Dodge Ram Truck 1500-2500-3500. Manual — part 393

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Communication Error - If the cluster receives no messages from the PCM or ECM for about 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 message is received from the PCM or ECM.

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Actuator 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 continually monitors the fuel and emissions system circuits and sen-
sors to decide whether the system is in good operating condition. On vehicles with a diesel engine, the ECM con-
tinually 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 clus-
ter. For further 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 emissions systems may require
service.

For proper diagnosis of the fuel and emissions systems, the PCM, the ECM, the PCI data bus, or the electronic
message inputs to the instrument cluster that control the MIL, a diagnostic scan tool is required. Refer to the appro-
priate diagnostic information.

ODOMETER

DESCRIPTION

An odometer and trip odometer are standard equip-
ment in all instrument clusters. The odometer, trip
odometer, and engine hours information are displayed
in a common electronic, blue-green Vacuum-Fluores-
cent Display (VFD) unit. This VFD unit is soldered
onto the cluster electronic circuit board and is visible through a window with a smoked 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.

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 display 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 “TRIP” 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.
On all models except SRT-10, the engine hours information replaces the selected odometer or trip odometer infor-
mation whenever the ignition switch is in the On position and the engine is not running. The engine hours feature
is disabled on all SRT-10 models.

The odometer, trip odometer, and engine hours information is stored in the instrument cluster memory. This infor-
mation can be increased when the proper inputs are provided to the instrument cluster, but the information cannot
be decreased. The odometer can display values up to 999,999 kilometers (999,999 miles). The odometer latches at
these values, 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. Engine hours are displayed in the format, “hr9999”. The cluster will accumulate
values up to 9,999 hours before the display rolls over to zero.

The odometer display 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. The odometer also has a “Rental Car” 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 odometer VFD is illuminated 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 “Parade” 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.

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The odometer/trip odometer 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.
On all models except SRT-10, the engine hours give an indication of the cumulative engine-on time. The engine
hours feature is disabled on SRT-10 models. This indicator is controlled by the instrument cluster circuitry based
upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module
(PCM) or Engine Control Module (ECM) over the Programmable Communications Interface (PCI) data bus.

The odometer, trip odometer and engine hours information is displayed by the instrument cluster odometer Vacuum
Fluorescent Display (VFD). The odometer VFD will display the odometer information whenever the driver side front
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:

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Odometer/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).

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Engine 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 message from the
PCM is zero, the trip odometer information will be momentarily displayed, then the engine hours information
will be displayed. The VFD 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.

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Trip Odometer Reset - When the trip odometer reset switch button is pressed and held for longer than about
two seconds with the ignition switch in the On or Start position, the trip odometer will be reset to 0.0 kilometers
(miles). The VFD must be displaying the trip odometer information in order for the trip odometer information to
be reset.

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Communication 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 will display all dashes.

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Actuator Test - Each time the cluster is put through the actuator test, the odometer VFD will display 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 or the
Controller Anti-lock Brake (CAB) 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 circuitry that controls these functions, (Refer to 8 - ELECTRICAL/
INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING).

For proper diagnosis of the vehicle speed sensor, the crankshaft position sensor, the CAB, the PCM, the PCI data
bus, or the electronic message inputs to the instrument cluster that control the odometer/trip odometer, a diagnostic
scan tool is required. Refer to the appropriate diagnostic information.

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 cluster,
above the coolant temperature gauge.

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The oil pressure 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 “L” (or Low) to “H” (or High) for
gasoline engines except SRT-10. On SRT-10 models, the scale reads from “0” kPa to “700” kPa in markets where
a metric instrument cluster is specified, or from “0” psi to “100” psi in all other markets. On vehicles with a diesel
engine the scale reads from “0” kPa to “760” kPa in markets where a metric instrument cluster is specified, or from
“0” psi to “110” psi in all other markets.

An International Control and Display Symbol icon for “Engine Oil” is located on the cluster overlay, directly below the
left end of the gauge scale. On all models except SRT-10 the oil pressure gauge graphics are black against a white
field except for two red graduations at the low end of the gauge scale. On SRT-10 the gauge graphics are black
against a silver field except for a single red zone at the low end of the gauge scale. In either case, the gauge
graphics are 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-green and the red graphics still appear red. The gauge needle has
internal optical illumination. Gauge illumination is provided by replaceable incandescent bulb and holder units
located on the instrument cluster electronic circuit board. The oil pressure gauge is serviced 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 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 Con-
trol 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 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:

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Engine Oil Pressure Message - The instrument cluster circuitry restricts the oil pressure gauge needle oper-
ation in order to provide readings that are consistent with customer expectations. For all models except SRT-
10, 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. For SRT-10 models, each time the cluster receives a message from the
PCM indicating the engine oil pressure is above about 41 kPa (6 psi) the cluster moves the gauge needle in
a linear fashion to the proper relative pressure position of the gauge scale.

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Engine Oil Pressure Low Message - Each time the cluster receives three consecutive bus messages from
the PCM or ECM indicating the engine oil pressure is below about 41 kPa (6 psi), the gauge needle is moved
to the red graduations (except SRT-10) or to the red zone (SRT-10) at the far left end of the gauge scale, the
check gauges indicator is illuminated, and a single 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 cluster 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.

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Communication Error - If the cluster fails to receive an engine oil pressure message, it will hold the gauge
needle at the last indication for about ten seconds, or until the ignition switch is turned to the Off position,
whichever occurs first. After ten seconds, the cluster will move the gauge needle to the low end of the gauge
scale.

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Actuator Test - Each time the cluster is put through the actuator test, the oil pressure 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 circuitry.

On vehicles with a gasoline engine, the PCM continually 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 cluster. 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

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turns on the check gauges indicator 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 instrument cluster that control the oil pressure gauge, a diagnostic scan tool is required.
Refer to the appropriate diagnostic information.

GAUGE-ENGINE OIL TEMPERATURE

DESCRIPTION

An oil temperature gauge (1) is standard equipment
on all SRT-10 models. This electronic, analog gauge is
located in the lower end of the left A-pillar trim molding
below the grab handle (2), in clear view of the vehicle
operator. The gauge dial face is visible through a clear
plastic lens, which is secured to the gauge housing
with a silver anodized trim ring. The remainder of the
gauge, including the mounting provisions and the elec-
trical connections, are concealed behind the left A-pil-
lar trim molding.

The molded plastic housing at the rear of the gauge
protects the electronic circuitry of the gauge and has
two mounting studs, which are secured by nuts to a
molded plastic mounting bracket screwed to the back
of the A-pillar trim molding. A short pigtail wire with a
connector extends from the back of the gauge housing
and connects the gauge to the vehicle electrical sys-
tem through a take out and connector of the instru-
ment panel wire harness.

The oil temperature gauge consists of a movable
gauge needle or pointer with a 270 degree sweep that
is controlled by the electronic gauge circuitry. The
gauge overlay reads left-to-right from “60” to “150”
with “°C” indicated directly below the low (left) end of
the scale in markets where a metric instrument cluster
is specified, or from “140” to “300” with “°F” indicated
directly below the left end of the scale for all other
markets. The text “OIL TEMP” is imprinted on the cen-
ter of the gauge overlay below the hub of the gauge
needle, while the text “SRT” is imprinted above the
hub of the gauge needle. The gauge graphics are
black against a silver field except for a single red zone
at the high (right) end of the gauge scale and are
clearly visible in daylight.

General illumination lighting for the gauge is provided by a Light Emitting Diode (LED) that is soldered onto the
gauge circuit board. The gauge overlay is a laminated plastic unit. The dark, visible, outer surface of the overlay is
marked with the gauge dial face and graduations, but this layer is also translucent. The underlying layer of the
overlay is opaque and allows light from the LED on the circuit board behind it to be visible through the outer layer
of the overlay only through predetermined stencil-like cutouts. When illuminated from behind by the panel lamps

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