Parking Brake Warning Switch: Description and Operation
PARK BRAKE SWITCHDESCRIPTION
The park brake switch (1) is located on the park brake lever mechanism on the floor panel transmission tunnel below the center floor console. This switch includes a spade-type output terminal (3) that connects the switch to the vehicle electrical system through a dedicated take out and connector of the instrument panel wire harness. The output terminal is integral to the stationary contact within a molded plastic insulator.
A locating tab on the insulator engages a slot in the park brake lever mechanism for positive switch location. External to the insulator is a movable leaf contact with an integral grounding lug (2) on one end and an integral actuating lever and follower (4) on the opposite end. The switch is secured to and grounded by a single screw to the park brake lever mechanism. The park brake switch cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.
OPERATION
The park brake switch is a normally closed, mechanically actuated leaf contact switch that is operated by the 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 sometimes referred to as the Cab Control 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 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 can be diagnosed using conventional diagnostic tools and methods. However, proper testing of the EMIC processing of the park brake switch sense input requires the use of a diagnostic scan tool.