Dakota 4WD V8-4.7L (2009)
Four Wheel Drive Indicator Lamp: Description and Operation
4WD Indicator - Operation
4WD INDICATOR
The 4WD indicator gives an indication to the vehicle operator when the electronic transfer case has been shifted into a 4WD mode. 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 Front Control Module (FCM) over the Controller Area Network (CAN) data bus.
The 4WD indicator Light Emitting Diode (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 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 turns on the 4WD indicator for the following reasons:
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4WD Indicator Lamp-On Message - Each time the cluster receives an electronic 4WD indicator lamp-on message from the FCM, the indicator
illuminates. The indicator remains illuminated until the cluster receives a lamp-off message from the FCM, or until the ignition switch is turned to
the OFF position, whichever occurs first.
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Self Test - Each time the cluster is put through the self test, the 4WD 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 FCM continually monitors the electronic transfer case through the transfer case shift motor/mode sensor assembly to determine when the 4WD mode
is engaged. The FCM then sends the proper lamp-on or lamp-off message to the instrument cluster also known as the Cab Compartment Node (CCN).
For further diagnosis of the 4WD indicator or the instrument cluster circuitry that controls the LED, See: Instrument Panel, Gauges and Warning
Indicators/Instrument Cluster / Carrier/Testing and Inspection/Component Tests and General Diagnostics.
Use a diagnostic scan tool for proper diagnosis of the transfer case shift motor/mode sensor, the FCM, the CCN, the CAN data bus or the electronic
communication related to 4WD indicator operation. Refer to the appropriate diagnostic information.
