OPERATION

The four-wheel drive indicator gives an indication to the vehicle operator when a four-wheel drive (4WD) mode of the transfer case is selected. This indicator is controlled by the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster over the Controller Area Network (CAN) data bus.

The four-wheel drive indicator 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 indicator will always be OFF when the ignition switch is in any position except ON or START. The indicator only illuminates when it is energized by the instrument cluster logic circuit. The instrument cluster will turn ON the cruise indicator for the following reasons:

• Four-Wheel Drive Indicator Lamp-On Message - Each time the cluster receives an electronic four-wheel drive indicator lamp-ON message over the CAN data bus indicating that a four-wheel drive mode is selected, the four-wheel drive indicator is illuminated. The indicator remains illuminated until the cluster receives a lamp-OFF message over the CAN bus, 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 four-wheel drive indicator will be turned ON, then OFF again during the Vacuum Fluorescent Display (VFD) portion of the test in order to confirm the functionality of the VFD and the cluster control circuitry.

The ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) continually monitors messages over the CAN bus to determine when the four-wheel drive indicator should be activated or deactivated.

For proper diagnosis of the four-wheel drive switch, the EMIC, the CAN data bus or the electronic communication related to four-wheel drive indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.