2003 DODGE RAM Actuator

layer of the overlay causes the icon to appear in red
through the translucent outer layer of the overlay
when the indicator is illuminated from behind by the
LED, which is soldered onto the instrument cluster
electronic circuit board. The ETC indicator is ser-
viced as a unit with the instrument cluster.
OPERATION
The Electronic Throttle Control (ETC) indicator
gives an indication to the vehicle operator when the
ETC system is faulty or inoperative. The ETC indi-
cator is controlled by a transistor on the instrument
cluster circuit board based upon cluster programming
and electronic messages received by the cluster from
the Powertrain Control Module (PCM) over the Pro-
grammable Communications Interface (PCI) data
bus. The ETC indicator Light Emitting Diode (LED)
is completely controlled by the instrument cluster
logic circuit, and that logic will only allow this indi-
cator to operate when the instrument cluster receives
a battery current input on the fused ignition switch
output (run-start) circuit. Therefore, the LED will
always be off when the ignition switch is in any posi-
tion except On or Start. The LED only illuminates
when it is provided a path to ground by the instru-
ment cluster transistor. The instrument cluster will
turn on the ETC indicator for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the ETC indicator is illu-
minated for about six seconds. The entire six second
bulb test is a function of the PCM.
²ETC Lamp-On Message- Each time the clus-
ter receives a lamp-on message from the PCM, the
ETC indicator will be illuminated. The indicator can
be flashed on and off, or illuminated solid, as dic-
tated by the PCM message. The indicator remains
illuminated solid or continues to flash for about
twelve seconds or until the cluster receives a lamp-off
message from the PCM, whichever is longer. If the
indicator is illuminated solid with the engine run-
ning the vehicle will usually remain drivable. If the
indicator is flashing with the engine running the
vehicle may require towing. A flashing indicator
means the ETC system requires immediate service.
²Communication Error- If the cluster receives
no ETC lamp messages for three consecutive seconds,
the ETC indicator is illuminated. The indicator
remains illuminated until the cluster receives a sin-
gle lamp-off message from the PCM.
²Actuator Test- Each time the cluster is put
through the actuator test, the ETC indicator will be
turned on, then off again during the bulb check por-
tion of the test to confirm the functionality of the
LED and the cluster control circuitry. The actuator
test illumination of the ETC indicator is a function of
the PCM.The PCM continually monitors the ETC system cir-
cuits and sensors to decide whether the system is in
good operating condition. The PCM then sends the
proper lamp-on or lamp-off messages to the instru-
ment cluster. If the PCM sends a lamp-on message
after the bulb test, it indicates that the PCM has
detected a system malfunction and/or that the ETC
system is inoperative. The PCM will store a Diagnos-
tic Trouble Code (DTC) for any malfunction it
detects. Each time the ETC indicator fails to illumi-
nate due to an open or short in the cluster ETC indi-
cator circuit, the cluster sends a message notifying
the PCM of the condition, the instrument cluster and
the PCM will each store a DTC. For proper diagnosis
of the ETC system, the PCM, the PCI data bus, or
the electronic message inputs to the instrument clus-
ter that control the ETC indicator, 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
left quadrant of the instrument cluster, below the
voltage gauge. The fuel gauge consists 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 ªEº (or
Empty) to ªFº (or Full). An International Control and
Display Symbol icon for ªFuelº is located on the clus-
ter overlay, directly below the right end of the gauge
scale. An arrowhead pointed to the left side of the
vehicle is imprinted on the cluster overlay next to the
ªFuelº icon in the fuel gauge to provide the driver
with a reminder as to the location of the fuel filler
access. On vehicles equipped with a diesel engine,
text that specifies ªDIESEL ONLYº is located across
the fuel gauge below the gauge scale, but above the
hub of the gauge needle. The fuel gauge graphics are
black against a white field except for a single red
graduation at the low 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 black graph-
ics appear blue and the red graphics still appear red.
The orange gauge needle is internally illuminated.
Gauge illumination is provided by replaceable incan-
descent bulb and bulb holder units located on the
instrument cluster electronic circuit board. The fuel
gauge is serviced as a unit with the instrument clus-
ter.
DRINSTRUMENT CLUSTER 8J - 25
ETC INDICATOR (Continued)

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 cluster programming and elec-
tronic messages received by the cluster from the
Powertrain Control Module (PCM) on vehicles
equipped with a gasoline engine, or from the Engine
Control Module (ECM) on vehicles equipped with a
diesel engine over the Programmable Communica-
tions Interface (PCI) data bus. The fuel gauge is an
air core magnetic unit that receives battery current
on the instrument cluster electronic circuit board
through the fused ignition switch output (run-start)
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 or ECM
indicating the percent tank full, the cluster program-
ming applies an algorithm to calculate the proper
gauge needle position, then moves the gauge needle
to the proper relative position on the gauge scale.
The algorithm is used to dampen gauge needle move-
ment against the negative effect that fuel sloshing
within the fuel tank can have on accurate inputs
from the fuel tank sending unit to the PCM or ECM.
²Less Than Twenty Percent Tank Full Mes-
sage- Each time the cluster receives messages from
the PCM or ECM indicating the percent tank full is
about twenty percent or less for ten consecutive sec-
onds and the vehicle speed is zero, or for sixty con-
secutive seconds and the vehicle speed is greater
than zero, the gauge needle is moved to the one-
eighth graduation or below on the gauge scale, the
low fuel indicator is illuminated, and a single chime
tone is sounded. The low fuel indicator remains illu-
minated until the cluster receives messages from the
PCM or ECM indicating that the percent tank full is
greater than about twenty percent for ten consecu-
tive seconds and the vehicle speed is zero, or for sixty
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 or ECM.
²Less Than Empty Percent Tank Full Mes-
sage- Each time the cluster receives a message from
the PCM or ECM indicating the percent tank full is
less than empty, the gauge needle is moved to the far
left end of the gauge scale and the low fuel indicatoris illuminated immediately. This message would indi-
cate that the fuel tank sender input to the PCM or
ECM is a short circuit.
²More Than Full Percent Tank Full Message
- Each time the cluster receives a message from the
PCM or ECM indicating the percent tank full is more
than full, the gauge needle is moved to the far left
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 or
ECM is an open circuit.
²Communication Error- If the cluster fails to
receive a percent tank full message, it will hold the
gauge needle at the last indication about five seconds
or until the ignition switch is turned to the Off posi-
tion, whichever occurs first. After five seconds, the
cluster will move the gauge needle to the low end of
the gauge scale.
²Actuator Test- Each time the cluster is put
through the actuator test, the fuel gauge needle will
be swept to several calibration points on the gauge
scale in a prescribed sequence in order to confirm the
functionality of the gauge and the cluster control cir-
cuitry.
On vehicles with a gasoline engine, the PCM con-
tinually monitors the fuel tank sending unit to deter-
mine the level of the fuel in the fuel tank. On
vehicles with a diesel engine, the ECM continually
monitors the fuel tank sending unit to determine the
level of the fuel in the fuel tank. The PCM or ECM
then sends the proper fuel level 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 ECM, the PCI data bus, or the elec-
tronic message inputs to the instrument cluster that
control the fuel gauge, a DRBIIItscan tool is
required. Refer to the appropriate diagnostic infor-
mation.
GEAR SELECTOR INDICATOR
DESCRIPTION
An electronic automatic transmission gear selector
indicator is standard factory-installed equipment on
this model. The gear selector indicator information is
displayed in a Vacuum-Fluorescent Display (VFD)
unit. The VFD is soldered onto the cluster electronic
circuit board and is visible through a window with a
smoked clear lens located on the lower edge of the
speedometer gauge dial face of the cluster overlay.
The dark lens over the VFD prevents the indicator
from being clearly visible when it is not illuminated.
8J - 26 INSTRUMENT CLUSTERDR
FUEL GAUGE (Continued)

The gear selector indicator displays the following
characters 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 column. The VFD illuminates a rect-
angular box around the character that represents the
currently selected lever position.
The gear selector indicator characters and graphics
appear in the same blue-green color and at the same
lighting level as the odometer/trip odometer informa-
tion when illuminated by the instrument cluster elec-
tronic circuit board. During daylight hours (exterior
lamps Off) the gear selector indicator VFD is illumi-
nated at full brightness for clear visibility. At night
(exterior lamps are On) the VFD lighting level is
adjusted with the other cluster illumination lamps
using the panel lamps dimmer thumbwheel on the
headlamp switch. However, a ªParadeº mode position
of the panel lamps dimmer thumbwheel allows the
VFD to be illuminated at full brightness when the
vehicle is driven in daylight hours with the exterior
lamps turned On. The gear selector indicator VFD is
serviced as a unit with the instrument cluster.
OPERATION
The electronic gear selector indicator gives an indi-
cation to the vehicle operator of the transmission
gear that has been selected with the automatic trans-
mission gear selector lever. This indicator is con-
trolled by the instrument cluster circuit board based
upon cluster programming. The cluster circuitry
automatically configures itself for the proper trans-
mission and automatic transmission model based
upon the hard wired transmission range sensor mux
circuit input to the cluster. The gear selector indica-
tor information is displayed by a dedicated Vacuum
Fluorescent Display (VFD) unit on the instrument
cluster electronic circuit board, and the VFD will not
display the gear selector indicator information after
the ignition switch is turned to the Off position. The
instrument cluster circuitry configures the gear selec-
tor indicator VFD based upon the following inputs
from the transmission range sensor:
²Open Circuit- If the cluster is configured for
an automatic transmission and the transmission
range sensor mux circuit is open, the cluster circuitry
controls the gear selector indicator display based
upon electronic messages received from the electronic
Transmission Control Module (TCM) over the Pro-
grammable Communications Interface (PCI) data
bus. If the transmission range sensor mux circuit is
open and no electronic messages are received from
the TCM within two seconds, the instrument cluster
circuitry will not display any gear selector position
until the condition is resolved or until the ignitionswitch is turned to the Off position, whichever occurs
first.
²Resolved Circuit- If the transmission range
sensor mux circuit is resolved, the cluster circuitry
controls the gear selector indicator display based
upon the resistance value of the hard wired input
from the transmission range sensor. If the cluster is
configured for an automatic transmission with a
transmission range sensor input and detects a short
to ground or an open in the transmission range sen-
sor mux input, the instrument cluster circuitry will
not display any gear selector position in the VFD.
The VFD display for the short-to-ground and open
circuit conditions will continue until the condition is
resolved 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 gear selector indicator
VFD will display all of its characters at once during
the VFD portion of the test to confirm the function-
ality of the VFD and the cluster control circuitry.
On models with a TCM, the TCM continually mon-
itors the transmission range sensor, then sends the
proper gear selector indicator position messages to
the instrument cluster. On models without a TCM,
the instrument cluster continually monitors the hard
wired transmission range sensor multiplexed input.
For further diagnosis of the gear selector indicator or
the instrument cluster circuitry that controls this
function, (Refer to 8 - ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING). For fur-
ther diagnosis of the transmission range sensor on
models without a TCM, (Refer to 21 - TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - 42RE/TRANS-
MISSION RANGE SENSOR - DIAGNOSIS AND
TESTING) or (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 46RE/TRANSMISSION
RANGE SENSOR - DIAGNOSIS AND TESTING).
On models with a TCM, for proper diagnosis of the
transmission range sensor, the TCM, the PCI data
bus, or the electronic message inputs to the instru-
ment cluster that control the gear selector indicator,
a DRBIIItscan tool is required. Refer to the appro-
priate diagnostic information.
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 clus-
ter, between the tachometer and the speedometer.
The high beam indicator consists of a stencil-like cut-
out of the International Control and Display Symbol
icon for ªHigh Beamº in the opaque layer of the
DRINSTRUMENT CLUSTER 8J - 27
GEAR SELECTOR INDICATOR (Continued)

instrument cluster overlay. The dark outer layer of
the overlay prevents the indicator from being clearly
visible when the it is not illuminated. A blue Light
Emitting Diode (LED) behind the cutout in the
opaque layer of the overlay causes the icon to appear
in blue through the translucent outer layer of the
overlay when the indicator is illuminated from
behind by the LED, which is soldered onto the
instrument cluster electronic circuit board. The high
beam indicator is serviced as a unit with the instru-
ment cluster.
OPERATION
The high beam indicator gives an indication to the
vehicle operator whenever the headlamp high beams
are illuminated. This indicator is controlled by a
transistor on the instrument cluster circuit board
based upon cluster programming and a hard wired
multiplex input received by the cluster from the
headlamp beam select switch circuitry of the multi-
function switch on the washer/beam select switch
mux circuit. The high beam indicator Light Emitting
Diode (LED) is completely controlled by the instru-
ment cluster logic circuit, and that logic will allow
this indicator to operate whenever the instrument
cluster receives a battery current input on the fused
B(+) circuit. Therefore, the LED can be illuminated
regardless of the ignition switch position. The LED
only illuminates when it is provided a path to ground
by the instrument cluster transistor. The instrument
cluster will turn on the high beam indicator for the
following reasons:
²High Beam Headlamps-On Input- Each time
the cluster detects a high beam headlamps-on input
from the headlamp beam select switch circuitry of
the multi-function switch on the washer/beam select
switch mux circuit, the headlamp high beams and
the high beam indicator will be illuminated. The
headlamp high beams and the high beam indicator
remain illuminated until the cluster receives a high
beam headlamps-off input from the multi-function
switch, or until the exterior lamp load shedding (bat-
tery saver) timed interval expires, whichever occurs
first.
²Actuator Test- Each time the cluster is put
through the actuator test, the high beam indicator
will be turned on, then off again during the bulb
check portion of the test to confirm the functionality
of the LED and the cluster control circuitry.
The instrument cluster continually monitors the
headlamp switch and the multi-function switch to
determine the proper headlamp low beam and high
beam control. The instrument cluster then sends the
proper low beam and high beam lamp-on and lamp-
off messages to the Front Control Module (FCM) over
the Programmable Communications Interface (PCI)data bus and turns the high beam indicator on or off
accordingly. For further diagnosis of the high beam
indicator or the instrument cluster circuitry that con-
trols the indicator, (Refer to 8 - ELECTRICAL/IN-
STRUMENT CLUSTER - DIAGNOSIS AND
TESTING). For proper diagnosis of the headlamps, or
the headlamp switch and multi-function switch
inputs to the instrument cluster that control the high
beam indicator, a DRBIIItscan tool is required.
Refer to the appropriate diagnostic information.
LAMP OUT INDICATOR
DESCRIPTION
A lamp out indicator is standard equipment on all
instrument clusters. The lamp out indicator consists
of the words ªLAMP OUTº, which appear in the
lower portion of the odometer/trip odometer Vacuum-
Fluorescent Display (VFD) unit. The VFD is soldered
onto the cluster electronic circuit board and is visible
through a window with a smoked clear lens located
on the lower edge of the tachometer gauge dial face
of the cluster overlay. The dark lens over the VFD
prevents the indicator from being clearly visible
when it is not illuminated. The words ªLAMP OUTº
appear in an amber color and at the same lighting
level as the odometer/trip odometer information
when they are illuminated by the instrument cluster
electronic circuit board. The lamp out indicator is
serviced as a unit with the VFD in the instrument
cluster.
OPERATION
The lamp out indicator gives an indication to the
vehicle operator when an exterior lamp has failed.
This indicator is controlled by the instrument cluster
circuit board based upon cluster programming and
electronic messages received by the cluster from the
Front Control Module (FCM) over the Programmable
Communications Interface (PCI) data bus. The lamp
out indicator is completely controlled by the instru-
ment cluster logic circuit, and that logic will only
allow this indicator to operate when the instrument
cluster receives a battery current input on the fused
ignition switch output (run-start) circuit. Therefore,
the indicator will always be off when the ignition
switch is in any position except On or Start. The
indicator only illuminates when it is switched to
ground by the instrument cluster circuitry. The
instrument cluster will turn on the lamp out indica-
tor for the following reasons:
²Lamp Out Indicator Lamp-On Message-
Each time the cluster receives a lamp out indicator
lamp-on message from the FCM indicating that an
inoperative headlamp (low or high beam), turn signal
8J - 28 INSTRUMENT CLUSTERDR
HIGH BEAM INDICATOR (Continued)

lamp, or brake lamp (excluding Center High
Mounted Stop Lamp [CHMSL]) circuit has been
detected, the lamp out indicator is illuminated. The
indicator remains illuminated until the cluster
receives a lamp out indicator lamp-off message from
the FCM 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 lamp out indicator will
be turned on, then off again during the VFD portion
of the test to confirm the functionality of the VFD
and the cluster control circuitry.
The FCM monitors each of the headlamp, turn sig-
nal lamp, and brake lamp (except CHMSL) circuits to
determine the condition of these exterior lamps. The
FCM then sends the proper lamp out indicator
lamp-on and lamp-off messages to the instrument
cluster. For further diagnosis of the lamp out indica-
tor or the instrument cluster circuitry that controls
the indicator, (Refer to 8 - ELECTRICAL/INSTRU-
MENT CLUSTER - DIAGNOSIS AND TESTING).
For proper diagnosis of the exterior lighting system
circuits, the FCM, the PCI data bus, or the electronic
message inputs to the instrument cluster that control
the lamp out indicator, a DRBIIItscan tool is
required. Refer to the appropriate diagnostic infor-
mation.
LOW FUEL INDICATOR
DESCRIPTION
A low fuel indicator is standard equipment on all
instrument clusters. The low fuel indicator is located
on the left side of the instrument cluster, to the left
of the fuel gauge. The low fuel indicator consists of a
stencil-like 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
Light Emitting Diode (LED) 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 the LED, which is soldered onto the
instrument cluster electronic circuit board. The low
fuel indicator is serviced as a unit with the instru-
ment cluster.
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) on vehicles equipped with a
gasoline engine, or from the Engine Control Module
(ECM) on vehicles equipped with a diesel engine over
the Programmable Communications Interface (PCI)
data bus. The low fuel indicator Light Emitting
Diode (LED) is completely controlled by the instru-
ment cluster logic circuit, and that logic will only
allow this indicator to operate when the instrument
cluster receives a battery current input on the fused
ignition switch output (run-start) circuit. 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 transistor. The instrument
cluster will turn on the low fuel indicator for the fol-
lowing reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the low fuel indicator is
illuminated for about two seconds as a bulb test.
²Less Than Twenty Percent Tank Full Mes-
sage- Each time the cluster receives messages from
the PCM or ECM indicating the percent tank full is
about twenty percent or less for ten consecutive sec-
onds and the vehicle speed is zero, or for sixty con-
secutive seconds and the vehicle speed is greater
than zero, the fuel gauge needle is moved to the one-
eighth graduation or below on the gauge scale, the
low fuel indicator is illuminated and a single chime
tone is sounded. The low fuel indicator remains illu-
minated until the cluster receives messages from the
PCM or ECM indicating that the percent tank full is
greater than about twenty percent for ten consecu-
tive seconds and the vehicle speed is zero, or for sixty
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 or ECM.
²Less Than Empty Percent Tank Full Mes-
sage- Each time the cluster receives a message from
the PCM or ECM indicating the percent tank full is
less than empty, the low fuel indicator is illuminated
immediately. This message would indicate that the
fuel tank sender input to the PCM or ECM is a short
circuit.
²More Than Full Percent Tank Full Message
- Each time the cluster receives a message from the
PCM or ECM indicating the percent tank full is more
than full, the low fuel indicator is illuminated imme-
diately. This message would indicate that the fuel
tank sender input to the PCM or ECM is an open cir-
cuit.
DRINSTRUMENT CLUSTER 8J - 29
LAMP OUT INDICATOR (Continued)

²Actuator Test- Each time the cluster is put
through the actuator test, the low fuel indicator will
be turned on, then off again during the bulb check
portion of the test to confirm the functionality of the
LED and the cluster control circuitry.
On vehicles with a gasoline engine, the PCM con-
tinually monitors the fuel tank sending unit to deter-
mine the level of fuel in the fuel tank. On vehicles
with a diesel engine, the ECM continually monitors
the fuel tank sending unit to determine the level of
fuel in the fuel tank. The PCM or ECM then sends
the proper fuel level 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/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING). For
proper diagnosis of the fuel tank sending unit, the
PCM, the ECM, the PCI data bus, or the electronic
message inputs to the instrument cluster that control
the low fuel indicator, a DRBIIItscan tool is
required. Refer to the appropriate diagnostic infor-
mation.
MALFUNCTION INDICATOR
LAMP (MIL)
DESCRIPTION
A Malfunction Indicator Lamp (MIL) is standard
equipment on all instrument clusters. The MIL is
located on the left side of the instrument cluster, to
the left of the voltage gauge. The MIL consists of a
stencil-like 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
Light Emitting Diode (LED) 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 the LED, which is soldered onto the
instrument cluster 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) on vehicles with a gaso-
line engine, or the Engine Control Module (ECM) on
vehicles with a diesel engine has recorded a Diagnos-
tic Trouble Code (DTC) for an On-Board Diagnostics
II (OBDII) emissions-related circuit or component
malfunction. The MIL is controlled by a transistor on
the instrument cluster circuit board based upon clus-
ter programming and electronic messages received bythe cluster from the PCM or ECM over the Program-
mable Communications Interface (PCI) data bus. The
MIL Light Emitting Diode (LED) is completely con-
trolled by the instrument cluster logic circuit, and
that logic will only allow this indicator to operate
when the instrument cluster receives a battery cur-
rent input on the fused ignition switch output (run-
start) circuit. 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 cluster
transistor. 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 two seconds as a bulb test. The entire two
second bulb test is a function of the PCM or ECM.
²MIL Lamp-On Message- Each time the clus-
ter receives a MIL lamp-on message from the PCM
or ECM, the indicator will be illuminated. The indi-
cator can be flashed on and off, or illuminated solid,
as dictated by the PCM or 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 may require 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 -
EMISSIONS CONTROL - OPERATION).
²Communication Error- If the cluster receives
no lamp-on message from the PCM or ECM for ten
seconds, the MIL is illuminated by the instrument
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 MIL 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.
On vehicles with a gasoline engine, the PCM con-
tinually monitors the fuel and emissions system cir-
cuits and sensors to decide whether the system is in
good operating condition. On vehicles with a diesel
engine, the ECM continually monitors the fuel and
emissions system circuits and sensors to decide
whether the system is in good operating condition.
The PCM or 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-
8J - 30 INSTRUMENT CLUSTERDR
LOW FUEL INDICATOR (Continued)

must be displaying the odometer information when
the trip odometer reset switch button is pressed in
order to toggle to the engine hours display. The
engine hours will remain displayed for about thirty
seconds, until the engine speed message is greater
than zero, or until the ignition switch is turned to
the Off position, whichever occurs first.
²Trip Odometer Reset- When the trip odome-
ter reset switch button is pressed and held for longer
than about two seconds with the ignition switch in
the On or Start positions, the trip odometer will be
reset to 0.0 kilometers (miles). The VFD must be dis-
playing the trip odometer information in order for
the trip odometer information to be reset.
²Communication Error- If the cluster fails to
receive a distance message during normal operation,
it will hold and display the last data received until
the ignition switch is turned to the Off position. If
the cluster does not receive a distance message
within one second after the ignition switch is turned
to the On position, it will display the last distance
message stored in the cluster memory. If the cluster
is unable to display distance information due to an
error internal to the cluster, the VFD display will be
dashes.
²Actuator Test- Each time the cluster is put
through the actuator test, the odometer VFD will dis-
play all of its segments simultaneously during the
VFD portion of the test to confirm the functionality
of each of the VFD segments and the cluster control
circuitry.
The PCM continually monitors the vehicle speed
pulse information received from the vehicle speed
sensor and engine speed pulse information received
from the crankshaft position sensor, then sends the
proper distance and engine speed messages to the
instrument cluster. For further diagnosis of the
odometer/trip odometer or the instrument cluster cir-
cuitry that controls these functions, (Refer to 8 -
ELECTRICAL/INSTRUMENT CLUSTER - DIAGNO-
SIS AND TESTING). For proper diagnosis of the
vehicle speed sensor, the crankshaft position sensor,
the PCM, the PCI data bus, or the electronic message
inputs to the instrument cluster that control the
odometer/trip odometer, a DRBIIItscan tool is
required. Refer to the appropriate diagnostic infor-
mation.
OIL PRESSURE GAUGE
DESCRIPTION
An oil pressure gauge is standard equipment on all
instrument clusters. The oil pressure gauge is located
in the upper right quadrant of the instrument clus-
ter, above the coolant temperature gauge. The oilpressure gauge consists 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 ªLº (or Low) to ªHº (or
High) for gasoline engines. On vehicles with a diesel
engine the scale reads from ª0º kPa to ª760º kPa in
markets where a metric instrument cluster is speci-
fied, or from ª0º psi to ª110º psi in all other markets.
An International Control and Display Symbol icon for
ªEngine Oilº is located on the cluster overlay, directly
below the left end of the gauge scale. The oil pres-
sure gauge graphics are black against a white field
except for two red graduations at the low 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 black graphics appear blue and the
red graphics still appear red. The orange gauge nee-
dle is internally illuminated. Gauge illumination is
provided by replaceable incandescent bulb and bulb
holder units located on the instrument cluster elec-
tronic circuit board. The oil pressure gauge is ser-
viced as a unit with the instrument cluster.
OPERATION
The oil pressure gauge gives an indication to the
vehicle operator of the engine oil pressure. This
gauge is controlled by the instrument cluster circuit
board based upon cluster programming and elec-
tronic messages received by the cluster from the
Powertrain Control Module (PCM) on vehicles with a
gasoline engine, or from the Engine Control Module
(ECM) on vehicles equipped with a diesel engine over
the Programmable Communications Interface (PCI)
data bus. The oil pressure gauge 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 (run-start) circuit when-
ever the ignition switch is in the On or Start posi-
tions. The cluster is programmed to move the gauge
needle back to the low end of the scale after the igni-
tion switch is turned to the Off position. The instru-
ment cluster circuitry controls the gauge needle
position and provides the following features:
²Engine Oil Pressure Message- The instru-
ment cluster circuitry restricts the oil pressure gauge
needle operation in order to provide readings that
are consistent with customer expectations. Each time
the cluster receives a message from the PCM or ECM
indicating the engine oil pressure is above about 41
kPa (6 psi) the cluster holds the gauge needle at a
point near the middle increment within the normal
range on the gauge scale.
²Engine Oil Pressure Low Message- Each
time the cluster receives a message from the PCM or
8J - 32 INSTRUMENT CLUSTERDR
ODOMETER (Continued)

ECM indicating the engine oil pressure is below
about 41 kPa (6 psi), the gauge needle is moved to
the graduation at the far left end of the gauge scale,
the check gauges indicator is illuminated, and a sin-
gle chime tone is generated. The gauge needle
remains at the left end of the gauge scale and the
check gauges indicator remains illuminated until the
cluster receives a message from the PCM or ECM
indicating that the engine oil pressure is above about
41 kPa (6 psi), or until the ignition switch is turned
to the Off position, whichever occurs first. The clus-
ter will only turn the check gauges indicator on in
response to an engine oil pressure low message if the
engine speed message is greater than zero.
²Communication Error- If the cluster fails to
receive an engine oil pressure message, it will hold
the gauge needle at the last indication about five sec-
onds or until the ignition switch is turned to the Off
position, whichever occurs first. After five seconds,
the cluster will move the gauge needle to the left end
of the gauge scale.
²Actuator Test- Each time the cluster is put
through the actuator test, the oil pressure gauge nee-
dle will be swept to several calibration points on the
gauge scale in a prescribed sequence in order to con-
firm the functionality of the gauge and the cluster
control circuitry.
On vehicles with a gasoline engine, the PCM con-
tinually monitors the engine oil pressure sensor to
determine the engine oil pressure. On vehicles with a
diesel engine, the ECM continually monitors the
engine oil pressure sensor to determine the engine oil
pressure. The PCM or ECM then sends the proper
engine oil pressure messages to the instrument clus-
ter. For further diagnosis of the oil pressure gauge or
the instrument cluster circuitry that controls the
gauge, (Refer to 8 - ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING). If the
instrument cluster turns on the check gauges indica-
tor due to a low oil pressure gauge reading, it may
indicate that the engine or the engine oiling system
requires service. For proper diagnosis of the engine
oil pressure sensor, the PCM, the ECM, the PCI data
bus, or the electronic message inputs to the instru-
ment cluster that control the oil pressure gauge, a
DRBIIItscan tool is required. Refer to the appropri-
ate diagnostic information.
OVERDRIVE OFF INDICATOR
DESCRIPTION
An overdrive off indicator is standard equipment
on all instrument clusters. However, on vehicles not
equipped with the optional overdrive automatic
transmission, this indicator is electronically disabled.The overdrive off indicator consists of the words ªO/D
OFFº, which appear in the lower portion of the odom-
eter/trip odometer indicator Vacuum Fluorescent Dis-
play (VFD) unit. The VFD is soldered onto the
cluster electronic circuit board and is visible through
a window with a smoked clear lens located on the
lower edge of the tachometer gauge dial face of the
cluster overlay. The dark lens over the VFD prevents
the indicator from being clearly visible when it is not
illuminated. The words ªO/D OFFº appear in an
amber color and at the same lighting level as the
odometer/trip odometer information when they are
illuminated by the instrument cluster electronic cir-
cuit board. The overdrive off indicator is serviced as
a unit with the VFD in the instrument cluster.
OPERATION
The overdrive off indicator gives an indication to
the vehicle operator when the Off position of the
overdrive off switch has been selected, disabling the
electronically controlled overdrive feature of the auto-
matic transmission. This indicator is controlled by
the instrument cluster circuit board based upon clus-
ter programming and electronic messages received by
the cluster from the Powertrain Control Module
(PCM) over the Programmable Communications
Interface (PCI) data bus. The overdrive off indicator
is completely controlled by the instrument cluster
logic circuit, and that logic will only allow this indi-
cator to operate when the instrument cluster receives
a battery current input on the fused ignition switch
output (run-start) circuit. Therefore, the indicator
will always be off when the ignition switch is in any
position except On or Start. The indicator only illu-
minates when it is switched to ground by the instru-
ment cluster circuitry. The instrument cluster will
turn on the overdrive off indicator for the following
reasons:
²Overdrive Off Lamp-On Message- Each time
the cluster receives an overdrive off lamp-on message
from the PCM indicating that the Off position of the
overdrive off switch has been selected, the overdrive
off indicator will be illuminated. The indicator
remains illuminated until the cluster receives an
overdrive off lamp-off message from the PCM, 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 overdrive off indicator
will be turned on, then off again during the VFD por-
tion of the test to confirm the functionality of the
VFD and the cluster control circuitry.
The PCM continually monitors the overdrive off
switch to determine the proper outputs to the auto-
matic transmission. The PCM then sends the proper
overdrive off lamp-on and lamp-off messages to the
DRINSTRUMENT CLUSTER 8J - 33
OIL PRESSURE GAUGE (Continued)