Dodge Dakota 2001, Service Manual

Page: 446 / 2307

cator is illuminated from behind by a Light Emitting
Diode (LED) soldered onto the instrument cluster
electronic circuit board. The upshift indicator is ser-
viced as a unit with the instrument cluster.
OPERATION
The upshift indicator gives an indication to the
vehicle operator when the transmission should be
shifted to the next highest gear in order to achieve
the best fuel economy. This indicator is controlled by
a transistor on the instrument cluster circuit board
based upon cluster programming and electronic mes-
sages received by the cluster from the Powertrain
Control Module (PCM) over the Programmable Com-
munications Interface (PCI) data bus. The upshift
indicator Light Emitting Diode (LED) receives bat-
tery current on the instrument cluster electronic cir-
cuit board through the fused ignition switch output
(run-start) circuit whenever the ignition switch is in
the On or Start positions; therefore, the indicator will
always be off when the ignition switch is in any posi-
tion except On or Start. The LED only illuminates
when it is provided a path to ground by the instru-
ment cluster transistor. On models not equipped with
a manual transmission, a unique version of the
instrument cluster is used that does not include the
upshift indicator. The instrument cluster will turn on
the upshift indicator for the following reasons:
•
Bulb Test - Each time the ignition switch is
turned to the On position the upshift indicator is illu-
minated for about two seconds as a bulb test.
•
Upshift Lamp-On Message - Each time the
cluster receives an upshift lamp-on message from the
PCM indicating the engine speed and load conditions
are right for a transmission upshift to occur, the
upshift
indicator is illuminated. The indicator
remains illuminated until the cluster receives an
upshift lamp-off message from the PCM or until the
ignition switch is turned to the Off position, which-
ever occurs first. The PCM will normally send an
upshift lamp-off message three to five seconds after a
lamp-on message, if an upshift is not performed. The
indicator will then remain off until the vehicle stops
accelerating and is brought back into the range of
indicator operation, or until the transmission is
shifted into another gear.
•
Actuator Test - Each time the cluster is put
through the actuator test, the indicator will be
turned on, then off again during the bulb check por-
tion of the test to confirm the functionality of the
indicator and the cluster control circuitry.
The PCM continually monitors the engine speed
and load conditions to determine the proper fuel and
ignition requirements. The PCM then sends the
proper messages to the instrument cluster. For fur-
ther diagnosis of the upshift indicator or the instru-
ment cluster circuitry that controls the indicator,
(Refer to 8 - ELECTRICAL/INSTRUMENT CLUS-
TER - DIAGNOSIS AND TESTING). For proper
diagnosis of the PCM, the PCI data bus, or the mes-
sage inputs to the instrument cluster that control the
upshift indicator, a DRBIII
t
scan 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 temperature gauge. The voltage gauge con-
sists of a movable gauge needle or pointer controlled
by the instrument cluster circuitry and a fixed 90
degree scale on the cluster overlay that reads left-to-
right from “L” (or Low) to “H” (or High). An Interna-
tional Control and Display Symbol icon for “Battery
Charging Condition” is located on the cluster overlay,
in the center of the gauge directly above the hub of
the gauge needle. The voltage gauge graphics are
white against a black field except for a single red
graduation at each end of the gauge scale, making
them clearly visible within the instrument cluster in
daylight. When illuminated from behind by the panel
lamps dimmer controlled cluster illumination lighting
with the exterior lamps turned On, the white graph-
ics appear blue-green and the red graphics appear
red. The orange gauge needle is internally illumi-
nated. Gauge illumination is provided by replaceable
incandescent bulb and bulb holder units located on
the instrument cluster electronic circuit board. The
voltage gauge is serviced as a unit with the instru-
ment cluster.
OPERATION
The voltage gauge gives an indication to the vehi-
cle operator of the electrical system voltage. This
gauge is controlled by the instrument cluster circuit
board based upon cluster programming and elec-
tronic messages received by the cluster from the
Powertrain Control Module (PCM) over the Program-
mable Communications Interface (PCI) data bus. The
voltage 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 igni-
tion switch is in the On or Start positions. The clus-
ter 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 pro-
vides the following features:
AN
INSTRUMENT CLUSTER 8J - 33
UPSHIFT INDICATOR (Continued)