Dakota 4WD V8-4.7L (2009)
Four Wheel Drive Indicator Lamp: Description and Operation
4WD Low Indicator - Operation
4WD LOW INDICATOR
The 4WD low indicator gives an indication to the vehicle operator when the electronic transfer case has been shifted into the 4WD low 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 low 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 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 4WD low indicator for the following reasons:
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4WD Low Indicator Lamp-On Message- Each time the cluster receives an electronic 4WD low 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 low indicator turns on, then off again during the LED 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 low
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 low 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 low indicator operation. Refer to the appropriate diagnostic information.
