Grand Caravan V6-3.8L (2009)
Brake Light Switch: Description and Operation
Stop Lamp Switch - Operation
OPERATION
The brake lamp switch controls three independent circuits. These circuits are described as follows:
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Brake Lamp Switch Circuit - A normally open brake lamp switch circuit receives a battery voltage input, and supplies this battery voltage to the
Center High Mounted Stop Lamp (CHMSL) and the Totally Integrated Power Module (TIPM) on a brake lamp switch output circuit only when
the brake pedal is depressed (brake lamp switch plunger released).
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Brake Lamp Switch Signal Circuit - A normally closed brake lamp switch signal circuit receives a direct path to ground, and supplies this
ground input to the Powertrain Control Module (PCM) on a brake signal 1 circuit only when the brake pedal is released (brake lamp switch
plunger is depressed).
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Speed Control Circuit - A normally closed speed control circuit receives a battery voltage input from the Totally Integrated Power Module
(TIPM) on an ignition run/start control output circuit, and supplies this battery voltage to the PCM on a brake signal 2 circuit only when the brake
pedal is released (brake lamp switch plunger is depressed).
The PCM sends electronic brake lamp switch status messages to other electronic modules in the vehicle over the Controller Area Network (CAN) data
bus for use as an additional logic input for controlling many other vehicle functions and features.
The components of the self-adjusting brake switch plunger consist of a two-piece telescoping plunger, a split plunger locking collar, and a release wedge.
The release lever has a shaft with a wedge that spreads the plunger locking collar to an open or released position. After the switch is installed and the
brake pedal is released, the plunger telescopes to the correct adjustment position. When the release lever is moved to the release position, the wedge is
disengaged from the locking collar causing the collar to apply a clamping pressure to the two plunger halves, fixing the plunger length.
The brake lamp 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 that provide some features related to brake lamp switch operation. The most reliable, efficient and accurate means to
diagnose the electronic controls and communication related to brake lamp switch operation requires the use of a diagnostic scan tool. Refer to the
appropriate diagnostic information.
