Grand Cherokee 2WD V6-3.7L (2008)
Transmission Mode Indicator - A/T: Description and Operation
Operation
OPERATION
The electronic gear selector indicator gives an indication to the vehicle operator of the transmission gear that has been selected with the automatic
transmission gear selector lever. This indicator is controlled by the instrument cluster circuit board based upon cluster programming and electronic
messages received from the Powertrain Control Module (PCM) over the Controller Area Network (CAN) data bus.
The gear selector indicator information is displayed by the fixed segment Organic Light Emitting Diode (OLED) display unit soldered onto the
instrument cluster electronic circuit board, and the OLED will not display the gear selector indicator information after the ignition switch is turned to the
OFF position. Each time the cluster is disconnected from battery current for more than about five minutes, it must configure itself for the automatic
transmission type that is in the vehicle once it is reconnected to battery current. The instrument cluster circuitry operates the gear selector indicator to
provide the following features:
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Selected Gear Message - Each time the cluster receives an electronic selected gear message from the PCM, brackets [ ] will be illuminated
around the appropriate character in the gear selector indicator. The brackets will remain illuminated until the cluster receives a different selected
gear message, or until the ignition switch is turned to the OFF position, whichever occurs first.
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Communication Error - If the cluster fails to receive a selected gear message from the PCM within three seconds, the instrument cluster
circuitry will display all gear selector positions bracketed (selected) until a valid selected gear message is received or until the ignition switch is
turned to the OFF position, whichever occurs first.
-
Actuator Test - Each time the cluster is put through the actuator test, the odometer fixed segment OLED will display all of its characters at once
to confirm the functionality of the OLED and the cluster control circuitry.
The PCM continually monitors a hard wired multiplex input from the Transmission Range Sensor (TRS), then sends the proper message to the
ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN).
For proper diagnosis of the TRS, the PCM, the EMIC, the CAN data bus or the electronic communication related to gear selector indicator operation a
diagnostic scan tool is required. Refer to the appropriate diagnostic information.
