Brake Lamp: Description and Operation
BRAKE LAMPSThe brake (or stop) lamps and the Center High Mounted Stop Lamp (CHMSL) each have a path to ground at all times through a takeout and eyelet terminal of the body wire harness that is secured by a ground screw to the body sheet metal within the passenger compartment. The brake lamps and CHMSL receive battery voltage on the brake lamp switch feed circuit when the brake lamp switch is closed by the brake pedal arm. On vehicles so equipped, the FCM controls trailer brake lamps through the trailer tow relays based upon this input from the brake lamp switch.