2001 DODGE RAM ECU

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 instrument cluster to the instru-
ment panel.
(2) If the vehicle is equipped with an automatic
transmission, position the gear selector indicator onto
the back of the cluster housing (Fig. 3).
(3) If the vehicle is equipped with an automatic
transmission, install and tighten the two screws that
secure the gear selector indicator mechanism to the
back of the cluster housing. Tighten the screws to 2.2
N´m (20 in. lbs.).
(4) Align the instrument cluster with the cluster
opening in the instrument panel and push the cluster
firmly and evenly into place. The instrument panel
wire harness has two self-docking connectors that
will be automatically aligned with, and connected to
the instrument cluster connector receptacles when
the cluster is properly installed in the instrument
panel.
(5) Install and tighten the four screws that secure
the instrument cluster to the instrument panel (Fig.
2). Tighten the screws to 2.2 N´m (20 in. lbs.).
(6) Reinstall the cluster bezel onto the instrument
panel. (Refer to 23 - BODY/INSTRUMENT PANEL/
CLUSTER BEZEL - INSTALLATION).
(7) If the vehicle is equipped with an automatic
transmission, confirm proper operation of the gear
selector indicator. Calibrate the indicator, if required.
(Refer to 19 - STEERING/COLUMN - INSTALLA-
TION).
(8) Reconnect the battery negative cable.
NOTE: Some of the indicators in this instrument
cluster are either programmable (upshift indicator)
or automatically configured (cruise, overdrive-off,
and transmission overtemp indicators) when the
cluster is connected to the vehicle electrical sys-
tem. This feature allows those indicator lamps to be
enabled or disabled for compatibility with certain
optional equipment. If a new instrument cluster is
being installed, use a DRBIIITscan tool to programthe instrument cluster with the proper vehicle
equipment option setting to enable and/or disable
the upshift indicator lamp. Refer to the appropriate
diagnostic information.
ABS INDICATOR
DESCRIPTION
An Antilock Brake System (ABS) indicator is stan-
dard equipment on all instrument clusters. This indi-
cator serves both the standard equipment Rear
Wheel Anti-Lock (RWAL) and optional equipment
4-Wheel Anti-Lock (4WAL) brake systems. The ABS
indicator is located near the lower edge of the instru-
ment cluster overlay, to the left of center. The ABS
indicator consists of a stencilled cutout of the Inter-
national Control and Display Symbol icon for ªFail-
ure of Anti-lock Braking Systemº 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. 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 it is
illuminated from behind by a Light Emitting Diode
(LED) soldered onto the instrument cluster electronic
circuit board. The ABS indicator is serviced as a unit
with the instrument cluster.
OPERATION
The ABS indicator gives an indication to the vehi-
cle operator when the ABS system is faulty or inop-
erative. This indicator is controlled by a transistor on
the instrument cluster circuit board based upon clus-
ter programming and electronic messages received by
the cluster from the Controller Antilock Brake (CAB)
over the Chrysler Collision Detection (CCD) data bus.
The ABS 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
LED will always be off when the ignition switch is in
any position except On or Start. The LED only illu-
minates when it is provided a path to ground by the
instrument cluster transistor. The instrument cluster
will turn on the ABS indicator for the following rea-
sons:
²Bulb Test- Each time the ignition switch is
turned to the On position the ABS indicator is illu-
minated by the cluster for about two seconds as a
bulb test.
²ABS Lamp-On Message- Each time the clus-
ter receives a lamp-on message from the CAB, the
8J - 14 INSTRUMENT CLUSTERBR/BE
INSTRUMENT CLUSTER (Continued)

ABS indicator will be illuminated. The indicator
remains illuminated until the cluster receives a
lamp-off message from the CAB, or until the ignition
switch is turned to the Off position, whichever occurs
first.
²Communication Error- If the cluster receives
no lamp-on or lamp-off messages from the CAB for
six consecutive seconds, the ABS indicator is illumi-
nated. The indicator remains illuminated until the
cluster receives a valid message from the CAB, or
until the ignition switch is turned to the Off position,
whichever occurs first.
²Actuator Test- Each time the instrument clus-
ter is put through the actuator test, the ABS indica-
tor will be turned on during the bulb check portion of
the test to confirm the functionality of the LED and
the cluster control circuitry.
²ABS Diagnostic Test- The ABS indicator is
blinked on and off by lamp-on and lamp-off messages
from the CAB during the performance of the ABS
diagnostic tests.
The CAB continually monitors the ABS circuits
and sensors to decide whether the system is in good
operating condition. The CAB then sends the proper
lamp-on or lamp-off messages to the instrument clus-
ter. If the CAB sends a lamp-on message after the
bulb test, it indicates that the CAB has detected a
system malfunction and/or that the ABS system has
become inoperative. The CAB will store a Diagnostic
Trouble Code (DTC) for any malfunction it detects.
Each time the ABS indicator fails to light due to an
open or short in the cluster ABS indicator circuit, the
cluster sends a message notifying the CAB of the
condition, and the CAB will store a DTC. For proper
diagnosis of the antilock brake system, the CAB, the
CCD data bus, or the message inputs to the instru-
ment cluster that control the ABS indicator, a
DRBIIItscan tool is required. Refer to the appropri-
ate diagnostic information.
AIRBAG INDICATOR
DESCRIPTION
An airbag indicator is standard equipment on all
instrument clusters. However, on vehicles not
equipped with airbags, this indicator is electronically
disabled. The airbag indicator is located near the
lower edge of the instrument cluster overlay, to the
right of center. The airbag indicator consists of a
stenciled cutout of the word ªAIRBAGº 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 ªAIRBAGº text to appear in redthrough 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 airbag indicator is
serviced as a unit with the instrument cluster.
OPERATION
The airbag indicator gives an indication to the
vehicle operator when the airbag system is faulty or
inoperative. The airbag 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 Airbag Control
Module (ACM) over the Chrysler Collision Detection
(CCD) data bus. The airbag 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 indicator will always be off when the
ignition switch is in any position except On or Start.
The LED only illuminates when it is provided a path
to ground by the instrument cluster transistor. The
instrument cluster will turn on the airbag indicator
for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the airbag indicator is illu-
minated for about seven seconds. The first two sec-
onds is the cluster bulb test function, and the
remainder is the ACM bulb test function.
²ACM Lamp-On Message- Each time the clus-
ter receives a lamp-on message from the ACM, the
airbag indicator will be illuminated. The indicator
remains illuminated for about twelve seconds or until
the cluster receives a lamp-off message from the
ACM, whichever is longer.
²Communication Error- If the cluster receives
no airbag messages for three consecutive seconds, the
airbag indicator is illuminated. The indicator
remains illuminated for about twelve seconds or until
the cluster receives a single lamp-off message from
the ACM, whichever is longer.
²Actuator Test- Each time the cluster is put
through the actuator test, the airbag 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 ACM continually monitors the airbag system
circuits and sensors to decide whether the system is
in good operating condition. The ACM then sends the
proper lamp-on or lamp-off messages to the instru-
ment cluster. If the ACM sends a lamp-on message
after the bulb test, it indicates that the ACM has
detected a system malfunction and/or that the air-
bags may not deploy when required, or may deploy
when not required. The ACM will store a Diagnostic
BR/BEINSTRUMENT CLUSTER 8J - 15
ABS INDICATOR (Continued)

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 engine coolant
temperature sensor to determine the engine operat-
ing temperature. The PCM then sends the proper
engine coolant temperature messages to the instru-
ment cluster. For further diagnosis of the engine cool-
ant temperature gauge or the instrument cluster
circuitry that controls the gauge, (Refer to 8 - ELEC-
TRICAL/INSTRUMENT CLUSTER - DIAGNOSIS
AND TESTING). If the instrument cluster turns on
the check gauges indicator due to a high engine tem-
perature gauge reading, it may indicate that the
engine or the engine cooling system requires service.
For proper diagnosis of the engine coolant tempera-
ture sensor, the PCM, the CCD data bus, or the mes-
sage inputs to the instrument cluster that control the
engine coolant temperature gauge, a DRBIIItscan
tool is required. Refer to the appropriate diagnostic
information.
FUEL GAUGE
DESCRIPTION
A fuel gauge is standard equipment on all instru-
ment clusters. The fuel gauge is located in the lower
right quadrant of the instrument cluster, below the
oil pressure gauge. The fuel gauge consists of a mov-
able gauge needle or pointer controlled by the instru-
ment cluster circuitry and a fixed 90 degree scale on
the cluster overlay that reads left-to-right from E (or
Empty) to F (or Full). An International Control and
Display Symbol icon for ªFuelº is located on the clus-
ter overlay, directly below the highest graduation of
the gauge scale. The text ªFUEL DOORº and an
arrowhead pointed to the left side of the vehicle is
imprinted on the cluster overlay directly below the
fuel gauge to provide the driver with a reminder as
to the location of the fuel filler access. The fuel gauge
graphics are white against a black field except for a
single red graduation at the low end of the gauge
scale, 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 and the
red graphics appear red. The orange gauge needle is
internally illuminated. Gauge illumination is pro-
vided by replaceable incandescent bulb and bulb
holder units located on the instrument cluster elec-
tronic circuit board. The fuel gauge is serviced as a
unit with the instrument cluster.
OPERATION
The fuel gauge gives an indication to the vehicle
operator of the level of fuel in the fuel tank. 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 fuel gauge is
an air core magnetic unit that receives battery cur-
rent 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. 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:
²Percent Tank Full Message- Each time the
cluster receives a message from the PCM indicating
the percent tank full, the cluster programming
applies an algorithm to calculate the proper gauge
needle position, then moves the gauge needle to the
proper position on the gauge scale. The algorithm is
used to dampen gauge needle movement against the
negative effect that fuel sloshing within the fuel tank
can have on accurate inputs from the fuel tank send-
ing unit to the PCM.
²Less Than 12.5 Percent Tank Full Message-
Each time the cluster receives messages from the
PCM indicating the percent tank full is 12.5 (one-
eighth) or less for 10 consecutive seconds and the
vehicle speed is zero, or for 60 consecutive seconds
and the vehicle speed is greater than zero, the gauge
needle is moved to the proper position on the gauge
scale, the low fuel indicator is illuminated, and a sin-
gle chime tone is sounded. The low fuel indicator
remains illuminated until the cluster receives mes-
sages from the PCM indicating that the percent tank
full is greater than 12.5 (one-eighth) for 10 consecu-
tive seconds and the vehicle speed is zero, or for 60
consecutive seconds and the vehicle speed is greater
than zero, or until the ignition switch is turned to
the Off position, whichever occurs first. The chime
tone feature will only repeat during the same igni-
tion cycle if the low fuel indicator is cycled off and
then on again by the appropriate percent tank full
messages from the PCM.
²Less Than Empty Percent Tank Full Mes-
sage- Each time the cluster receives a message from
the PCM indicating the percent tank full is less than
empty, the gauge needle is moved to the far left (low)
end of the gauge scale and the low fuel indicator is
illuminated immediately. This message would indi-
cate that the fuel tank sender input to the PCM is a
short circuit.
8J - 20 INSTRUMENT CLUSTERBR/BE
ENGINE TEMPERATURE GAUGE (Continued)

²More Than Full Percent Tank Full Message
- Each time the cluster receives a message from the
PCM indicating the percent tank full is more than
full, the gauge needle is moved to the far left (low)
end of the gauge scale and the low fuel indicator is
illuminated immediately. This message would indi-
cate that the fuel tank sender input to the PCM is an
open circuit.
²Message Failure- If the cluster fails to receive
a percent tank full message, it will hold the gauge
needle 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 fuel tank send-
ing unit, then sends the proper messages to the
instrument cluster. For further diagnosis of the fuel
gauge or the instrument cluster circuitry that con-
trols the gauge, (Refer to 8 - ELECTRICAL/INSTRU-
MENT CLUSTER - DIAGNOSIS AND TESTING).
For proper diagnosis of the fuel tank sending unit,
the PCM, the CCD data bus, or the message inputs
to the instrument cluster that control the fuel gauge,
a DRBIIItscan tool is required. Refer to the appro-
priate diagnostic information.
GEAR SELECTOR INDICATOR
DESCRIPTION
A mechanical automatic transmission gear selector
indicator is standard factory-installed equipment on
this model, when it is also equipped with an optional
automatic transmission. The gear selector indicator
consists of a molded black plastic housing with inte-
gral mounting tabs that is secured to the back of the
instrument cluster housing with two screws. A face
plate on the indicator housing is visible through a
rectangular cutout in the lower right corner of the
instrument cluster overlay, just below the fuel gauge.
Vehicles with a manual transmission have a block-off
plate mounted to the back of the instrument cluster
behind this cutout in the overlay, in place of the gear
selector indicator. Near the top of this face plate the
following characters are imprinted from left to right:
ªP,º ªR,º ªN,º ªD,º ª2,º and ª1.º Respectively, these
characters represent the park, reverse, neutral,
drive, second gear, and first gear positions of the
transmission gear selector lever on the steering col-
umn. Directly below each character on the face plateis a small, rectangular window, and behind these
windows is a single, movable red pointer.
The gear selector indicator graphics are white
against a black field except for the single red pointer,
making them clearly visible within the instrument
cluster in daylight. When illuminated from behind by
the panel lamps dimmer controlled cluster illumina-
tion lighting with the exterior lamps turned On, the
white graphics appear blue-green, while the red
pointer still appears red. Indicator illumination is
provided by replaceable incandescent bulb and bulb
holder units located on the instrument cluster elec-
tronic circuit board. The gear selector indicator is
available for service replacement separate from the
instrument cluster. The instrument cluster must be
removed from the instrument panel for service access
to the gear selector indicator. (Refer to 8 - ELECTRI-
CAL/INSTRUMENT CLUSTER - REMOVAL).
OPERATION
The mechanical gear selector indicator gives an
indication of the transmission gear that has been
selected with the automatic transmission gear selec-
tor lever. A red pointer appears in a window below
the character in the indicator representing the trans-
mission gear that has been selected. The small,
spring-loaded pointer moves on a track through a
trolley-like mechanism within the indicator housing.
A short length of small diameter stranded cable is
attached to one side of the pointer trolley and is
encased in a tubular plastic housing that exits the
right side of the indicator. The cable is routed
through the instrument panel and under the steering
column to the left side of the column. The looped end
of the cable is hooked over the end of the PRNDL
driver lever on the steering column gearshift mecha-
nism, and the cable housing is secured in a molded
plastic adjuster and bracket on the column housing.
When the gear selector lever is moved the PRNDL
driver lever moves, which moves the pointer through
the mechanical actuator cable. The cable adjuster
and bracket unit mounted on the steering column
housing provides a mechanical means of calibrating
the gear selector indicator mechanism. (Refer to 19 -
STEERING/COLUMN - INSTALLATION).
HIGH BEAM INDICATOR
DESCRIPTION
A high beam indicator is standard equipment on
all instrument clusters. The high beam indicator is
located near the upper edge of the instrument cluster
overlay, between the tachometer and the speedome-
ter. The high beam indicator consists of a stenciled
cutout of the International Control and Display Sym-
BR/BEINSTRUMENT CLUSTER 8J - 21
FUEL GAUGE (Continued)

ing wheel, then inspecting the headlamps at the
front of the vehicle. Once the headlamp low beams
are selected, turn the headlamp switch to the Off
position.
(2) Disconnect and isolate the battery negative
cable. Remove the instrument cluster from the
instrument panel. Check for continuity between the
high beam indicator driver circuit cavity of the
instrument panel wire harness connector (Connector
C2) for the instrument cluster and a good ground.
There should be no continuity. If OK, replace the
faulty instrument cluster. If not OK, repair the
shorted high beam indicator driver circuit between
the instrument cluster and the headlamp beam select
(multi-function) switch as required.
LOW FUEL INDICATOR
DESCRIPTION
A low fuel indicator is standard equipment on all
instrument clusters. The low fuel indicator is located
near the lower edge of the instrument cluster overlay,
to the right of center. The low fuel indicator consists
of a stenciled cutout of the International Control and
Display Symbol icon for ªFuelº 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. 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 Light Emit-
ting Diode (LED) soldered onto the instrument clus-
ter electronic circuit board. The low fuel indicator
lamp is serviced as a unit with the instrument clus-
ter.
OPERATION
The low fuel indicator gives an indication to the
vehicle operator when the level of fuel in the fuel
tank becomes low. 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 Powertrain
Control Module (PCM) over the Chrysler Collision
Detection (CCD) data bus. The low fuel indicator
Light Emitting Diode (LED) 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; therefore, the LED 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 clustertransistor. The instrument cluster will turn on the
low 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.
²Less Than 12.5 Percent Tank Full Message-
Each time the cluster receives messages from the
PCM indicating the percent tank full is 12.5 (one-
eighth) or less for 10 consecutive seconds and the
vehicle speed is zero, or for 60 consecutive seconds
and the vehicle speed is greater than zero, the low
fuel indicator is illuminated and a single chime tone
is sounded. The low fuel indicator remains illumi-
nated until the cluster receives messages from the
PCM indicating that the percent tank full is greater
than 12.5 (one-eighth) for 10 consecutive seconds and
the vehicle speed is zero, or for 60 consecutive sec-
onds and the vehicle speed is greater than zero, or
until the ignition switch is turned to the Off position,
whichever occurs first. The chime tone feature will
only repeat during the same ignition cycle if the low
fuel indicator is cycled off and then on again by the
appropriate percent tank full messages from the
PCM.
²Less Than Empty Percent Tank Full Mes-
sage- Each time the cluster receives a message from
the PCM indicating the percent tank full is less than
empty, the low fuel indicator is illuminated immedi-
ately. This message would indicate that the fuel tank
sender input to the PCM is a short circuit.
²More Than Full Percent Tank Full Message
- Each time the cluster receives a message from the
PCM indicating the percent tank full is more than
full, the low fuel indicator is illuminated immedi-
ately. This message would indicate that the fuel tank
sender input to the PCM is an open circuit.
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 PCM continually monitors the fuel tank send-
ing unit, then sends the proper messages to the
instrument cluster. For further diagnosis of the low
fuel indicator or the instrument cluster circuitry that
controls the LED, (Refer to 8 - ELECTRICAL/IN-
STRUMENT CLUSTER - DIAGNOSIS AND TEST-
ING). For proper diagnosis of the fuel tank sending
unit, the PCM, the CCD data bus, or the message
inputs to the instrument cluster that control the low
fuel indicator, a DRBIIItscan tool is required. Refer
to the appropriate diagnostic information.
BR/BEINSTRUMENT CLUSTER 8J - 23
HIGH BEAM INDICATOR (Continued)

MALFUNCTION INDICATOR
LAMP (MIL)
DESCRIPTION
A Malfunction Indicator Lamp (MIL) is standard
equipment on all instrument clusters. The MIL is
located near the lower edge of the instrument cluster
overlay, to the left of center. The MIL consists of a
stencilled cutout of the International Control and
Display Symbol icon for ªEngineº 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. 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 Light Emit-
ting Diode (LED) soldered onto the instrument clus-
ter electronic circuit board. The MIL is serviced as a
unit with the instrument cluster.
OPERATION
The Malfunction Indicator Lamp (MIL) gives an
indication to the vehicle operator when the Power-
train Control Module (PCM) has recorded a Diagnos-
tic Trouble Code (DTC) for an On-Board Diagnostics
II (OBDII) emissions-related circuit or component
malfunction. In addition, on models with a diesel
engine an Engine Control Module (ECM) supple-
ments the PCM, and can also record an OBDII DTC.
The MIL is controlled by a transistor on the instru-
ment cluster circuit board based upon cluster pro-
gramming and electronic messages received by the
cluster from the PCM or ECM over the Chrysler Col-
lision Detection (CCD) data bus. The MIL 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 LED will always be off when
the ignition switch is in any position except On or
Start. The LED only illuminates when it is provided
a path to ground by the instrument cluster transis-
tor. The instrument cluster will turn on the MIL for
the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the indicator is illuminated
for about seven seconds as a bulb test.
²PCM Lamp-On Message- Each time the clus-
ter receives a lamp-on message from the PCM or
ECM, the indicator will be illuminated. The indicator
can be flashed on and off, or illuminated solid, as dic-
tated by the PCM/ECM message. For some DTC's, if
a problem does not recur, the PCM or ECM will send
a lamp-off message automatically. Other DTC's mayrequire that a fault be repaired and the PCM or
ECM be reset before a lamp-off message will be sent.
For more information on the PCM, the ECM, and the
DTC set and reset parameters, (Refer to 25 - EMIS-
SIONS CONTROL - OPERATION).
²Communication Error- If the cluster receives
no lamp-on message from the PCM or ECM for
twenty seconds, the MIL is illuminated by the instru-
ment cluster to indicate a loss of bus communication.
The indicator remains controlled and illuminated by
the cluster until a valid lamp-on message is received
from the PCM or ECM.
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 PCM/ECM continually monitor the fuel and
emissions system circuits and sensors to decide
whether the system is in good operating condition.
The PCM/ECM then sends the proper lamp-on or
lamp-off messages to the instrument cluster. For fur-
ther diagnosis of the MIL or the instrument cluster
circuitry that controls the LED, (Refer to 8 - ELEC-
TRICAL/INSTRUMENT CLUSTER - DIAGNOSIS
AND TESTING). If the instrument cluster turns on
the MIL after the bulb test, it may indicate that a
malfunction has occurred and that the fuel and emis-
sions systems may require service. For proper diag-
nosis of the fuel and emissions systems, the PCM,
the ECM, the CCD data bus, or the message inputs
to the instrument cluster that control the MIL, a
DRBIIItscan tool is required. Refer to the appropri-
ate diagnostic information.
ODOMETER
DESCRIPTION
An odometer and trip odometer are standard
equipment in all instrument clusters. The odometer
and trip odometer information are displayed in a
common electronic Vacuum-Fluorescent Display
(VFD), which is visible through a small window cut-
out located in the left lower quadrant of the cluster
overlay. However, the odometer and trip odometer
information are not displayed simultaneously. The
trip odometer reset switch on the instrument cluster
circuit board toggles the display between odometer
and trip odometer modes by depressing the odometer/
trip odometer switch knob that extends through the
lower edge of the cluster lens, just right of the
tachometer. Both the odometer and the trip odometer
information is stored in the instrument cluster mem-
ory.
8J - 24 INSTRUMENT CLUSTERBR/BE

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

CENTER HIGH MOUNTED
STOP LAMP
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the CHMSL from the roof panel.
(3) Rotate sockets 1/4 turn clockwise and remove
from lamp. (The two center bulbs light the stoplamp
and the outside bulbs light the cargo lamp, if
equipped.)
(4) Pull bulb from socket.
INSTALLATION
(1) Push bulb into socket.
(2) Position socket in lamp an rotate socket 1/4
turn counterclockwise.
(3) Install the CHMSL.
(4) Connect the battery negative cable.
CENTER HIGH MOUNTED
STOP LAMP UNIT
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove screws holding CHMSL to roof panel
(Fig. 4).
(3) Separate CHMSL from roof.
(4) Disengage wire connector from body wire har-
ness.
(5) Separate CHMSL from vehicle.
INSTALLATION
(1) Position lamp at cab roof and connect wire con-
nector.
(2) Install screws holding CHMSL to roof panel.
Tighten securely.
(3) Connect the battery negative cable.
CLEARANCE LAMP
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove screws holding clearance lamp lens to
roof panel (Fig. 5).
(3) Rotate socket 1/4 turn counterclockwise and
separate socket from lamp.
INSTALLATION
(1) Install socket in lamp and rotate socket 1/4
turn clockwise.
(2) Position clearance lamp on roof.
(3) Install screws holding clearance lamp lens to
roof panel. Tighten to 1 N´m (13 in. lbs.).
(4) Connect the battery negative cable.
Fig. 3 Brake Lamp Switch
1 - TAB NOTCH (IN BRACKET)
2 - SWITCH PLUNGER
3 - SWITCH TAB
Fig. 4 Center High Mounted Stop Lamp
1 - CHMSL CARGO LAMP HOUSING
2 - CHMSL
3 - CARGO LAMPS
4 - SCREW
5 - CLIP
6 - CAB
8L - 6 LAMPS/LIGHTING - EXTERIORBR/BE
BRAKE LAMP SWITCH (Continued)