fuse DODGE RAM 2001 Service Workshop Manual

(3) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Remove the instrument cluster from the instrument
panel. Check for continuity between the 4WD switch
sense circuit cavities of the instrument panel wire
harness connector (Connector C2) for the instrument
cluster and the engine wire harness connector for the
four-wheel drive switch. There should be continuity.
If OK, replace the faulty instrument cluster. If not
OK, repair the open 4WD switch sense circuit
between the instrument cluster and the four-wheel
drive switch as required.
INDICATOR STAYS ILLUMINATED WITH FOUR-WHEEL DRIVE
MODE NOT SELECTED
(1) Disconnect and isolate the battery negative
cable. Disconnect the engine wire harness connector
for the four-wheel drive switch from the switch con-
nector receptacle. Check for continuity between the
ground circuit terminal and the 4WD switch sense
circuit terminal in the four-wheel drive switch con-
nector receptacle. There should be no continuity. If
OK, repair the shorted 4WD switch sense circuit
between the four-wheel drive switch and the instru-
ment cluster as required. If not OK, replace the
faulty four-wheel drive switch.
SPEEDOMETER
DESCRIPTION
A speedometer is standard equipment on all instru-
ment clusters. The speedometer is located just to the
right of the tachometer near the center of the instru-
ment cluster. The speedometer consists of a movable
gauge needle or pointer controlled by the instrument
cluster circuitry and a fixed 210 degree primary scale
on the gauge dial face that reads left-to-right either
from 0 to 120 mph, or from 0 to 200 km/h, depending
upon the market for which the vehicle is manufac-
tured. Each version also has a secondary inner scale
on the gauge dial face that provides the equivalent
opposite units from the primary scale. Text appearing
on the cluster overlay just below the hub of the
speedometer needle abbreviates the unit of measure
for the primary scale in all upper case letters (i.e.:
MPH or KM/H), followed by the unit of measure for
the secondary scale in all lower case letters (i.e.: mph
or km/h). The speedometer graphics are white (pri-
mary scale) and red (secondary scale) against a black
field, making them clearly visible within the instru-
ment cluster in daylight. When illuminated from
behind by the panel lamps dimmer controlled cluster
illumination lighting with the exterior lamps turned
On, the white graphics appear blue-green, while the
red graphics still appear red. The orange gauge nee-
dle is internally illuminated. Gauge illumination isprovided by replaceable incandescent bulb and bulb
holder units located on the instrument cluster elec-
tronic circuit board. The speedometer is serviced as a
unit with the instrument cluster.
OPERATION
The speedometer gives an indication to the vehicle
operator of the vehicle road speed. This gauge is con-
trolled by the instrument cluster circuit board based
upon the cluster programming and electronic mes-
sages received by the cluster from the Powertrain
Control Module (PCM) over the Chrysler Collision
Detection (CCD) data bus. The speedometer is an air
core magnetic unit that receives battery current on
the instrument cluster electronic circuit board
through the fused ignition switch output (st-run) cir-
cuit whenever the ignition switch is in the On or
Start positions. The cluster is programmed to move
the gauge needle back to the low end of the scale
after the ignition switch is turned to the Off position.
The instrument cluster circuitry controls the gauge
needle position and provides the following features:
²Message Failure- If the cluster fails to receive
a speedometer message, it will hold the gauge needle
at the last indication for about four seconds, or until
the ignition switch is turned to the Off position,
whichever occurs first. If a new speedometer message
is not received after about four seconds, the gauge
needle will return to the far left (low) end of the
scale.
²Actuator Test- Each time the cluster is put
through the actuator test, the gauge needle will be
swept to several calibration points on the gauge scale
in a prescribed sequence in order to confirm the func-
tionality of the gauge and the cluster control cir-
cuitry.
The PCM continually monitors the vehicle speed
sensor to determine the vehicle road speed, then
sends the proper vehicle speed messages to the
instrument cluster. For further diagnosis of the
speedometer or the instrument cluster circuitry that
controls the gauge, (Refer to 8 - ELECTRICAL/IN-
STRUMENT CLUSTER - DIAGNOSIS AND TEST-
ING). For proper diagnosis of the vehicle speed
sensor, the PCM, the CCD data bus, or the message
inputs to the instrument cluster that control the
speedometer, a DRBIIItscan tool is required. Refer
to the appropriate diagnostic information.
TACHOMETER
DESCRIPTION
A tachometer is standard equipment on all instru-
ment clusters. The tachometer is located just to the
left of the speedometer near the center of the instru-
8J - 30 INSTRUMENT CLUSTERBR/BE
SHIFT INDICATOR (TRANSFER CASE) (Continued)

ment cluster. The tachometer consists of a movable
gauge needle or pointer controlled by the instrument
cluster circuitry and a fixed 210 degree scale on the
gauge dial face that reads left-to-right either from 0
to 6 for gasoline engines, or from 0 to 4 for diesel
engines. The text ªRPM X 1000º imprinted on the
cluster overlay directly below the hub of the tachom-
eter needle identifies that each number on the
tachometer scale is to be multiplied times 1000 rpm.
The gauge scale of the gasoline engine tachometer is
red lined at 5000 rpm, while the diesel engine
tachometer is red lined at 3375 rpm. The diesel
engine tachometer also includes text that specifies
ªDIESEL FUEL ONLYº located just above the hub of
the tachometer needle. The tachometer graphics are
white and red against a black field, making them
clearly visible within the instrument cluster in day-
light. When illuminated from behind by the panel
lamps dimmer controlled cluster illumination lighting
with the exterior lamps turned On, the white graph-
ics appear blue-green, while the red graphics still
appear red. The orange gauge needle is internally
illuminated. Gauge illumination is provided by
replaceable incandescent bulb and bulb holder units
located on the instrument cluster electronic circuit
board. The tachometer is serviced as a unit with the
instrument cluster.
OPERATION
The tachometer gives an indication to the vehicle
operator of the engine speed. This gauge is controlled
by the instrument cluster circuit board based upon
the cluster programming and electronic messages
received by the cluster from the Powertrain Control
Module (PCM) over the Chrysler Collision Detection
(CCD) data bus. The tachometer is an air core mag-
netic unit that receives battery current on the instru-
ment cluster electronic circuit board through the
fused ignition switch output (st-run) circuit whenever
the ignition switch is in the On or Start positions.
The cluster is programmed to move the gauge needle
back to the low end of the scale after the ignition
switch is turned to the Off position. The instrument
cluster circuitry controls the gauge needle position
and provides the following features:
²Message Failure- If the cluster fails to receive
an engine speed message, it will hold the gauge nee-
dle at the last indication for about four seconds, or
until the ignition switch is turned to the Off position,
whichever occurs first. If a new engine speed mes-
sage is not received after about four seconds, the
gauge needle will return to the far left (low) end of
the scale.
²Actuator Test- Each time the cluster is put
through the actuator test, the gauge needle will be
swept to several calibration points on the gauge scalein a prescribed sequence in order to confirm the func-
tionality of the gauge and the cluster control cir-
cuitry.
The PCM continually monitors the crankshaft posi-
tion sensor to determine the engine speed, then
sends the proper engine speed messages to the
instrument cluster. For further diagnosis of the
tachometer or the instrument cluster circuitry that
controls the gauge, (Refer to 8 - ELECTRICAL/IN-
STRUMENT CLUSTER - DIAGNOSIS AND TEST-
ING). For proper diagnosis of the crankshaft position
sensor, the PCM, the CCD data bus, or the message
inputs to the instrument cluster that control the
tachometer, a DRBIIItscan tool is required. Refer to
the appropriate diagnostic information.
TRANSMISSION OVERTEMP
INDICATOR
DESCRIPTION
A transmission over-temperature indicator lamp is
standard equipment on all instrument clusters. How-
ever, on vehicles not equipped with the optional auto-
matic transmission, this indicator is electronically
disabled. The transmission over-temperature indica-
tor is located near the lower edge of the instrument
cluster overlay, to the left of center. The transmission
over-temperature indicator consists of a stencilled
cutout of the words ªTRANS TEMPº in the opaque
layer of the instrument cluster overlay. The dark
outer layer of the overlay prevents the indicator from
being clearly visible when it is not illuminated. A red
lens behind the cutout in the opaque layer of the
overlay causes the ªTRANS TEMPº text to appear in
red through the translucent outer layer of the over-
lay when the indicator is illuminated from behind by
a Light Emitting Diode (LED) soldered onto the
instrument cluster electronic circuit board. The
transmission over-temperature indicator is serviced
as a unit with the instrument cluster.
OPERATION
The transmission over-temperature indicator gives
an indication to the vehicle operator when the trans-
mission fluid temperature is excessive, which may
lead to accelerated transmission component wear or
failure. This indicator is controlled by a transistor on
the instrument cluster circuit board based upon the
cluster programming and electronic messages
received by the cluster from the Powertrain Control
Module (PCM) over the Chrysler Collision Detection
(CCD) data bus. The transmission over-temperature
indicator Light Emitting Diode (LED) receives bat-
tery current on the instrument cluster electronic cir-
cuit board through the fused ignition switch output
BR/BEINSTRUMENT CLUSTER 8J - 31
TACHOMETER (Continued)

problems are found, the following procedure will help
locate a short or open in the left or right turn signal
indicator circuit. Refer to the appropriate wiring
information. The wiring information includes wiring
diagrams, proper wire and connector repair proce-
dures, details of wire harness routing and retention,
connector pin-out information and location views for
the various wire harness connectors, splices and
grounds.
(1) Disconnect and isolate the battery negative
cable. Remove the instrument cluster.
(2) Connect the battery negative cable. Activate
the hazard warning system by moving the hazard
warning switch button to the On position. Check for
battery voltage at the inoperative (right or left) turn
signal circuit cavity of the instrument panel wire
harness connector (Connector C2) for the instrument
cluster. There should be a switching (on and off) bat-
tery voltage signal. If OK, replace the faulty turn sig-
nal indicator bulb. If not OK, repair the open (right
or left) turn signal circuit to the left multi-function
switch as required.
UPSHIFT INDICATOR
DESCRIPTION
An upshift indicator is standard equipment on all
instrument clusters. However, on vehicles not
equipped with a manual transmission, this indicator
is disabled. The upshift indicator is located near the
fuel gauge in the instrument cluster overlay, to the
left of center. The upshift indicator consists of an
upward pointed arrow icon that is a stenciled cutout
in the opaque layer of the instrument cluster overlay.
The dark outer layer of the overlay prevents the indi-
cator from being clearly visible when it is not illumi-
nated. An amber lens behind the cutout in the
opaque layer of the overlay causes the icon to appear
in amber through the translucent outer layer of the
overlay when the indicator is illuminated from
behind by a replaceable incandescent bulb and bulb
holder unit located on the instrument cluster elec-
tronic circuit board. The upshift indicator is serviced
as a unit with the instrument cluster.
OPERATION
The upshift indicator gives an indication to the
vehicle operator when the transmission should be
shifted to the next highest gear in order to achieve
the best fuel economy. This indicator is controlled by
a transistor on the instrument cluster circuit board
based upon the cluster programming and electronic
messages received by the cluster from the Powertrain
Control Module (PCM) over the Chrysler Collision
Detection (CCD) data bus. The upshift indicator bulbreceives battery current on the instrument cluster
electronic circuit board through the fused ignition
switch output (st-run) circuit whenever the ignition
switch is in the On or Start positions; therefore, the
lamp will always be off when the ignition switch is in
any position except On or Start. The bulb only illu-
minates when it is provided a path to ground by the
instrument cluster transistor. On models not
equipped with a manual transmission, the incandes-
cent bulb and bulb holder unit are not installed at
the factory when the vehicle is built. The instrument
cluster will turn on the upshift indicator for the fol-
lowing reasons:
²Upshift Lamp-On Message- Each time the
cluster receives an upshift lamp-on message from the
PCM indicating the engine speed and load conditions
are right for a transmission upshift to occur, the
upshift indicator is illuminated. The indicator
remains illuminated until the cluster receives an
upshift lamp-off message from the PCM or until the
ignition switch is turned to the Off position, which-
ever occurs first. The PCM will normally send an
upshift lamp-off message three to five seconds after a
lamp-on message, if an upshift is not performed. The
indicator will then remain off until the vehicle stops
accelerating and is brought back into the range of
indicator operation, or until the transmission is
shifted into another gear.
²Actuator Test- Each time the cluster is put
through the actuator test, the indicator will be
turned on during the bulb check portion of the test to
confirm the functionality of the indicator and the
cluster control circuitry.
The PCM continually monitors the engine speed
and load conditions to determine the proper fuel and
ignition requirements. The PCM then sends the
proper messages to the instrument cluster. If the
upshift indicator fails to light during normal vehicle
operation, replace the bulb with a known good unit.
For further diagnosis of the upshift indicator or the
instrument cluster circuitry that controls the indica-
tor, (Refer to 8 - ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING). For
proper diagnosis of the PCM, the CCD data bus, or
the message inputs to the instrument cluster that
control the upshift indicator, a DRBIIItscan tool is
required. Refer to the appropriate diagnostic infor-
mation.
VOLTAGE GAUGE
DESCRIPTION
A voltage gauge is standard equipment on all
instrument clusters. The voltage gauge is located in
the upper left quadrant of the instrument cluster,
BR/BEINSTRUMENT CLUSTER 8J - 33
TURN SIGNAL INDICATORS (Continued)

above the temperature gauge. The voltage gauge con-
sists of a movable gauge needle or pointer controlled
by the instrument cluster circuitry and a fixed 90
degree scale on the cluster overlay that reads left-to-
right from 8 volts to 18 volts. An International Con-
trol and Display Symbol icon for ªBattery Charging
Conditionº is located directly below the lowest grad-
uation of the gauge scale. The voltage gauge graphics
are white against a black field except for a single red
graduation at each end of the gauge scale, making
them clearly visible within the instrument cluster in
daylight. When illuminated from behind by the panel
lamps dimmer controlled cluster illumination lighting
with the exterior lamps turned On, the white graph-
ics appear blue-green and the red graphics appear
red. The orange gauge needle is internally illumi-
nated. Gauge illumination is provided by replaceable
incandescent bulb and bulb holder units located on
the instrument cluster electronic circuit board. The
voltage gauge is serviced as a unit with the instru-
ment cluster.
OPERATION
The voltage gauge gives an indication to the vehi-
cle operator of the electrical system voltage. This
gauge is controlled by the instrument cluster circuit
board based upon the cluster programming and elec-
tronic messages received by the cluster from the
Powertrain Control Module (PCM) over the Chrysler
Collision Detection (CCD) data bus. The voltage
gauge is an air core magnetic unit that receives bat-
tery current on the instrument cluster electronic cir-
cuit board through the fused ignition switch output
(st-run) circuit whenever the ignition switch is in the
On or Start positions. The cluster is programmed to
move the gauge needle back to the low end of the
scale after the ignition switch is turned to the Off
position. The instrument cluster circuitry controls
the gauge needle position and provides the following
features:
²Charge Fail Message- Each time the cluster
receives a message from the PCM indicating a charge
fail condition (system voltage is 10.8 volts or lower),
the gauge needle is moved to the 8 volt graduation
on the gauge scale and the check gauges indicator is
illuminated. The gauge needle remains on the 8 volt
graduation and the check gauges indicator remains
illuminated until the cluster receives a message from
the PCM indicating there is no charge fail condition
(system voltage is 10.9 volts or higher, but lower
than 16.7 volts), or until the ignition switch is turned
to the Off position, whichever occurs first. On models
equipped with the optional diesel engine, the instru-
ment cluster is programmed to support the voltmeter
gauge needle above the low end of normal graduation
and suppress the check gauges indicator operationuntil ten seconds after the engine intake manifold air
heater has completed its cycle.
²Voltage High Message- Each time the cluster
receives a message from the PCM indicating a volt-
age high condition (system voltage is 16.7 volts or
higher), the gauge needle is moved to the 18 volt
graduation on the gauge scale and the check gauges
indicator is illuminated. The gauge needle remains
on the 18 volt graduation and the check gauges indi-
cator remains illuminated until the cluster receives a
message from the PCM indicating there is no voltage
high condition (system voltage is 16.6 volts or lower,
but higher than 10.9 volts), or until the ignition
switch is turned to the Off position, whichever occurs
first.
²Message Failure- If the cluster fails to receive
a system voltage message, it will hold the gauge nee-
dle at the last indication until a new message is
received, or until the ignition switch is turned to the
Off position, whichever occurs first.
²Actuator Test- Each time the cluster is put
through the actuator test, the gauge needle will be
swept to several calibration points on the gauge scale
in a prescribed sequence in order to confirm the func-
tionality of the gauge and the cluster control cir-
cuitry.
The PCM continually monitors the system voltage
to control the generator output. The PCM then sends
the proper system voltage messages to the instru-
ment cluster. For further diagnosis of the voltage
gauge or the instrument cluster circuitry that con-
trols the gauge, (Refer to 8 - ELECTRICAL/INSTRU-
MENT CLUSTER - DIAGNOSIS AND TESTING). If
the instrument cluster turns on the check gauges
indicator due to a charge fail or voltage high condi-
tion, it may indicate that the charging system
requires service. For proper diagnosis of the charging
system, the CCD data bus, or the message inputs to
the instrument cluster that control the voltage
gauge, a DRBIIItscan tool is required. Refer to the
appropriate diagnostic information.
WAIT-TO-START INDICATOR
DESCRIPTION
A wait-to-start indicator is standard equipment on
all instrument clusters, but is only functional in vehi-
cles equipped with an optional diesel engine. The
wait-to-start indicator is located near the lower edge
of the instrument cluster overlay, to the right of cen-
ter. The wait-to-start indicator consists of a stenciled
cutout of the text ªWAIT TO STARTº in the opaque
layer of the cluster overlay. The dark outer layer of
the overlay prevents the indicator from being clearly
visible when it is not illuminated. A red lens located
8J - 34 INSTRUMENT CLUSTERBR/BE
VOLTAGE GAUGE (Continued)

behind the cutout causes the ªWAIT TO STARTº text
to appear in red through the translucent outer layer
of the overlay when the indicator is illuminated from
behind by a Light Emitting Diode (LED) that is sol-
dered onto the instrument cluster electronic circuit
board. The wait-to-start indicator is serviced as a
unit with the instrument cluster.
OPERATION
The wait-to-start indicator gives an indication to
the vehicle operator when the diesel engine intake
air heater is energized in its preheat operating mode.
This indicator is controlled by a hard wired input to
the instrument cluster from the Engine Control Mod-
ule (ECM). The wait-to-start indicator Light Emitting
Diode (LED) receives battery current on the instru-
ment cluster electronic circuit board through the
fused ignition switch output (st-run) circuit whenever
the ignition switch is in the On or Start positions;
therefore, the lamp will always be off when the igni-
tion switch is in any position except On or Start. The
indicator LED only illuminates when it is switched to
ground by the input from the ECM. The ECM will
turn on the wait-to-start indicator by pulling the
wait-to-start indicator driver circuit to ground each
time the ignition switch is turned to the On or Start
positions. The indicator then remains illuminated
until the ECM detects that the air within the intake
manifold is the proper temperature to ensure reliable
and efficient engine starting, until the ECM detects
that the engine is running, or until the ignition
switch is turned to the Off position, whichever occurs
first.
The ECM continually monitors the intake manifold
air temperature sensor, the Manifold Absolute Pres-
sure (MAP) sensor, and many other vehicle condi-
tions to determine when the wait-to-start indicator
should be illuminated. For proper diagnosis of the
wait-to-start indicator, the ECM, or the inputs the
ECM uses to control the wait-to-start indicator oper-
ation, a DRBIIItscan tool is required. Refer to the
appropriate diagnostic information.
WASHER FLUID INDICATOR
DESCRIPTION
A washer fluid indicator is standard equipment on
all instrument clusters. The washer fluid indicator is
located near the lower edge of the instrument cluster
overlay, to the right of center. The washer fluid indi-
cator consists of a stenciled cutout of the words
ªLOW WASHERº in the opaque layer of the instru-
ment cluster overlay. The dark outer layer of the
overlay prevents the indicator from being clearly vis-
ible when it is not illuminated. An amber lens behindthe cutout in the opaque layer of the overlay causes
the ªLOW WASHERº text to appear in amber
through the translucent outer layer of the overlay
when it is illuminated from behind by a Light Emit-
ting Diode (LED) soldered onto the instrument clus-
ter electronic circuit board. The washer fluid
indicator is serviced as a unit with the instrument
cluster.
OPERATION
The washer fluid indicator gives an indication to
the vehicle operator when the fluid level in the
washer fluid reservoir is low. This indicator is con-
trolled by a transistor on the instrument cluster elec-
tronic circuit board based upon cluster programming
and a hard wired washer fluid level switch input to
the cluster. The washer fluid indicator Light Emit-
ting Diode (LED) receives battery current on the
instrument cluster electronic circuit board through
the fused ignition switch output (st-run) circuit
whenever the ignition switch is in the On or Start
positions; therefore, the indicator will always be off
when the ignition switch is in any position except On
or Start. The LED only illuminates when it is pro-
vided a path to ground by the instrument cluster
transistor. The instrument cluster will turn on the
washer fluid indicator for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the indicator is illuminated
for about two seconds as a bulb test.
²Washer Fluid Level Switch Input- Immedi-
ately after the bulb test, if the cluster senses ground
on the washer fluid switch sense circuit for more
than about thirty seconds, it turns on the washer
fluid indicator. Any time after the bulb test, the clus-
ter must sense ground on the washer fluid switch
sense circuit for more than about sixty seconds before
it turns on the indicator. Once illuminated, the indi-
cator will remain illuminated until the ignition
switch is cycled and the cluster senses an open cir-
cuit on the low washer fluid sense input. This strat-
egy is intended to reduce the effect that fluid
sloshing within the washer reservoir can have on
reliable indicator operation.
²Actuator Test- Each time the cluster is put
through the actuator test, the indicator will be
turned on during the bulb check portion of the test to
confirm the functionality of the LED and the cluster
control circuitry.
The washer fluid level switch is connected in series
between ground and the washer fluid switch sense
input to the instrument cluster. For more informa-
tion on the washer fluid level switch,(Refer to 8 -
ELECTRICAL/WIPERS/WASHERS/WASHER FLUID
LEVEL SWITCH - OPERATION). For further diag-
nosis of the washer fluid indicator or the instrument
BR/BEINSTRUMENT CLUSTER 8J - 35
WAIT-TO-START INDICATOR (Continued)

OPERATION
The water-in-fuel indicator gives an indication to
the vehicle operator when the water accumulated in
the diesel engine fuel filter/separator filter bowl
requires draining. This indicator is controlled by a
transistor on the instrument cluster circuit board
based upon cluster programming and electronic mes-
sages received by the cluster from the Engine Control
Module (ECM) over the Chrysler Collision Detection
(CCD) data bus. The water-in-fuel indicator Light
Emitting Diode (LED) receives battery current on the
instrument cluster electronic circuit board through
the fused ignition switch output (st-run) circuit
whenever the ignition switch is in the On or Start
positions; therefore, the indicator will always be off
when the ignition switch is in any position except On
or Start. The LED only illuminates when it is
switched to ground by the instrument cluster transis-
tor. The instrument cluster will turn on the water-in-
fuel indicator for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the indicator is illuminated
for about two seconds as a bulb test.
²Water-In-Fuel Lamp-On Message- Each time
the cluster receives a water-in-fuel lamp-on messagefrom the ECM, the indicator will be illuminated. The
indicator remains illuminated until the cluster
receives a water-in-fuel lamp-off message from the
ECM or until the ignition switch is turned to the Off
position, whichever occurs first.
²Actuator Test- Each time the cluster is put
through the actuator test, the indicator will be
turned on during the bulb check portion of the test to
confirm the functionality of the LED and the cluster
control circuitry.
The ECM continually monitors the water-in-fuel
sensor, then sends the proper messages to the instru-
ment cluster. For further diagnosis of the water-in-
fuel indicator or the instrument cluster circuitry that
controls the indicator, (Refer to 8 - ELECTRICAL/IN-
STRUMENT CLUSTER - DIAGNOSIS AND TEST-
ING). For proper diagnosis of the water-in-fuel
sensor, the ECM, the CCD data bus, or the message
inputs to the instrument cluster that control the
water-in-fuel indicator, a DRBIIItscan tool is
required. Refer to the appropriate diagnostic
information.
BR/BEINSTRUMENT CLUSTER 8J - 37
WATER-IN-FUEL INDICATOR (Continued)

MARKER LAMP
REMOVAL..............................22
INSTALLATION...........................23
MULTI-FUNCTION SWITCH
DESCRIPTION...........................23
OPERATION.............................24
DIAGNOSIS AND TESTING.................25
MULTI-FUNCTION SWITCH...............25
REMOVAL..............................27
INSTALLATION...........................28
OUTBOARD IDENTIFICATION LAMP
REMOVAL..............................28
INSTALLATION...........................29
PARK/TURN SIGNAL LAMP
REMOVAL..............................29
INSTALLATION...........................29
PARK/TURN SIGNAL LAMP UNIT
REMOVAL..............................29INSTALLATION...........................29
TAIL LAMP
DESCRIPTION...........................29
OPERATION.............................29
REMOVAL..............................29
INSTALLATION...........................30
TAIL LAMP UNIT
REMOVAL..............................30
INSTALLATION...........................30
TURN SIGNAL CANCEL CAM
DESCRIPTION...........................30
OPERATION.............................31
UNDERHOOD LAMP
REMOVAL..............................31
INSTALLATION...........................32
UNDERHOOD LAMP UNIT
REMOVAL..............................32
INSTALLATION...........................32
LAMPS/LIGHTING - EXTERIOR
DESCRIPTION - TURN SIGNAL & HAZARD
WARNING SYSTEM
A turn signal and hazard warning system is stan-
dard factory-installed safety equipment on this
model. The turn signal and hazard warning system
includes the following major components, which are
described in further detail elsewhere in this service
information:
²Combination Flasher- The electronic combi-
nation flasher is installed in the Junction Block (JB),
which is located behind the fuse access panel on the
left outboard end of the instrument panel.
²Hazard Warning Switch- The hazard warning
switch is integral to the multi-function switch on the
left side of the steering column. The hazard warning
switch button protrudes from a dedicated opening in
the shroud on the top of the steering column, just
below the steering wheel.
²Turn Signal Cancel Cam- The turn signal
cancel cam is integral to the clockspring, which is
located beneath the steering column shrouds at the
top of the steering column, just below the steering
wheel.
²Turn Signal Indicators- The two turn signal
indicators, one right and one left, are integral to the
ElectroMechanical Instrument Cluster (EMIC)
located in the instrument panel.
²Turn Signal Lamps- The front turn signal
lamps are integral to the lower front outboard ends
of the headlamp modules, located just outboard of the
two sides of the radiator grille opening. The rear
turn signal lamps are integral to the taillamp mod-
ules located on either side of the vehicle. For pickup
models the taillamp modules are secured to the rear
of the quarter panels at each side of the tailgate
opening. For cab and chassis models the taillampmodules are secured by a stamped steel bracket on
the outboard side of each frame rail near the rear of
the vehicle.
²Turn Signal Switch- The turn signal switch is
integral to the multi-function switch on the left side
of the steering column. The multi-function switch
control stalk that actuates the turn signal switch
protrudes from a dedicated opening in the steering
column shrouds on the left side of the column, just
below the steering wheel.
Hard wired circuitry connects the turn signal and
hazard warning system components to each other
through the electrical system of the vehicle. These
hard wired circuits are integral to several wire har-
nesses, which are routed throughout the vehicle and
retained by many different methods. These circuits
may be connected to each other, to the vehicle elec-
trical system and to the turn signal and hazard
warning system components through the use of a
combination of soldered splices, splice block connec-
tors and many different types of wire harness termi-
nal connectors and insulators. Refer to the
appropriate wiring information. The wiring informa-
tion includes wiring diagrams, proper wire and con-
nector repair procedures, details of wire harness
routing and retention, connector pin-out information
and location views for the various wire harness con-
nectors, splices and grounds.
OPERATION - TURN SIGNAL & HAZARD
WARNING SYSTEM
The turn signal system operates on battery current
received on a fused ignition switch output (run-acc)
circuit so that the turn signals will only operate with
the ignition switch in the On or Accessory positions.
The hazard warning system operates on non-
switched battery current received on a fused B(+) cir-
cuit so that the hazard warning remains operational
8L - 2 LAMPS/LIGHTING - EXTERIORBR/BE

regardless of the ignition switch position. When the
turn signal (multi-function) switch control stalk is
moved up (right turn) or down (left turn), the turn
signal system is activated. When the turn signal sys-
tem is activated, the circuitry of the turn signal
switch and the combination flasher will cause the
selected (right or left) turn signal indicator, front
park/turn signal lamp, and rear tail/stop/turn signal
lamp to flash on and off. With the hazard warning
(multi-function) switch in the On position, the hazard
warning system is activated. When the hazard warn-
ing system is activated, the circuitry of the hazard
warning switch and the combination flasher will
cause both the right side and the left side turn signal
indicators, front park/turn signal lamps, and rear
tail/stop/turn signal lamps to flash on and off.
Refer to the owner's manual in the vehicle glove
box for more information on the features, use and
operation of the turn signal and hazard warning sys-
tem.
DIAGNOSIS AND TESTING - TURN SIGNAL &
HAZARD WARNING SYSTEM
When diagnosing the turn signal and hazard warn-
ing circuits, remember that high generator output
can burn out bulbs rapidly and repeatedly. If this is a
problem on the vehicle being diagnosed, be certain to
diagnose and repair the charging system as required.
If the problem being diagnosed is related to a failure
of the turn signals to automatically cancel following
completion of a turn, inspect the multi-function
switch for a faulty or damaged cancel actuator and
inspect the turn signal cancel cam on the clockspring
for damaged lobes or improper installation. Refer to
the appropriate wiring information. The wiring infor-
mation includes wiring diagrams, proper wire and
connector repair procedures, details of wire harness
routing and retention, connector pin-out information
and location views for the various wire harness con-
nectors, splices and grounds.
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.(1) Turn the ignition switch to the On position.
Actuate the turn signal switch or the hazard warning
switch. Observe the turn signal indicator lamp(s) in
the instrument cluster. If the flash rate is very high,
check for a turn signal bulb that is not lit or is very
dimly lit. Repair the circuits to that lamp or replace
the faulty bulb, as required. If the turn signal indi-
cator(s) fail to light, go to Step 2.
(2) Turn the ignition switch to the Off position.
Check the fused ignition switch output (run-acc) fuse
(Fuse 10 - 10 ampere) in the Junction Block (JB) and
the fused B(+) fuse (Fuse4-20ampere) in the
Power Distribution Center (PDC). If OK, go to Step
3. If not OK, repair the shorted circuit or component
as required and replace the faulty fuse(s).
(3) Check for battery voltage at the fused B(+) fuse
(Fuse4-20ampere) in the PDC. If OK, go to Step 4.
If not OK, repair the open fused B(+) circuit between
the PDC and the battery as required.
(4) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (run-acc) fuse (Fuse 10 - 10 ampere) in the
JB. If OK, go to Step 5. If not OK, repair the open
fused ignition switch output (run-acc) circuit between
the JB and the ignition switch as required.
(5) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Remove the combination flasher from the JB and
replace it with a known good unit. Reconnect the bat-
tery negative cable. Test the operation of the turn
signal and hazard warning systems. If OK, discard
the faulty combination flasher. If not OK, remove the
test flasher and go to Step 6.
(6) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (run-acc) circuit cavity in the JB receptacle
for the combination flasher. If OK, go to Step 7. If
not OK, repair the open fused ignition switch output
(run-acc) circuit between the combination flasher and
the fused ignition switch output (run-acc) fuse (Fuse
10 - 10 ampere) in the JB as required.
(7) Turn the ignition switch to the Off position.
Check for battery voltage at the fused B(+) circuit
cavity of the JB receptacle for the combination
flasher. If OK, go to Step 8. If not OK, repair the
open fused B(+) circuit between the combination
flasher and the fused B(+) fuse (Fuse4-20ampere)
in the PDC as required.
(8) Disconnect and isolate the battery negative
cable. Check for continuity between the ground cir-
cuit cavity of the JB receptacle for the combination
flasher and a good ground. There should be continu-
ity. If OK, go to Step 9. If not OK, repair the open
ground circuit to ground (G201) as required.
BR/BELAMPS/LIGHTING - EXTERIOR 8L - 3
LAMPS/LIGHTING - EXTERIOR (Continued)

COMBINATION FLASHER
DESCRIPTION
The combination flasher is located in the Junction
Block (JB) behind the fuse access panel on the left
outboard end of the instrument panel. The combina-
tion flasher is a smart relay that functions as both
the turn signal system and the hazard warning sys-
tem flasher. The combination flasher contains active
electronic Integrated Circuitry (IC) elements. This
flasher is designed to handle the current flow
requirements of the factory-installed lighting. If sup-
plemental lighting is added to the turn signal lamp
circuits, such as when towing a trailer with lights,
the combination flasher will automatically try to
compensate to keep the flash rate the same.
The combination flasher has five blade-type termi-
nals that connect it to the vehicle electrical system
through five matching cavities in the receptacle of
the JB. While the combination flasher has a Interna-
tional Standards Organization (ISO)-type relay ter-
minal configuration or footprint, the internal
circuitry is much different. The combination flasher
does not use standard ISO-relay inputs or provide
ISO-relay type outputs or functions. The combination
flasher should never be substituted for an ISO-relay
or replaced with an ISO-relay, or else component and
vehicle damage may occur.
The combination flasher cannot be repaired or
adjusted and, if faulty or damaged, it must be
replaced.
OPERATION
The combination flasher has five blade-type termi-
nals intended for the following inputs and outputs:
fused B(+), fused ignition switch output, ground, turn
signal circuit, and hazard warning circuit. Constant
battery voltage and ground are supplied to the
flasher so that it can perform the hazard warning
function, and ignition switched battery voltage is
supplied for the turn signal function.
The Integrated Circuitry (IC) within the combina-
tion flasher (Fig. 6) contains the logic that controls
the flasher operation and the flash rate. Pin 6 of the
IC receives a sense voltage from the hazard warning
circuit of the multi-function switch. When the hazard
warning switch is turned on, the9hazard on sense9
voltage will become low due to the circuit being
grounded through the turn signal bulbs. This low
voltage sense signals the IC to energize the flash con-
trol Positive-Negative-Positive (PNP) transistor at a
pre-calibrated flash rate or frequency. Each time the
PNP transistor energizes the hazard warning circuit,
the pin 69hazard on sense9voltage will become high
and the IC signals the PNP transistor to de-energize
the circuit. This cycling will continue until the haz-
ard warning switch is turned off.
Likewise, pin 8 of the IC receives a sense voltage
from the turn signal circuits of the multi-function
switch. When the left or right turn signal switch is
turned on, the9turn signal on sense9voltage will
become low due to the circuit being grounded
through the turn signal bulbs. This low voltage sense
signals the IC to energize the flash control PNP tran-
sistor at a pre-calibrated flash rate or frequency.
Each time the PNP transistor energizes the turn sig-
nal circuit, the pin 89turn signal on sense9voltage
Fig. 5 Roof Clearance Lamps
1 - ROOF
2 - LAMP LENS
3 - BULB
4 - SOCKET
Fig. 6 Combination Flasher - Typical
BR/BELAMPS/LIGHTING - EXTERIOR 8L - 7
CLEARANCE LAMP (Continued)

will become high and the IC signals the PNP transis-
tor to de-energize the circuit. This cycling will con-
tinue until the right or left turn signal switch is
turned off.
A special design feature of the combination flasher
allows it to9sense9that a turn signal circuit or bulb
is not operating, and provide the driver an indication
of the condition by flashing the remaining bulbs in
the affected circuit at a higher rate (120 flashes-per-
minute or higher). Conventional flashers either con-
tinue flashing at their typical rate (heavy-duty type),
or discontinue flashing the affected circuit entirely
(standard-duty type). During turn signal operation,
the combination flasher IC compares normal battery
voltage input on pin 2 with the shunt resistor voltage
input on pin 7. If the IC9senses9that the voltage dif-
ference between pin 2 and pin 7 is different than the
pre-calibrated value of the IC, it will increase the
rate at which it signals the PNP transistor to ener-
gize the pin 1 output. Thus, the inoperative half (left
or right side) of the turn signal circuit will flash
faster.
Because of the active electronic elements within
the combination flasher, it cannot be tested with con-
ventional automotive electrical test equipment. If the
combination flasher is believed to be faulty, test the
turn signal system and hazard warning system. Then
replace the combination flasher with a known good
unit to confirm system operation. (Refer to 8 - ELEC-
TRICAL/LAMPS/LIGHTING - EXTERIOR/TURN
SIGNAL & HAZARD WARNING SYSTEM - DIAG-
NOSIS AND TESTING).
REMOVAL
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.
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the fuse access panel by unsnapping it
from the left outboard end of the instrument panel.
(3) Remove the combination flasher from the Junc-
tion Block (JB) (Fig. 7).
INSTALLATION
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.
(1) Position the combination flasher in the proper
receptacle of the Junction Block (JB).
(2) Align the terminals of the combination flasher
with the terminal cavities in the JB receptacle for
the flasher.
(3) Push in firmly and evenly on the combination
flasher until the terminals are fully seated in the ter-
minal cavities of the JB receptacle for the flasher.
(4) Reinstall the fuse access panel by snapping it
onto the left outboard end of the instrument panel.
(5) Reconnect the battery negative cable.
Fig. 7 Junction Block
1 - JUNCTION BLOCK
2 - FUSE ACCESS PANEL
8L - 8 LAMPS/LIGHTING - EXTERIORBR/BE
COMBINATION FLASHER (Continued)