Liberty 4WD V6-3.7L (2009)
Driver/Vehicle Information Display: Description and Operation
Hill Descent Indicator - Operation
OPERATION
The hill descent indicator gives an indication to the vehicle operator when the four-wheel drive transfer case gear selector is in the 4WD LOW position
and the hill descent control push button in the instrument panel switch pod has been depressed to turn the feature ON. This feature uses the grade sensing
logic of the Controller Antilock Brake (CAB) to sense the vehicle is descending a hill and employs the brake system to automatically control the hill
descent speed of the vehicle. This indicator is controlled by the instrument cluster logic circuit based upon cluster programming and electronic messages
received over the Controller Area Network (CAN) data bus from the CAB.
The hill descent indicator Light Emitting Diode (LED) 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 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 will turn ON the hill descent indicator for the following reasons:
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Hill Descent Indicator Lamp-On Message - Each time the cluster receives an electronic hill descent indicator lamp-ON message from the
CAB, the indicator will be illuminated. The indicator remains illuminated until the cluster receives a lamp-OFF message from the CAB, or until
the ignition switch is turned to the OFF position, whichever occurs first.
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Actuator Test - Each time the cluster is put through the actuator test, the hill descent indicator will be turned ON, then OFF again during the LED
portion of the test to confirm the functionality of the LED and the cluster control circuitry.
The CAB continually monitors electronic message inputs from the Totally Integrated Power Module (TIPM) and the ElectroMechanical Instrument
Cluster (EMIC) to determine the status of the four-wheel drive system and the hill descent control switch, then monitors its own internal grade sensing
logic to determine when the hill descent mode should be engaged. The CAB then sends the proper lamp-ON or lamp-OFF message to the EMIC.
For proper diagnosis of the hill descent control switch, the TIPM, the CAB, the EMIC, the CAN data bus or the electronic communication related to hill
descent indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.
