Transmission Temperature Indicator

WARNING: This page is about a different car, the 2013 Dodge Avenger and 2013 Chrysler 200. However, it is still accessible from the selected car via links, so may be relevant.

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 CAN data bus. 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.

The transmission over-temperature indicator LED is completely controlled by the instrument cluster logic circuit. This logic only allows the indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the LED is always 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 turns on the transmission over-temperature indicator for the following reasons:

Trans Over-Temp Indicator Lamp-On Message - Each time the cluster receives an electronic transmission over temp indicator lamp-on message from the PCM indicating that the transmission fluid temperature is 135 °C (275 °F) or higher, the indicator illuminates 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 only repeats 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.

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 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 further diagnosis of the transmission over-temperature indicator or the instrument cluster circuitry that controls the LED. Refer to DIAGNOSIS AND TESTING .