Dakota 2WD V8-4.7L VIN J (2005)
Temperature Gauge: Description and Operation
An engine coolant temperature gauge is standard equipment on all instrument clusters. This gauge is part of the minor gauge set with the fuel gauge
located on the left side of the instrument cluster, just left of the speedometer. The gauge consists of a movable gauge needle or pointer controlled by the
instrument cluster circuitry and a fixed 90 degree gauge scale on the cluster overlay that reads bottom-to-top from "C" (or Cold) to "H" (or Hot). An
International Control and Display Symbol icon for "Engine Coolant Temperature" is located on the cluster overlay, directly below the bottom end of the
scale.
The engine coolant temperature gauge graphics are black against a white field except for a single red graduation at the high 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 gauge dial face appears blue-green with the black graphics silhouetted against the
illuminated background and the red graphics and the red gauge needle still appear red. Gauge illumination is provided by an integral electro-luminescent
lamp that is serviced as a unit with the instrument cluster. The engine coolant temperature gauge is serviced as a unit with the instrument cluster.
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 messages received by the cluster from the Powertrain Control Module
(PCM) over the Controller Area Network (CAN) 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:
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Engine Temperature Message - Each time the cluster receives a message from the PCM indicating the engine coolant temperature is between the
low end of normal [about 54° C (130° F)] and the high end of normal [about 122° C (252° F)], the gauge needle is moved to the actual relative
temperature position on the gauge scale.
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Engine Temperature Low Message - Each time the cluster receives a message from the PCM indicating the engine coolant temperature is below
the low end of normal [about 54° C (130° F)], the gauge needle is held at the "C" increment at low end of the gauge scale. The gauge needle
remains at the low end of the gauge scale until the cluster receives a message from the PCM indicating that the engine temperature is above about
54° C (130° F), or until the ignition switch is turned to the Off position, whichever occurs first.
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Engine Temperature High Message - Each time the cluster receives a message from the PCM indicating the engine coolant temperature is above
about 122° C (252° F), the gauge needle is moved into the red zone on the gauge scale, the engine temperature indicator is illuminated, and a
single chime tone is sounded. The gauge needle remains in the red zone and the engine temperature indicator remains illuminated until the cluster
receives a message from the PCM indicating that the engine temperature is below about 122° C (252° F), 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 engine temperature indicator
is cycled off and then on again by the appropriate engine temperature messages from the PCM.
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Communication Error - If the cluster fails to receive an engine temperature message, it will hold the gauge needle at the last indication for about
five seconds 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 low end of the gauge scale.
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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.
The PCM continually monitors the engine coolant temperature sensor to determine the engine operating temperature. The PCM then sends the proper
engine coolant temperature messages to the instrument cluster. For further diagnosis of the engine coolant temperature gauge or the instrument cluster
circuitry that controls the gauge, refer to testing. If the instrument cluster turns on the engine temperature indicator due to a high engine temperature
gauge reading, it may indicate that the engine or the engine cooling system requires service.
For proper diagnosis of the engine coolant temperature sensor, the PCM, the CAN data bus, or the electronic message inputs to the instrument cluster
that control the engine coolant temperature gauge, a diagnostic scan tool is required.
