is specified, or from “140”° F to “245”° F in all other markets. An International Control and Display Symbol icon for
“Engine Coolant Temperature” is located on the cluster overlay, directly below the left end of the gauge scale.
On all models except SRT-10 the engine coolant temperature gauge graphics are black against a white field except
for two red graduations at the high 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 high 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 gauge 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 engine coolant temperature gauge is serviced as
a unit with the instrument cluster.
OPERATION
The engine coolant temperature gauge gives an indication to the vehicle operator of the engine coolant temperature.
This gauge is controlled by 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 Programma-
ble Communications Interface (PCI) data bus.
The engine coolant temperature 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:
•
Engine Temperature Message - Each time the cluster receives a message from the PCM or ECM indicating
the engine coolant temperature is between the low end of normal [about 54° C (130° F) for gasoline engines
except SRT-10, or about 60° C (140° F) for SRT-10 and diesel engines] and the high end of normal [about
122° C (252° F) for gasoline engines, about or about 116° C (240° F) for diesel engines], the gauge needle is
moved to the actual relative temperature position on the gauge scale.
•
Engine Temperature Low Message - Each time the cluster receives a message from the PCM or ECM indi-
cating the engine coolant temperature is below the low end of normal [about 54° C (130° F) for gasoline
engines except SRT-10, or about 60° C (140° F) for SRT-10 and diesel engines], the gauge needle is held at
the graduation on the far left end of the gauge scale. The gauge needle remains at the left end of the gauge
scale until the cluster receives a message from the PCM or ECM indicating that the engine temperature is
above about 54° C (130° F) for gasoline engines except SRT-10, or about 60° C (140° F) for SRT-10 and
diesel engines, or until the ignition switch is turned to the Off position, whichever occurs first.
•
Engine Temperature High Message - Each time the cluster receives three consecutive bus messages from
the PCM or ECM indicating the engine coolant temperature is above about 122° C (252° F) for gasoline
engines, or about 116° C (240° F) for diesel engines, the gauge needle is moved into the red zone at the far
right end of gauge scale, the check gauges indicator is illuminated, and a single chime tone is sounded. The
gauge needle remains in the red zone and the check gauges indicator remains illuminated until the cluster
receives a message from the PCM or ECM indicating that the engine temperature is below about 122° C (252°
F) for gasoline engines, or about 116° C (240° F) for diesel engines, or until the ignition switch is turned to the
Off position, whichever occurs first. The chime tone feature will only repeat during the same ignition cycle if the
check gauges indicator is cycled off and then on again by the appropriate engine temperature messages from
the PCM or ECM.
•
Communication Error - If the cluster fails to receive an engine temperature 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.
•
Actuator Test - Each time the cluster is put through the actuator test, the engine coolant temperature 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 circuitry.
On vehicles with a gasoline engine, the PCM continually monitors the engine coolant temperature sensor to deter-
mine the engine operating temperature. On vehicles with a diesel engine, the ECM continually monitors the engine
coolant temperature sensor to determine the engine operating temperature. The PCM or ECM then sends the
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INSTRUMENT CLUSTER -SERVICE INFORMATION
DR/DH