Commander 2WD V8-4.7L (2008)
accompany brake indicator illumination. This message indicates that the CAB has detected a low brake fluid level condition in the brake master
cylinder or that there is a problem in the brake fluid level switch or circuits.
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Park Brake Switch Input - Each time the cluster detects ground on the park brake switch sense circuit (park brake switch closed = park brake
applied or not fully released) while the ignition switch is in the ON position, the brake indicator flashes ON and OFF. The indicator continues to
flash until the park brake switch sense input to the cluster is an open circuit (park brake switch open = park brake fully released), or until the
ignition switch is turned to the OFF position, whichever occurs first.
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Antilock Brake System (ABS) Indicator Backup - If the instrument cluster detects a fault in the ABS indicator circuit it will send a message
indicating the fault to the Controller Antilock Brake (CAB), then flash the brake indicator ON and OFF. The cluster will continue to flash the
brake indicator until the ABS indicator circuit fault is resolved, or until the ignition switch is turned to the OFF position, whichever occurs first.
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Actuator Test - Each time the instrument cluster is put through the actuator test, the brake indicator will be turned ON, then OFF again during the
bulb check portion of the test to confirm the functionality of the LED and the cluster control circuitry.
The park brake switch on the park brake lever mechanism provides a hard wired ground input to the instrument cluster circuitry through the park brake
switch sense circuit whenever the park brake is applied or not fully released. The CAB continually monitors the ABS system circuits and sensors,
including the brake fluid level switch on the brake master cylinder reservoir, to decide whether the system is in good operating condition. The CAB then
sends the proper lamp-ON or lamp-OFF message to the ElectroMechanical Instrument Cluster (EMIC) (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 brake hydraulic system malfunction or that
the ABS system has become ineffective. The CAB will store a Diagnostic Trouble Code (DTC) for any malfunction it detects.
The hard wired park brake switch input to the instrument cluster may be diagnosed using conventional diagnostic tools and procedures. Refer to the
appropriate wiring information. For proper diagnosis of the brake fluid level switch, the ABS, the CAB, the EMIC, the CAN data bus or the electronic
communication related to brake indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.
