Speedometer Description; Operation - Chrysler Vehicle User Manual

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SKIS INDICATOR (Continued)
from the SKIM or until the ignition switch is turned
to the Off position, whichever occurs first.
• Actuator Test - Each time the cluster is put
through the actuator test, the SKIS 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 SKIM performs a self-test each time the igni-
tion switch is turned to the On position to decide
whether the system is in good operating condition.
The SKIM then sends the proper SKIS lamp-on or
lamp-off messages to the instrument cluster. For fur-
ther diagnosis of the SKIS indicator or the instru-
ment cluster circuitry that controls the indicator,
(Refer to 8 - ELECTRICAL/INSTRUMENT CLUS-
TER - DIAGNOSIS AND TESTING). If the instru-
ment cluster turns on the SKIS indicator after the
bulb test, either solid or flashing, it indicates that a
SKIS malfunction has occurred or that the SKIS is
inoperative. For proper diagnosis of the SKIS, the
PCI data bus, or the electronic message inputs to the
instrument cluster that control the SKIS indicator, a
DRBIII scan tool is required. Refer to the appropri-
ate 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 cluster overlay that reads left-to-right either
from "0" to "100" mph, from "0" to "110" mph, or from
"0" to "180" km/h, depending upon the requirements
of the market for which the vehicle is manufactured.
Each version also has a secondary inner scale on the
cluster overlay 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 pri-
mary scale (i.e.: MPH or km/h), followed by the unit
of measure for the secondary scale. The speedometer
graphics are white (primary scale) and blue (second-
ary scale) against a black field, 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 graphics
appear white and the blue graphics appear blue. The
orange gauge needle is internally illuminated. Gauge
illumination is provided by replaceable incandescent
bulb and bulb holder units located on the instrument
INSTRUMENT CLUSTER
cluster electronic 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
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:
• Vehicle Speed Message - Each time the clus-
ter receives a vehicle speed message from the PCM it
will calculate the correct vehicle speed reading and
position the gauge needle at that relative speed posi-
tion on the gauge scale. The cluster will receive a
new vehicle speed message and reposition the gauge
pointer accordingly about every 86 milliseconds. The
gauge needle will continue to be positioned at the
actual vehicle speed position on the gauge scale until
the ignition switch is turned to the Off position.
• Communication Error - If the cluster fails to
receive a speedometer message, it will hold the gauge
needle at the last indication for about six seconds, or
until the ignition switch is turned to the Off position,
whichever occurs first. After six seconds, the gauge
needle will return to the left end of the gauge scale.
• Actuator Test - Each time the cluster is put
through the actuator test, the gauge needle will be
swept to several calibration points on the gauge scale
in a prescribed sequence in order to confirm the func-
tionality of the gauge and the cluster control cir-
cuitry.
The PCM continually monitors the vehicle speed
sensor to determine the vehicle road speed, then
sends the proper vehicle speed messages to the
instrument cluster. For further diagnosis of the
speedometer or the instrument cluster circuitry that
controls the gauge, (Refer to 8 - ELECTRICAL/IN-
STRUMENT CLUSTER - DIAGNOSIS AND TEST-
ING). For proper diagnosis of the vehicle speed
sensor, the PCM, the PCI data bus, or the electronic
message inputs to the instrument cluster that control
the speedometer, a DRBIII
Refer to the appropriate diagnostic information.
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scan tool is required.