Commander 4WD V6-3.7L VIN K (2007)
Malfunction Indicator Lamp - Transfer Case: Description and Operation
Operation
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 Indicator Lamp-On Message - Each time the cluster receives an electronic service 4WD indicator lamp-ON message from the
FDCM, the service 4WD indicator will be illuminated. The indicator remains illuminated until the cluster receives a 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 message to the ElectroMechanical Instrument Cluster (EMIC).
For proper diagnosis of the FDCM, the EMIC, the CAN data bus or the electronic communication related to service 4WD indicator operation a
diagnostic scan tool is required. Refer to the appropriate diagnostic information.