Commander 2WD V8-4.7L (2008)
Temperature Warning Indicator - A/T: Description and Operation
Operation
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 Front Control Module (FCM).
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:
-
Trans Over-Temp Indicator Lamp-On Message - Each time the cluster receives an electronic trans over-temp indicator lamp-ON message
from the FCM indicating that the 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 for about five seconds, until the cluster receives a lamp-OFF message from
the FCM, until the cluster arbitrator logic determines that another display request has priority, 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 FCM.
The FCM continually monitors the transmission temperature sensor to determine the transmission operating condition. The FCM 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 FCM, 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.
