Commander 4WD V8-4.7L VIN N (2006)
Four Wheel Drive Indicator Lamp: Description and Operation
SERVICE 4WD INDICATOR
DESCRIPTION
A service 4WD indicator is standard equipment on all instrument clusters. However, on vehicles not equipped with the optional four-wheel drive system
and electronically shifted transfer case, this indicator is electronically disabled. The service 4WD indication appears within the reconfigurable dot matrix
Organic Light Emitting Diode (OLED) display unit. The service 4WD indicator consists of a textual SERVICE 4WD SYSTEM message which appears
in place of the compass/trip computer information in the dot matrix display.
The dot matrix OLED is soldered onto the cluster electronic circuit board, and is visible through a window with a smoked clear lens located on the lower
edge of the tachometer gauge dial face of the cluster overlay. The dark lens over the OLED prevents it from being clearly visible when it is not
illuminated. The service 4WD indicator textual message appears in the same blue-green color and at the same lighting level as the compass/trip computer
information when it is illuminated by the instrument cluster electronic circuit board.
The service 4WD indicator is serviced as a unit with the OLED in the instrument cluster.
OPERATION
The service 4WD indicator gives an indication to the vehicle operator when the Final Drive Control Module (FDCM) has recorded a Diagnostic Trouble
Code (DTC) for an electronic transfer case circuit or component malfunction. This indicator is controlled by the instrument cluster logic circuit based
upon cluster programming and electronic messages received by the cluster from the FDCM over the Controller Area Network (CAN) data bus.
The service 4WD 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 service 4WD indication will always be off when the ignition switch is in any
position except ON or START. The instrument cluster will turn on the service 4WD indicator for the following reasons:
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Service 4WD Lamp-On Message - Each time the cluster receives a service 4WD lamp-on message from the FDCM, the service 4WD indicator
will be illuminated. The indicator remains illuminated until the cluster receives a service 4WD lamp-off message from the FDCM, or until the
ignition switch is turned to the OFF position, whichever occurs first.
The FDCM continually monitors the electronic transfer case control circuits and transfer case shift motor/mode sensor assembly to determine the
condition of the system. The FDCM then sends the proper lamp-on or lamp-off messages to the instrument cluster. For proper diagnosis of the FDCM,
the CAN data bus, or the electronic message inputs to the instrument cluster that control the service 4WD indicator, a diagnostic scan tool is required.
