Vacuum DODGE RAM 2003 Service Owner's Manual

ACTUATOR TEST
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, SEAT BELT TENSIONER,
SIDE CURTAIN AIRBAG, OR INSTRUMENT PANEL
COMPONENT DIAGNOSIS OR SERVICE. DISCON-
NECT AND ISOLATE THE BATTERY NEGATIVE
(GROUND) CABLE, THEN WAIT TWO MINUTES FOR
THE SYSTEM CAPACITOR TO DISCHARGE BEFORE
PERFORMING FURTHER DIAGNOSIS OR SERVICE.
THIS IS THE ONLY SURE WAY TO DISABLE THE
SUPPLEMENTAL RESTRAINT SYSTEM. FAILURE TO
TAKE THE PROPER PRECAUTIONS COULD
RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT
AND POSSIBLE PERSONAL INJURY.
The instrument cluster actuator test will put the
instrument cluster into its self-diagnostic mode. In
this mode the instrument cluster can perform a self-
diagnostic test that will confirm that the instrument
cluster circuitry, the gauges, and the indicators are
capable of operating as designed. During the actuator
test the instrument cluster circuitry will position
each of the gauge needles at various calibration
points, illuminate all of the segments in the Vacuum
Fluorescent Display (VFD) units, turn all of the indi-
cators on and off again, display any Diagnostic Trou-
ble Code (DTC) information, and display the number
of ignition key cycles that have occurred since the
DTC was detected. It is suggested that a note pad
and pencil be used to write down any fault informa-
tion that is displayed during the test for reference.
Successful completion of the actuator test will con-
firm that the instrument cluster is operational. How-
ever, there may still be a problem with the PCI data
bus, the Powertrain Control Module (PCM), the
Engine Control Module (ECM), the Front Control
Module (FCM), the Transmission Control Module
(TCM), the Transfer Case Control Module (TCCM),
the Airbag Control Module (ACM), the Controller
Anti-lock Brake (CAB), or the inputs to one of these
electronic control modules. Use a DRBIIItscan toolto diagnose these components. Refer to the appropri-
ate diagnostic information.
(1) Begin the test with the ignition switch in the
Off position.
(2) Depress the odometer/trip odometer switch but-
ton.
(3) While still holding the odometer/trip odometer
switch button depressed, turn the ignition switch to
the On position, but do not start the engine.
(4) Release the odometer/trip odometer switch but-
ton.
(5) The instrument cluster will simultaneously
illuminate all of the operational segments in both
VFD units, perform a bulb check of each operational
LED indicator. The VFD segments and LED indica-
tors remain illuminated as each gauge needle is
swept to several calibration points and back. If a
VFD segment or an LED indicator fails to illuminate,
or if a gauge needle fails to sweep through the cali-
bration points and back during this test, the instru-
ment cluster must be replaced. Following these tests,
the actuator test will proceed as described in Step 6.
(6) The text ªC Codeº is displayed in the odometer
VFD for about three seconds. If there is no stored
fault information, the display will show two pairs of
zeroes in the format ª00º ª00º, which indicate that
the display of fault information is done. If there is
stored fault information, two sets of two-digit alpha
and alpha-numeric fault codes will appear in the
odometer display for a three second interval. The
first pair of digits represents a Diagnostic Trouble
Code (DTC), or fault code for the instrument cluster.
The second pair of digits is a counter for the number
of ignition key cycles that have occurred since the
displayed DTC was set. The instrument cluster will
continue to display additional sets of two pairs of dig-
its at three second intervals until all of the stored
codes have been displayed, which is again signaled
by a code of ª00º ª00º. Refer to the Instrument Clus-
ter Failure Message table for a description of each
fault code that the instrument cluster displays. If an
instrument cluster fault is displayed, use a DRBIIIt
scan tool to diagnose the problem. Refer to the appro-
priate diagnostic information.
INSTRUMENT CLUSTER FAILURE MESSAGE
Fault Code Description Correction
01 Airbag warning indicator output circuit shorted. Refer to the appropriate diagnostic information.
02 Airbag warning indicator output circuit open. Refer to the appropriate diagnostic information.
03 ABS indicator output circuit shorted. Refer to the appropriate diagnostic information.
04 ABS indicator output circuit open. Refer to the appropriate diagnostic information.
05 MIL indicator output circuit shorted. Refer to the appropriate diagnostic information.
06 MIL indicator output circuit open. Refer to the appropriate diagnostic information.
8J - 12 INSTRUMENT CLUSTERDR
INSTRUMENT CLUSTER (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)

sions systems may require service. For proper diag-
nosis of the fuel and emissions systems, the PCM,
the ECM, the PCI data bus, or the electronic mes-
sage inputs to the instrument cluster that control the
MIL, a DRBIIItscan tool is required. Refer to the
appropriate diagnostic information.
ODOMETER
DESCRIPTION
An odometer and trip odometer are standard
equipment in all instrument clusters. The odometer,
trip odometer, and engine hours information are dis-
played in a common electronic, blue-green Vacuum-
Fluorescent Display (VFD). 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 it from being clearly visible when it is not
illuminated. However, the odometer, trip odometer,
and engine hours information are not displayed
simultaneously. The trip odometer reset switch on
the instrument cluster circuit board toggles the dis-
play between odometer and trip odometer modes by
depressing the odometer/trip odometer switch button
that extends through the lower edge of the cluster
lens, just left of the odometer VFD. When the trip
odometer information is displayed, the word ªTRIPº
is also illuminated in the upper right corner of the
VFD in a blue-green color and at the same lighting
level as the trip odometer information. The engine
hours information replaces the selected odometer or
trip odometer information whenever the ignition
switch is in the On position and the engine is not
running.
The odometer, trip odometer, and engine hours
information is stored in the instrument cluster mem-
ory. This information can be increased when the
proper inputs are provided to the instrument cluster,
but the information cannot be decreased. The odom-
eter can display values up to 999,999 kilometers
(999,999 miles). The odometer latches at these val-
ues, and will not roll over to zero. The trip odometer
can display values up to 9,999.9 kilometers (9,999.9
miles) before it rolls over to zero. The odometer dis-
play does not have a decimal point and will not show
values less than a full unit (kilometer or mile), while
the trip odometer display does have a decimal point
and will show tenths of a unit (kilometer or mile).
The unit of measure (kilometers or miles) for the
odometer and trip odometer display is not shown in
the VFD. The unit of measure for the instrument
cluster odometer/trip odometer is selected at the time
that it is manufactured, and cannot be changed.Engine hours are displayed in the format, ªhr9999º.
The cluster will accumulate values up to 9,999 hours
before the display rolls over to zero.
The odometer has a ªRental Carº mode, which will
illuminate the odometer information in the VFD
whenever the driver side front door is opened with
the ignition switch in the Off or Accessory positions.
During daylight hours (exterior lamps are Off) the
VFD is illuminated at full brightness for clear visibil-
ity. 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 if
the exterior lamps are turned On during daylight
hours.
The VFD, the trip odometer switch, and the trip
odometer switch button are serviced as a unit with
the instrument cluster.
OPERATION
The odometer and trip odometer give an indication
to the vehicle operator of the distance the vehicle has
traveled. The engine hours give an indication of the
cumulative engine-on time. This indicator is con-
trolled by the instrument cluster circuitry based
upon cluster programming and electronic messages
received by the cluster from the Powertrain Control
Module (PCM) over the Programmable Communica-
tions Interface (PCI) data bus. The odometer, trip
odometer and engine hours information is displayed
by the instrument cluster Vacuum Fluorescent Dis-
play (VFD). The VFD will display the odometer infor-
mation whenever any door is opened with the
ignition switch in the Off or Accessory positions, and
will display the last previously selected odometer or
trip odometer information when the ignition switch is
turned to the On or Start positions. The instrument
cluster circuitry controls the VFD and provides the
following features:
²Odometer/Trip Odometer Display Toggling-
Actuating the trip odometer reset switch button
momentarily with the VFD illuminated will toggle
the display between the odometer and trip odometer
information. Each time the VFD is illuminated with
the ignition switch in the On or Start positions, the
display will automatically return to the last mode
previously selected (odometer or trip odometer).
²Engine Hours Display Toggling- When the
trip odometer reset switch button is pressed and held
for longer than about six seconds with the ignition
switch in the On position and the engine speed mes-
sage from the PCM is zero, the trip odometer infor-
mation will be momentarily displayed, then the
engine hours information will be displayed. The VFD
DRINSTRUMENT CLUSTER 8J - 31
MALFUNCTION INDICATOR LAMP (MIL) (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)

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 ªSER-
VICE 4x4º appear in an amber color and at the same
lighting level as the odometer/trip odometer informa-
tion when they are illuminated by the instrument
cluster electronic circuit board. The service 4WD
indicator is serviced as a unit with the VFD in the
instrument cluster.
OPERATION
The service 4WD indicator gives an indication to
the vehicle operator when the Transfer Case Control
Module (TCCM) has recorded a Diagnostic Trouble
Code (DTC) for an electronic transfer case circuit or
component malfunction. This indicator is controlled
by a transistor on the instrument cluster circuit
board based upon cluster programming and elec-
tronic messages received by the cluster from the
TCCM over the Programmable Communications
Interface (PCI) data bus. The service 4WD 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 service 4WD indicator for the following
reasons:
²Service 4WD Lamp-On Message- Each time
the cluster receives a service 4WD lamp-on message
from the TCCM, the indicator will be illuminated.
The indicator remains illuminated until the cluster
receives a service 4WD lamp-off message from the
TCCM, or until the ignition switch is turned to the
Off position, whichever occurs first.
²Communication Error- If the cluster receives
no messages from the TCCM for five seconds, the
service 4WD indicator is illuminated by the instru-
ment cluster to indicate a loss of TCCM communica-
tion. The indicator remains controlled and
illuminated by the cluster until a valid message is
received from the TCCM.
²Actuator Test- Each time the cluster is put
through the actuator test, the service 4WD 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 TCCM continually monitors the electronic
transfer case switch and circuits to determine the
condition of the system. The TCCM then sends the
proper lamp-on or lamp-off messages to the instru-
ment cluster. For further diagnosis of the service
4WD indicator or the instrument cluster circuitry
that controls the VFD, (Refer to 8 - ELECTRICAL/
INSTRUMENT CLUSTER - DIAGNOSIS AND
TESTING). For proper diagnosis of the TCCM, the
PCI data bus, or the electronic message inputs to the
instrument cluster that control the service 4WD indi-
cator, a DRBIIItscan tool is required. Refer to the
appropriate diagnostic information.SPEEDOMETER
DESCRIPTION
A speedometer is standard equipment on all instru-
ment clusters. The speedometer is located next to the
tachometer, just to the right of center in 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 ª0º to ª120º mph, or from ª0º to ª200º km/h,
depending upon the market for which the vehicle is
manufactured. 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 (i.e.: MPH or km/h),
followed by the unit of measure for the secondary
scale. The speedometer graphics are black (primary
scale) and blue (secondary scale) against a white
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 black graphics appear dark blue and the blue
graphics appear light blue. 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 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 cluster programming and electronic messages
received by the cluster from the Powertrain Control
Module (PCM) over the Programmable Communica-
tions Interface (PCI) data bus. The speedometer is an
8J - 36 INSTRUMENT CLUSTERDR
SERVICE 4WD INDICATOR (Continued)

sages to the Front Control Module (FCM) over the
Programmable Communications Interface (PCI) data
bus and flashes the turn signal indicators on and off
accordingly. For further diagnosis of the turn signal
indicators or the instrument cluster circuitry that
controls the indicators, (Refer to 8 - ELECTRICAL/
INSTRUMENT CLUSTER - DIAGNOSIS AND
TESTING). For proper diagnosis of the turn signal
and hazard warning system, the multi-function
switch, the FCM, the PCI data bus, or the electronic
message inputs to the instrument cluster that control
the turn signal indicators, a DRBIIItscan tool is
required. Refer to the appropriate diagnostic infor-
mation.
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 electronically disabled. The upshift indicator con-
sists of an upward pointed arrow icon, which appears
on the right side of the electronic gear selector indi-
cator 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 speedom-
eter 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 icon
appears in a blue-green color and at the same light-
ing level as the odometer/trip odometer information
when it is illuminated by 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 manual transmission
should be shifted to the next highest gear in order to
achieve the best fuel economy. This indicator is con-
trolled by the instrument cluster circuit board based
upon cluster programming and electronic 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
with a diesel engine over the Programmable Commu-
nications Interface (PCI) data bus. The upshift indi-
cator is completely controlled by the instrument
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 indi-
cator will always be off when the ignition switch is inany 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 upshift indicator for the following
reasons:
²Upshift Lamp-On Message- Each time the
cluster receives an upshift lamp-on message from the
PCM or ECM indicating the engine speed and load
conditions are right for a transmission upshift to
occur, the upshift indicator is illuminated. The indi-
cator remains illuminated until the cluster receives
an upshift lamp-off message from the PCM or ECM,
or until the ignition switch is turned to the Off posi-
tion, whichever occurs first. The PCM or ECM 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 upshift 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.
On vehicles with a gasoline engine, the PCM con-
tinually monitors the engine speed and load condi-
tions to determine the proper fuel and ignition
requirements. On vehicles with a diesel engine, the
ECM continually monitors the engine speed and load
conditions to determine the proper fuel requirements.
The PCM or ECM then sends the proper upshift indi-
cator lamp-on and lamp-off messages to the instru-
ment cluster. For further diagnosis of the upshift
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 PCM, the
ECM, the PCI data bus, or the electronic message
inputs to the instrument cluster that control the
upshift indicator, a DRBIIItscan tool is required.
Refer to the appropriate diagnostic information.
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,
above the fuel gauge. The voltage 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
8J - 40 INSTRUMENT CLUSTERDR
TURN SIGNAL INDICATOR (Continued)

OPERATION
The backup lamp switch controls the flow of bat-
tery voltage to the backup lamp bulbs through an
output on the back-up lamp feed circuit. The switch
plunger is mechanically actuated by the gearshift
mechanism within the transmission, which will
depress the switch plunger and close the switch con-
tacts whenever the reverse gear has been selected.
The switch receives battery voltage through a fuse in
the Integrated Power Module (IPM) on a fused igni-
tion switch output (run) circuit whenever the ignition
switch is in the On position. A take out of the engine
wire harness connects the backup lamp switch to the
vehicle electrical system. The backup lamp switch
and circuits can be tested using conventional diag-
nostic tools and methods.
DIAGNOSIS AND TESTING - BACKUP LAMP
SWITCH
(1) Disconnect and isolate the battery negative
cable.
(2) Raise and support the vehicle.
(3) Locate and disconnect the engine wire harness
connector for the backup lamp switch.
(4) Check for continuity between the two terminal
pins in the backup lamp switch connector.
(a) With the gear selector lever in the Reverse
position, there should be continuity.
(b) With the gear selector lever in any position
other than Reverse, there should be no continuity.
BRAKE LAMP
REMOVAL
(1) Disconnect and isolate the negative battery
cable.
(2) Remove the tail lamp unit (Refer to 8 - ELEC-
TRICAL/LAMPS/LIGHTING - EXTERIOR/TAIL
LAMP UNIT - REMOVAL).
(3) Remove the bulb back plate from the tail lamp
unit.
(4) Remove the bulb from the back plate.
INSTALLATION
(1) Install the bulb into the back plate.
(2) Install the bulb back plate to the tail lamp
unit.
(3) Install the tail lamp unit (Refer to 8 - ELEC-
TRICAL/LAMPS/LIGHTING - EXTERIOR/TAIL
LAMP UNIT - INSTALLATION).
(4) Connect the negative battery cable.
BRAKE LAMP SWITCH
DESCRIPTION
The plunger type brake lamp switch is mounted on
a bracket attached to the base of the steering col-
umn, under the instrument panel.
CAUTION: The switch can only be adjusted during
initial installation. If the switch is not adjusted prop-
erly a new switch must be installed.
OPERATION
The brake lamp switch is hard wired to the Center
High Mount Stop Lamp (CHMSL) and also moni-
tored by the Instrument Cluster for use by the brake
lamp, speed control brake sensor circuits and elec-
tronic brake distribution (EBD). The brake lamp cir-
cuit is open until the plunger is depressed. The speed
control and brake sensor circuits are closed until the
plunger is depressed. When the brake lamp switch
transitions, the CHMSL transitions and instrument
cluster transmits a brake applied/released message
on the bus. The Integrated Power Module (IPM) will
then transition the brake lamps.
When the brake light switch is activated, the Pow-
ertrain Control Module (PCM) receives an input indi-
cating that the brakes are being applied. After
receiving this input, the PCM maintains idle speed to
a scheduled rpm through control of the Idle Air Con-
trol (IAC) motor. The brake switch input is also used
to disable vent and vacuum solenoid output signals
to the speed control servo.
Fig. 1 Backup Lamp Switch - Typical
1 - MANUAL TRANSMISSION
2 - BACKUP LAMP SWITCH
3 - ENGINE WIRE HARNESS
8L - 8 LAMPS/LIGHTING - EXTERIORDR
BACKUP LAMP SWITCH (Continued)

Vehicles equipped with the speed control option use
a dual function brake lamp switch. The PCM moni-
tors the state of the dual function brake lamp switch.
The brake switch is equipped with three sets of
contacts, one normally open and the other two nor-
mally closed (brakes disengaged). The PCM sends a
12 volt signal to one of the normally closed contacts
in the brake switch, which is returned to the PCM as
a brake switch state signal. With the contacts closed,
the 12 volt signal is pulled to ground causing the sig-
nal to go low. The low voltage signal, monitored by
the PCM, indicates that the brakes are not applied.
When the brakes are applied, the contacts open,
causing the PCM's output brake signal to go high,
disengaging the speed control, cutting off PCM power
to the speed control solenoids.
The second set of normally closed contacts supplies
12 volts from the PCM any time speed control is
turned on. Through the brake switch, voltage is
routed to the speed control servo solenoids. The
speed control solenoids (vacuum, vent and dump) are
provided this voltage any time the speed control is
ON and the brakes are disengaged.
When the driver applies the brakes, the contacts
open and voltage is interrupted to the solenoids. The
normally open contacts are fed battery voltage. When
the brakes are applied, battery voltage is supplied to
the brake lamps.
The brake lamp switch can only be adjusted once.
That is at the initial installation of the switch. If the
switch is not adjusted properly or has been removed,
a new switch must be installed and adjusted.
DIAGNOSIS AND TESTING - BRAKE LAMP
SWITCH
The brake lamp switch can be tested with an ohm-
meter. The ohmmeter is used to check continuity
between the pin terminals (Fig. 2).
SWITCH CIRCUIT IDENTIFICATION
²Terminals 1 and 2: brake lamp circuit
²Terminals 3 and 4: RWAL/ABS module and Pow-
ertrain Control Module (PCM) circuit
²Terminals 5 and 6: speed control circuit
SWITCH CONTINUITY TEST
NOTE: Disconnect switch harness before testing
switch continuity.
With switch plunger extended, attach test leads to
pins 1 and 2. Replace switch if meter indicates no
continuity.
With switch plunger retracted, attach test leads to
pins 3 and 4. Replace switch if meter indicates no
continuity.With switch plunger retracted, attach test leads to
pins 5 and 6. Replace switch if meter indicates no
continuity.
REMOVAL
(1) Disconnect the switch harness (Fig. 3).
(2) Press and hold the brake pedal in applied posi-
tion.
(3) Rotate the switch counterclockwise about 30É to
align the switch lock tab with the notch in bracket.
(4) Pull the switch rearward out of the mounting
bracket and release the brake pedal.
Fig. 2 Brake Lamp Switch Terminal Identification
1 - TERMINAL PINS
2 - PLUNGER TEST POSITIONS
Fig. 3 Brake Lamp Switch & Bracket
1 - RELEASE LEVER
2 - BRACKET
3 - BRAKE PEDAL SUPPORT
4 - BRAKE LAMP SWITCH
DRLAMPS/LIGHTING - EXTERIOR 8L - 9
BRAKE LAMP SWITCH (Continued)