Theory Of Operation
The horn switch is connected to the Right Steering Wheel Switch. The horn switch status is transferred from the Right Steering Wheel Switch to the Cluster through the Local Interface Network (LIN) bus, a serial sub-bus.
When the Cluster detects that the brake pedal is pressed by the driver, the Cluster delivers 12 volts to the Brake Transmission Shift Interlock Solenoid (BTSI) on the K321 circuit. The driver is then able to shift out of park. When the brake pedal is released, the voltage on the K321 circuit drops to 0 volts.