Dakota 2WD V8-4.7L Flex Fuel (2009)
ABS Light: Description and Operation
ABS Indicator - Operation
OPERATION
The ABS indicator gives an indication to the vehicle operator when the ABS system, or a circuit or component of the system is ineffective. 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 Controller Antilock Brake (CAB) over the Controller Area Network (CAN) data bus.
The ABS 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 is 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 turns on the ABS indicator for the following reasons:
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Bulb Test - Each time the ignition switch turns to the ON position the ABS indicator illuminates for about four seconds as a bulb test. The entire
bulb test is a function of the CAB.
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ABS Indicator Lamp-On Message - Each time the cluster receives an electronic ABS indicator lamp-on message from the CAB, the ABS
indicator illuminates. The indicator remains illuminated until the cluster receives a lamp-off message from the CAB, or until the ignition switch
turns to the OFF position, whichever occurs first.
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Communication Error - If the cluster receives no lamp-on or lamp-off messages from the CAB for five consecutive message cycles, the ABS
indicator illuminates. The indicator remains illuminated until the cluster receives a valid message from the CAB, or until the ignition switch turns
to the OFF position, whichever occurs first.
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Self Test - Each time the instrument cluster is put through the self test, the ABS indicator turns on, then off again during the bulb check portion of
the test to confirm the functionality of the LED and the cluster control circuitry.
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ABS Diagnostic Test - The ABS indicator blinks on and off by lamp-on and lamp-off messages from the CAB during the performance of the ABS
diagnostic tests.
The CAB continually monitors the ABS circuits and sensors to decide whether the system is in good operating condition. The CAB then sends the proper
lamp-on or lamp-off message to the instrument cluster, also known as the Cab Compartment Node (CCN). If the CAB sends a lamp-on message after the
bulb test, it indicates that the CAB has detected a system malfunction or that the ABS system has become ineffective. The CAB stores a Diagnostic
Trouble Code (DTC) for any malfunction it detects. Each time the ABS indicator fails to light due to an open or short in the cluster ABS indicator
circuit, the cluster sends a message notifying the CAB of the condition, then the instrument cluster and the CAB each store a DTC.
Use a diagnostic scan tool for proper diagnosis of the antilock brake system, the CAB, the CCN, the CAN data bus or the electronic communication
related to ABS indicator operation. Refer to the appropriate diagnostic information.
