Commander 4WD V8-4.7L VIN N (2006)
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. The transmission overtemperature indication appears within the reconfigurable dot
matrix Organic Light Emitting Diode (OLED) display unit. The transmission over-temperature indicator consists of a textual TRANSMISSION OVER
TEMP message which appears in place of the compass/trip computer information in the dot matrix display.
The dot matrix OLED is soldered onto the cluster electronic circuit board, and is visible through a window with a smoked clear lens located on the lower
edge of the tachometer gauge dial face of the cluster overlay. The dark lens over the OLED prevents it from being clearly visible when it is not
illuminated. The transmission over-temperature indicator textual message appears in the same blue-green color and at the same lighting level as the
compass/trip computer information when it is illuminated by the instrument cluster electronic circuit board.
The transmission over-temperature indicator is serviced as a unit with the OLED in 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 the instrument cluster logic circuit based upon cluster
programming and electronic messages received over the Controller Area Network (CAN) data bus from the Powertrain Control Module (PCM).
The transmission over-temperature indicator function of the reconfigurable dot matrix Organic Light Emitting Diode (OLED) display unit 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 OLED transmission over-temperature indication will always be off
when the ignition switch is in any position except ON or START. The instrument cluster will turn on the transmission over-temperature indicator for the
following reasons:
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Trans Over-Temp Lamp-On Message - Each time the cluster receives a trans over-temp lamp-on message from the PCM indicating that the
transmission fluid temperature is 135° C (275° F) or higher, the transmission over-temperature indicator will be illuminated and a single chime
tone is sounded. The indicator remains illuminated until the cluster receives a trans over-temp 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
transmission over-temperature indicator is cycled off and then on again by the appropriate trans over-temp messages from the PCM.
The PCM continually monitors the transmission temperature sensor to determine the transmission operating condition. The PCM then sends the proper
trans over-temp lamp-on or lamp-off messages to the instrument cluster. If the instrument cluster illuminates the transmission over-temperature indicator
due to a high transmission oil temperature condition, it may indicate that the transmission and/or the transmission cooling system are being overloaded or
that they require service. For proper diagnosis of the transmission temperature sensor, the PCM, the CAN data bus, or the electronic message inputs to
the instrument cluster that control the transmission over-temperature indicator, a diagnostic scan tool is required.
