Raider 2WD V6-3.7L (2008)
Temperature Warning Indicator - A/T: Description and Operation
TRANS TEMP INDICATOR
DESCRIPTION
A transmission over-temperature indicator is standard equipment on all instrument clusters. However, on vehicles not equipped with an optional
automatic transmission, this indicator is electronically disabled. This indicator is located in the center of the speedometer, in the area above and to the
right of the speedometer needle hub.
The transmission over-temperature indicator consists of a stencil-like cutout of the International Control and Display Symbol icon for Transmission
Temperature in the opaque layer of the instrument cluster overlay. The dark outer layer of the overlay prevents the indicator from being clearly visible
when it is not illuminated. A red Light Emitting Diode (LED) behind the cutout in the opaque layer of the overlay causes the indicator to appear in red
through the translucent outer layer of the overlay when it is illuminated from behind by the LED, which is soldered onto the instrument cluster electronic
circuit board. The transmission over-temperature indicator is serviced as a unit with the instrument cluster.
OPERATION
The transmission over-temperature indicator gives an indication to the vehicle operator when the transmission fluid temperature is excessive, which may
lead to accelerated transmission component wear or failure. This indicator is controlled by a transistor on 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 transmission over-temperature indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit, and that logic
will only allow this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit.
Therefore, the LED will always be OFF when the ignition switch is in any position except ON or START. The LED only illuminates when it is provided
a path to ground by the instrument cluster transistor. The instrument cluster will turn ON the transmission over-temperature indicator for the following
reasons:
-
Bulb Test - Each time the ignition switch is turned to the ON position the transmission over-temperature indicator is illuminated for about two
seconds as a bulb test.
-
Trans Over-Temp Indicator Lamp-On Message - Each time the cluster receives an electronic trans over-temp indicator lamp-ON message from
the PCM indicating that the transmission fluid temperature is 135 °C (275 °F) or higher, the indicator will be illuminated and a single chime tone
is sounded. The indicator remains illuminated until the cluster receives a lamp-OFF message from the PCM, 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 indicator is cycled OFF and
then ON again by the appropriate lamp-ON and lamp-OFF messages from the PCM.
-
Actuator Test - Each time the cluster is put through the actuator test, the transmission over-temperature indicator will be turned ON, then OFF
again during the bulb check portion of the test to confirm the functionality of the LED and the cluster control circuitry.
The PCM continually monitors the transmission temperature sensor to determine the transmission operating condition. The PCM then sends the proper
lamp-ON or lamp-OFF message to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN). If the
instrument cluster illuminates the transmission over-temperature indicator due to a high transmission oil temperature condition, it may indicate that the
transmission or the transmission cooling system are being overloaded, or that they require service.
For proper diagnosis of the transmission temperature sensor, the PCM, the EMIC, the CAN data bus or the electronic communication related to
transmission over-temperature indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.
