMP BULBS
BURN OUT
FREQUENTLY1. Charging system output too
high.1. Test and repair charging system. Refer to
Electrical, Charging.
2. Loose or corroded terminals or
splices in circuit.2. Inspect and repair all connectors and splices.
Refer to Electrical, Wiring Information.
DRLAMPS/LIGHTING - EXTERIOR 8L - 5
LAMPS/LIGHTING - EXTERIOR (Continued)

ment of the vehicle. The front fog lamp relay is a
conventional International Standards Organization
(ISO) micro relay (Fig. 9). Relays conforming to the
ISO specifications have common physical dimensions,
current capacities, terminal patterns, and terminal
functions. The relay is contained within a small, rect-
angular, molded plastic housing and is connected to
all of the required inputs and outputs by five integral
male spade-type terminals that extend from the bot-
tom of the relay base.
The front fog lamp relay cannot be adjusted or
repaired and, if faulty or damaged, the unit must be
replaced.
OPERATION
The front fog lamp relay is an electromechanical
switch that uses a low current input from the Front
Control Module (FCM) to control a high current out-
put to the front fog lamps. The movable common feed
contact point is held against the fixed normally
closed contact point by spring pressure. When the
relay coil is energized, an electromagnetic field is
produced by the coil windings. This electromagnetic
field draws the movable relay contact point away
from the fixed normally closed contact point, and
holds it against the fixed normally open contact
point. When the relay coil is de-energized, spring
pressure returns the movable contact point back
against the fixed normally closed contact point. A
resistor is connected in parallel with the relay coil in
the relay, and helps to dissipate voltage spikes and
electromagnetic interference that can be generated as
the electromagnetic field of the relay coil collapses.
The front fog lamp relay terminals are connected
to the vehicle electrical system through a connector
receptacle in the Power Distribution Center (PDC).
The inputs and outputs of the front fog lamp relay
include:
²Common Feed Terminal- The common feed
terminal (30) receives battery voltage at all times
from a fuse in the PDC through a fused B(+) circuit.
²Coil Ground Terminal- The coil ground termi-
nal (85) is connected to a control output of the Front
Control Module (FCM) through a front fog lamp relay
control circuit. The FCM controls front fog lamp oper-
ation by controlling a ground path through this cir-
cuit.
²Coil Battery Terminal- The coil battery ter-
minal (86) receives battery voltage at all times from
a fuse in the PDC through a fused B(+) circuit.
²Normally Open Terminal- The normally open
terminal (87) is connected to the front fog lamps
through a front fog lamp relay output circuit and
provides battery voltage to the front fog lamps when-
ever the relay is energized.²Normally Closed Terminal- The normally
closed terminal (87A) is not connected in this appli-
cation.
The front fog lamp relay can be diagnosed using
conventional diagnostic tools and methods. Refer to
the appropriate wiring information for diagnosis and
testing of the front fog lamp micro-relay and for com-
plete wiring diagrams.
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, SEAT BELT TENSIONER,
FRONT IMPACT SENSORS, SIDE CURTAIN AIRBAG,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-
THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the cover for the Power Distribution
Center (PDC).
(3) Remove the front fog lamp relay by grasping it
firmly and pulling it straight out from the receptacle
in the PDC.
INSTALLATION
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, SEAT BELT TENSIONER,
FRONT IMPACT SENSORS, SIDE CURTAIN AIRBAG,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-
THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
DRLAMPS/LIGHTING - EXTERIOR 8L - 13
FOG LAMP RELAY (Continued)

REMOVAL - TAILGATE MARKER LAMP
(1) Remove the two screws that secure the lens
assembly to the tailgate (Fig. 15).
(2) Turn the bulb sockets counterclockwise a quar-
ter turn and remove the bulb sockets from the lens
assembly.
INSTALLATION
INSTALLATION - FENDER MARKER LAMP
(1) Install the bulb socket to the lens assembly.
Turn the bulb socket a quarter turn clockwise.
(2) Position the lens assembly against the fender.
Using firm pressure, push the lens assembly into the
fender.
INSTALLATION - TAILGATE MARKER LAMP
(1) Install the bulb sockets into the lens assembly.
Turn the bulb sockets a quarter turn clockwise.(2) Position the lens assembly to the tailgate.
Install and tighten the two screws securely.
MULTI-FUNCTION SWITCH
DESCRIPTION - TURN SIGNAL SYSTEM
The multi-function switch is a resistive MUX
switch that is monitored by the Instrument Cluster.
The turn signals are actuated with the lever on
Multi-Function Switch. The signals are automatically
turned off by a canceling cam (two lobes molded to
the back of the clock spring mechanism). The cam
comes in contact with the cancel actuator on the turn
signal (multi-function) switch assembly. Either cam
lobe, pushing on the cancel actuator, returns the
switch to the OFF position.
OPERATION - TURN SIGNAL SYSTEM
The Instrument Cluster monitors the multiplexed
multifunction switch. In a turning event the Instru-
ment Cluster senses a change in the turn signal
lever and illuminates the appropriate turn signal
indicator. At the same time, the Instrument Cluster
will send a J1850 message on the PCI bus to the
Front Control Module (FCM). The FCM will respond
by activating the appropriate relay in the Power Dis-
tribution Center.
A chime will sound after the turn is completed if
vehicle has traveled a distance of approximately 1.0
mile and a speed of 15 mph, with the turn signal ON.
DIAGNOSIS AND TESTING - MULTI-FUNCTION
SWITCH
To test the turn signal, headlamp beam select and
optical horn portion of the multi-function switch:
(1) Remove the multi-function switch, refer to
Electrical, Lamps/Lighting - Exterior, Multi-Function
Switch, Removal, and Installation.
(2) Using an ohmmeter check the resistance read-
ings between multi-function switch pins. Refer to
Wiring Diagrams for proper pin numbers and the
MULTI-FUNCTION SWITCH TESTS table.
MULTI-FUNCTION SWITCH TESTS
EXTERIOR LIGHTING FUNCTIONS
SWITCH POSITION CONNECTOR PINS RESISTANCE (OHMS)
Off 1 - 2 Open
Headlamp High Beams On 1 - 2 518 - 575
Hazard 3 - 2 115 - 128
Fig. 15 Tailgate Marker Lamp Housing
1 - RETAINING NUT (2)
2 - TAILGATE
3 - WIRING HARNESS AND BULB SOCKET
4 - SCREW (2)
5 - LENS ASSEMBLY
8L - 18 LAMPS/LIGHTING - EXTERIORDR
MARKER LAMP UNIT (Continued)

PARK LAMP RELAY
DESCRIPTION
The park lamp relay is located in the Power Dis-
tribution Center (PDC) of the vehicle. The park lamp
relay is a conventional International Standards
Organization (ISO) micro relay (Fig. 17). Relays con-
forming to the ISO specifications have common phys-
ical dimensions, current capacities, terminal
patterns, and terminal functions.
The park lamp relay cannot be adjusted or
repaired and, if faulty or damaged, the unit must be
replaced.
OPERATION
The park lamp relay is an electromechanical
switch that uses a low current input from the Front
Control Module (FCM) to control a high current out-
put to the park lamps. The movable common feed
contact point is held against the fixed normally
closed contact point by spring pressure. When the
relay coil is energized, an electromagnetic field is
produced by the coil windings. This electromagnetic
field draws the movable relay contact point away
from the fixed normally closed contact point, and
holds it against the fixed normally open contact
point. When the relay coil is de-energized, spring
pressure returns the movable contact point back
against the fixed normally closed contact point. A
resistor is connected in parallel with the relay coil in
the relay, and helps to dissipate voltage spikes and
electromagnetic interference that can be generated as
the electromagnetic field of the relay coil collapses.The park lamp relay terminals are connected to
the vehicle electrical system through a connector in
the Junction Block (JB). The inputs and outputs of
the headlamp low beam relay include:
²Common Feed Terminal- The common feed
terminal (30) is connected to the park lamps through
the park lamp relay output circuit and provides
ground to the park lamps when the relay is de-ener-
gized, and battery current to the park lamps when-
ever the relay is energized.
²Coil Ground Terminal- The coil ground termi-
nal (85) is connected to a control output of the Front
Control Module (FCM) through a park lamp relay
control circuit. The FCM controls park lamp opera-
tion by controlling a ground path through this cir-
cuit.
²Coil Battery Terminal- The coil battery ter-
minal (86) receives battery current at all times from
a fuse in the PDC through a fused B(+) circuit.
²Normally Open Terminal- The normally open
terminal (87) receives battery current at all times
from a fuse in the Power Distribution Center (PDC)
through a fused B(+) circuit.
²Normally Closed Terminal- The normally
closed terminal (87A) is connected to ground at all
times.
The park lamp relay can be diagnosed using con-
ventional diagnostic tools and methods.
DIAGNOSIS AND TESTING - PARK LAMP
RELAY
The park lamp relay (Fig. 18) is located in the
Power Distribution Center (PDC). Refer to the appro-
priate wiring information.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, SEAT BELT TENSIONER,
FRONT IMPACT SENSORS, SIDE CURTAIN AIRBAG,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-
THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
(1) Remove the park lamp relay from the PDC.
(2) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
Fig. 17 ISO Micro Relay
30 - COMMON FEED
85 - COIL GROUND
86 - COIL BATTERY
87 - NORMALLY OPEN
87A - NORMALLY CLOSED
8L - 20 LAMPS/LIGHTING - EXTERIORDR