Parking Brake Switch - Operation

OPERATION

The hand-operated park brake switch is a normally closed, mechanically actuated leaf contact switch that is operated by the hand park brake lever mechanism. The switch is grounded through its mounting to the park brake lever mechanism and provides a ground input to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) on a park brake switch sense circuit whenever the park brake is applied, and opens this circuit whenever the park brake is released. The park brake switch sense input to the EMIC is used as a logic input by the EMIC for control of the brake indicator and may also be used as a logic input for other electronic features in the vehicle.

The park brake switch as well as the hard wired inputs and outputs of the switch may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the electronic controls and communication between other modules and devices that rely upon inputs from the park brake switch. The most reliable, efficient, and accurate means to diagnose the electronic controls and communication related to park brake switch operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.